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The syndrome of primary aldosteronism produces few signs or symptoms. The diagnosis should be suspected when either spontaneous hypokalemia or easily provoked hypokalemia is found in a patient with hypertension. Hypokalemia in association with inappropriate kaliuresis, low plasma renin activity, and a high plasma aldosterone concentration/plasma renin activity ratio are the findings on initial screening tests that should suggest primary aldosteronism. The diagnosis must be confirmed by demonstrating nonsuppressible aldosterone excretion in conjunction with normal cortisol excretion. The choice of therapy is based on distinguishing unilateral from bilateral adrenal disease. With a unilateral adrenal adenoma, surgical removal reverses the hypokalemia and frequently cures the hypertension. In most patients with bilateral adrenal hyperplasia who are treated surgically, however, hypertension persists; thus, the initial treatment in these patients should be pharmacologic.

The investigation and management of pheochromocytoma have been of special interest at the Mayo Clinic since 1926, when Dr. C. H. Mayo successfully removed an adrenal tumor. Recent clinical developments include the detection of asymptomatic paroxysms of hypertension by 24-hour ambulatory monitoring, detailed characterization of catecholamine cardiomyopathy by echocardiography, and further experience with Carney's triad and other polyglandular and multiple neoplasia syndromes associated with pheochromocytoma. Refinement in interpretation of catecholamine measurements and the development of radionuclide scanning with m-[131I]iodobenzylguanidine, computed tomography, and magnetic resonance imaging have greatly enhanced our diagnostic acumen. Developments in antihypertensive drug therapy and chemotherapy have improved our management of cathecholamine hypersecretion and tumor growth, respectively, in inoperable patients and in the preparation of patients for anesthesia and surgical treatment. Flow cytometry to detect abnormal DNA histograms may prove particularly useful in predicting the malignant nature of the tumors.

Immunoassays for prostate-specific antigen (PSA) are used routinely as an aid to detect prostate cancer (PCa). PSA permits early detection of PCa but lacks specificity (1)(2). In a typical screening population of African American men ≥40 years of age and other men ≥50 years of age, ∼4% of the men with a PSA concentration >4 μg/L, which is the upper reference limit for PSA, will have prostate cancer (1). Most of these cancers can be detected using PSA. At issue, however, is the comorbidity of men with benign prostatic hyperplasia whose age and PSA concentrations are within these ranges. For example, 50% of men >60 years of age have benign prostatic hyperplasia (3), and many will have PSA >4 μg/L. The low specificity of PSA measurement as a test for PCa necessitates many prostate biopsies, of which ∼75% are negative and theoretically unnecessary. Additional biomarkers may improve sensitivity and specificity of PSA. We theorized that bioinformatics and analysis of the existing scientific literature could identify promising protein biomarker candidates that, if combined with PSA, might improve clinical sensitivity and especially specificity. The work flow we used to select candidate biomarkers is diagramed in the flow chart in Fig. 1⇓ . We searched Medline and other relevant databases from Nerac Corporation (Tolland, CT) for publications that appeared in 1999–2004 with the terms prostate cancer and markers or biomarkers or early detection or aggressiveness or staging or grading. We also used prostate-specific genes, prostate-specific proteins, and several well-known institutions and investigators in the field of prostate cancer research as search terms. Once compiled, the titles and abstracts were read to find proteins or genes documented to be differentially regulated in tissue or serum or plasma PCa samples compared with normal or benign samples. A list of >2700 citations was …

BACKGROUND This study uses the Isotope Dilution Mass Spectrometer-Traceable Modification of Diet in Renal Disease (MDRD) equation to evaluate the effects of analytic variation of serum creatinine on estimated glomerular filtration rate (eGFR). The equation was inverted to provide critical creatinine levels corresponding to eGFRs equal to 15, 30, and 60 mL/min/1.73 m(2). METHODS eGFRs were calculated for two populations of patients representing clinic outpatients and hospitalized inpatients. Simulation studies evaluated the effects of analytic bias for these populations. Differences between creatinine tests ordered on consecutive blood draws were analyzed for within-subject eGFR variation. Finally, propagation of error techniques established the relationship between creatinine imprecision and eGFR imprecision. RESULTS eGFR of 60 mL/min/1.73 m(2) corresponds to creatinine levels of 80-156 micromol/L. A 20-micromol/L negative shift of creatinine approximately doubles the percentage of patients classified in various stages of decreased renal function, whereas a positive shift approximately halves the percentage. The central 95% limits for within-subject variation of eGFR are 33% for outpatients, 38% for inpatients and 40% across the groups. eGFR imprecision is approximately 15%-20% higher than creatinine imprecision. CONCLUSIONS Small analytic changes in serum creatinine create major shifts in the distributions of eGFR, which can cause large differences in the classification of patients. The within-subject variations in eGFR over time, especially between hospital and clinic measurements, can be large. Therefore, tight control of laboratory analysis is important.

OBJECTIVE—We sought to determine whether, and if so the mechanism by which, testosterone replacement improves carbohydrate tolerance. RESEARCH DESIGN AND METHODS—Fifty-five elderly men with relative testosterone deficiency ingested a labeled mixed meal and underwent a frequently sampled labeled intravenous glucose tolerance test before and after either placebo or treatment with testosterone patch (5 mg/day) for 2 years. RESULTS—Despite restoring bioavailable testosterone to values observed in young men, the change (24 months minus baseline values) in fasting and postprandial glucose, insulin, and C-peptide concentrations and meal appearance, glucose disposal, and endogenous glucose production were virtually identical to those observed after 2 years of placebo. The change over time in insulin and C-peptide concentrations post–intravenous glucose injection also did not differ. Furthermore, the change over time in insulin action and glucose effectiveness (measured with the unlabeled and labeled “oral” and “intravenous” minimal models), as well as insulin secretion and hepatic insulin clearance (measured with the C-peptide model), did not differ in the testosterone and placebo groups. CONCLUSIONS—We conclude that 2 years of treatment with testosterone in elderly men does not improve carbohydrate tolerance or alter insulin secretion, insulin action, glucose effectiveness, hepatic insulin clearance, or the pattern of postprandial glucose metabolism. Thus, testosterone deficiency is unlikely the cause of the age-associated deterioration in glucose tolerance commonly observed in elderly men.

Background To discover prostate cancer biomarkers, we profiled gene expression in benign and malignant cells laser capture microdissected (LCM) from prostate tissues and metastatic prostatic adenocarcinomas. Here we present methods developed, optimized, and validated to obtain high quality gene expression data. Results RNase inhibitor was included in solutions used to stain frozen tissue sections for LCM, which improved RNA quality significantly. Quantitative PCR assays, requiring minimal amounts of LCM RNA, were developed to determine RNA quality and concentration. SuperScript II™ reverse transcriptase was replaced with SuperScript III™, and SpeedVac concentration was eliminated to optimize linear amplification. The GeneChip® IVT labeling kit was used rather than the Enzo BioArray™ HighYield™ RNA transcript labeling kit since side-by-side comparisons indicated high-end signal saturation with the latter. We obtained 72 μg of labeled complementary RNA on average after linear amplification of about 2 ng of total RNA. Conclusion Unsupervised clustering placed 5/5 normal and 2/2 benign prostatic hyperplasia cases in one group, 5/7 Gleason pattern 3 cases in another group, and the remaining 2/7 pattern 3 cases in a third group with 8/8 Gleason pattern 5 cases and 3/3 metastatic prostatic adenocarcinomas. Differential expression of alpha-methylacyl coenzyme A racemase (AMACR) and hepsin was confirmed using quantitative PCR.

Background: Zn-α2 glycoprotein (ZAG) is a relatively abundant glycoprotein that has potential as a biomarker for prostate cancer. We present a high-flow liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for measuring serum ZAG concentrations by proteolytic cleavage of the protein and quantification of a unique peptide.Methods: We selected the ZAG tryptic peptide 147EIPAWVPEDPAAQITK162 as the intact protein for quantification and used a stable isotope-labeled synthetic peptide with this sequence as an internal standard. Standards using recombinant ZAG in bovine serum albumin, 50 g/L, and a pilot series of patient sera were denatured, reduced, alkylated, and digested with trypsin. The concentration of ZAG was calculated from a dose–response curve of the ratio of the relative abundance of the ZAG tryptic peptide to internal standard.Results: The limit of detection for ZAG in serum was 0.08 mg/L, and the limit of quantification was 0.32 mg/L with a linear dynamic range of 0.32 to 10.2 mg/L. Replicate digests from pooled sera run during a period of 3 consecutive days showed intraassay imprecision (CV) of 5.0% to 6.3% and interassay imprecision of 4.4% to 5.9%. Mean (SD) ZAG was higher in 25 men with prostate cancer [7.59 (2.45) mg/L] than in 20 men with nonmalignant prostate disease [6.21 (1.65) mg/L, P = 0.037] and 6 healthy men [3.65 (0.71) mg/L, P = 0.0007].Conclusions: This LC-MS/MS assay is reproducible and can be used to evaluate the clinical utility of ZAG as a cancer biomarker.

Context.—It is important that the total long-term precision of laboratory methods meet the medical needs of the patients being served.Objectives.—To determine the long-term within- and between-laboratory variation of cortisol, ferritin, thyroxine, free thyroxine, and thyroid-stimulating hormone measurements using commonly available methods and to determine if these variations are within accepted medical needs.Design.—Two vials of pooled frozen serum were mailed 6 months apart to laboratories participating in 2 separate College of American Pathologists surveys. The data from those laboratories that analyzed an analyte in both surveys were used to determine for each method the total variance and the within- and between-laboratory components.Setting.—The study included the A mailing of the 2003 College of American Pathologists Ligand Survey and the C mailing of the Chemistry Survey.Main Outcome Measures.—For each analyte, total variance was partitioned into within- and between-laboratory components for each analytic method. The within-laboratory variations were then compared with imprecision criteria based on biological variation.Participants.—The laboratories that reported results on the same analyte using the same method in both surveys.Results.—For each analyte, the median of the long-term within-laboratory variances of each peer group was 78% to 95% of its total-survey variance, and the median long-term within-laboratory coefficients of variation varied from 5.1% to 7.6%. The number of methods that met within-laboratory imprecision goals based on biological criteria were 5 of 5 for cortisol; 5 of 7 for ferritin; 0 of 7 for thyroxine and free thyroxine; and 8 of 8 for thyroid-stimulating hormone.Conclusions.—For all analytes tested, the total within-laboratory component of variance was the major source of variability in this study. In addition, there are several methods, especially for thyroxine and free thyroxine, that may not meet analytic goals in terms of their imprecision.

Context.—As part of a College of American Pathologists (CAP) proficiency testing survey, a comparison is made between human chorionic gonadotropin (hCG) results from an actual patient pool and a similarly targeted artificial sample. The goal is to gain insight into the possible source(s) of bias attributable to the proficiency testing material (PTM) with a view toward creating more appropriate survey materials.Objective.—To compare hCG and related variants in a pool of fresh frozen sera (FFS) with that found in PTM.Design.—The 2003 CAP K/KN-A Survey included a FFS specimen along with admixtures of PTM. The FFS (K-02) and 1 PTM admixture (K-01) had similar mean hCG values. Five hCG-related analytes were measured on these 2 samples by a reference laboratory.Participants.—Approximately 1800 clinical laboratories and diagnostic test kit manufacturers participated in the K/ KN-A Survey.Main Outcome Measures.—Method imprecision (coefficient of variation) and method bias (relative difference between peer group mean and all-method median) were computed for the 2 samples. Differences were evaluated with respect to hCG-related analytes levels.Results.—All-method hCG results were 12.9 mIU/mL (12.9 IU/L) for the PTM material and 21.6 mIU/mL (21.6 IU/L) for the FFS material. Method biases for 14 manufacturers were greater for PTM than for FFS (−40% to +35% and −16% to +23%). Twelve of 14 methods had higher coefficients of variation on PTM. Total hCG and free β hCG measurements by the reference laboratory were 14.1 mIU/ mL (14.1 IU/L) for the PTM material and 18.5 mIU/mL (18.5 U/L) for the FFS material (FFS), and 2.4 (PTM) and 0.7 (FFS) mIU/mL (2.4 and 0.7 IU/L), respectively. On a molar basis, free β represented 17% and 4% of the total hCG, respectively. Levels of hyperglycosylated hCG, nicked hCG, and β core fragment were not measurable in either sample.Conclusions.—It is unlikely that the hCG added to the PTM is the source of the increased bias and variability. The main difference is a 3-fold increase in free β found in the PTM, but methods previously found to strongly react with free β were not systematically elevated. The biases between manufacturers found for the FFS specimen are likely attributable to calibration differences.

Context.—In proficiency testing surveys, there are differences in the values reported by users of various analytic methods. Two contributors to this variation are calibrator bias and matrix effects of proficiency testing materials. Objectives.—(1) To quantify the biases of the analytic methods used to measure thyroid-stimulating hormone, thyroxine, triiodothyronine, free thyroxine, and free triiodothyronine levels; (2) to determine if these biases are within allowable limits; and (3) to ascertain if proficiency testing materials correctly identify these biases. Design.—A fresh frozen serum specimen was mailed as part of the 2003 College of American Pathologists Ligand and Chemistry surveys. The means and SDs for each analytic method were determined for this sample as well as for a proficiency testing sample from both surveys. In the fresh frozen serum sample, target values for thyroxine and triiodothyronine were determined by isotope dilution/liquid chromatography/tandem mass spectrometry. All other target values in the study were the median of the means obtained for the various analytic methods. Main Outcome Measures.—Calibration biases were calculated by comparing the mean of each analytic method with the appropriate target values. These biases were evaluated against limits based on intra- and interindividual biological variation. Matrix effects of proficiency testing materials were assessed by comparing the rank of highest to lowest analytic method means (Spearman rank test) for each analyte. Participants.—Approximately 3900 clinical laboratories were enrolled in the College of American Pathologists Chemistry and Ligand surveys. Results.—The number of methods in the Ligand Survey that failed to meet the goals for bias was 7 of 17 for thyroid-stimulating hormone and 11 of 13 for free thyroxine. The failure rates were 12 of 16 methods for thyroxine, 8 of 11 for triiodothyronine, and 9 of 11 for free triiodothyronine. The means of the analytic method for the proficiency testing material correlated significantly (P < .05) only with the fresh frozen serum means for thyroxine and thyroid-stimulating hormone in the Chemistry Survey and free triiodothyronine in the Ligand Survey. Conclusions.—A majority of the methods used in thyroid function testing have biases that limit their clinical utility. Traditional proficiency testing materials do not adequately reflect these biases.

The cobalamins, also referred to as vitamin B12, are a group of closely related enzymatic cofactors involved in the conversion of methylmalonyl-coenzyme A to succinyl-coenzyme A and in the synthesis of methionine from homocysteine (1)(2)(3). Vitamin B12 deficiency can lead to megaloblastic anemia and neurologic deficits (4). The latter may exist without anemia or precede it. Adequate replacement therapy will generally improve or cure cobalamin deficiency. Unfortunately, many other conditions, which require different interventions, can mimic the symptoms and signs of vitamin B12 deficiency (4). Moreover, even when cobalamin deficiency has been established, clinical improvement may require different dosages or routes of vitamin B12 replacement, depending on the underlying cause (3)(4). In particular, patients with pernicious anemia, possibly the commonest type of cobalamin deficiency in developed countries, require either massive doses of oral vitamin B12 or parenteral replacement therapy (3)(4)(5). The reason is that in pernicious anemia, patients suffer from gastric mucosal atrophy, which leads to diminished or absent gastric acid, pepsin, and intrinsic factor (IF) production. Because gastric acid, pepsin, and IF are required for liberation of cobalamin from binding proteins and efficient cobalamin absorption in the gut, respectively, vitamin B12 deficiency ensues (3)(4). Most of these patients have autoantibodies against gastric parietal cells or IF, with the latter being very specific but present in only ∼50% of cases (1). The aim of the work-up of patients with suspected vitamin B12 deficiency is therefore to confirm the presence of deficiency and to establish its most likely etiology. Many different testing algorithms have been proposed to achieve maximum sensitivity and specificity for both tasks, but almost all involve measurement of serum vitamin B12 and IF antibodies (IFABs) at …

Eighty-five to 95% of esophageal cancer patients suffer dysphagia. Yet, few studies have focused on this symptom, and four 'myths' persist: (i) dysphagia cannot be measured; (ii) chemotherapy cannot palliate it; (iii) dysphagia predicts a poor prognosis; (iv) dysphagia is associated with a frustratingly insatiable appetite. Forty-four patients with metastatic esophageal cancer participated in this quality of life/translational component of a previously reported clinical trial. All were monitored for chemotherapy efficacy and toxicity and completed questionnaires on dysphagia and appetite at baseline and every 6 weeks. The appetite hormones, leptin and neuropeptide y, were also assessed. Forty-five per cent of patients could easily swallow solid foods; all others had varying dysphagia, thus enabling exploration of these four 'myths.' First, a single-item visual analog scale (Swallowing Scale), demonstrated excellent agreement with a previously validated questionnaire (81% at baseline), thus reminding us that dysphagia is measurable. Second, chemotherapy was associated with a trend towards improved dysphagia (P = 0.059). Third, dysphagia did not predict tumor response or survival. Fourth, dysphagia was not associated with appetite, leptin or neuropeptide y. This study helps to dispel these four 'myths' and underscores the need for further quality of life research on dysphagia.

BACKGROUND Despite biologic plausibility, the associations between sex hormones and measures of benign prostatic hyperplasia (BPH) have not been consistently reported. METHODS Subjects were randomly selected from the Olmsted County, MN population (n, 320; median age, 60.9 years) and followed biennially since 1990. In 2002, surrogate measures of BPH were assessed from an approximation of the American Urological Association Symptom Index (AUASI), Peak urinary flow rates (Qmax), and a transrectal ultrasound assessment of prostate volume. Serum levels of prostate specific antigen (PSA), testosterone, bioavailable testosterone, and estradiol were also measured. RESULTS Bioavailable testosterone levels declined with increasing cross-sectional age from 53.8, 50.2, to 41.2 ng/dl (P = 0.001) in men aged 69 years, respectively, and the estradiol/bioavailable testosterone ratio increased from 0.042, 0.044, to 0.050 (P = 0.04). Among men with bioavailable testosterone above the median, estradiol levels had a dose response relationship with prostate size. Among men with bioavailable testosterone level ≤ the median, however, there was no association between estradiol level and prostate volume CONCLUSIONS While cross-sectional, these findings suggest a more complex relationship between sex steroids and prostate volume in older men than simple independent effects. © 2004 Wiley-Liss, Inc.

Interleukin-1 beta (IL-1beta), tumor necrosis factor alpha (TNFalpha), and interleukin-6 (IL-6) have been implicated in the cancer anorexia/weight loss syndrome. However, previous smaller studies have yielded conflicting results as to whether circulating, serum concentrations of these cytokines are in fact elevated. As the translational component of a large multi-institutional trial, this study assessed the clinical value of serum concentrations of these cytokines in patients with this syndrome.Patients with incurable cancer with anorexia and/or weight loss were eligible. All underwent weekly weight measurements and appetite assessment for the first month and then monthly assessments thereafter. Serum was obtained at baseline and at 1 month, and all three cytokines were measured with the Immunolite assay.A total of 118 patients participated. At baseline, 99%, 54%, and 47% of patients' samples had undetectable IL-1beta, TNFalpha, and IL-6, respectively. Similar results were obtained at 1 month. No correlations were observed between serum cytokine concentrations and changes in weight or appetite. Baseline serum IL-6 predicted a diminished survival but only after adjustment for age and cancer site.Serum concentrations of IL-1beta, TNFalpha, and IL-6, as measured in this study, provide data of limited clinical value for patients with the cancer anorexia/weight loss syndrome.

Despite the numerous potential interferences that were discussed in this article, immunoassays, in general, are robust measurement systems. There is no practical way to identify specimens a priori that are likely to have immunoassay interference. Therefore, laboratories must rely on communication from clinicians to identify suspicious test values that may be caused by assay interference. After laboratories are alerted, multiple investigations can be undertaken. The common causes of immunoassay interferences (see Box I) are dependent on the analytic format. Competitive assays are most likely to have problems with cross-reactivity, whereas immunometric assays most often have problems with heterophile antibodies. The simple steps to test for dilutional linearity, spiked recovery, heterophile antibody blocking,and testing with alternate technology can help in the evaluations of cases that are suspected to have assay interference.

Assays are now available that can measure very low concentrations of prostate-specific antigen (PSA), but their analytic performance and clinical utility are not well defined. This brief article highlights some of the clinical issues related to the limited prognostic significance of small changes in PSA concentrations in men with prostate cancer who have been treated with prostate ablation therapy. College of American Pathologists proficiency survey data are presented, illustrating the performance of commercial PSA assays with low PSA concentration survey samples tested between 1998 and 2002. The performance of the assays appears to be improving, but many of the currently used assays have intralaboratory coefficients of variation greater than 20% for PSA concentrations less than 0.4 ng/mL. Also, there are major differences in the level of PSA reported by various assays in these low concentration samples. These level differences (if they are also seen in clinical samples) may cause clinical problems when fixed serum PSA thresholds (eg, 0.2 ng/mL) are used to make clinical decisions related to prostate tumor recurrence.

Lipoprotein(a) (Lp(a)) is a potential risk factor for coronary artery disease (CAD). The relationship between serum Lp(a) and coronary artery calcification (CAC), a measure of subclinical coronary artery atherosclerosis, has not been extensively explored.Electron beam computed tomography was performed on 616 asymptomatic, white individuals (285 men) from a community-based study. Mean age was 57.2 years. Serum Lp(a) levels were measured by an immunoturbidimetric assay. Tobit regression was used to determine the sex-specific association of Lp(a) levels with presence and quantity of CAC.In women, Lp(a) was a significant predictor (P=0.0426) of presence and quantity of CAC after adjustment for age, hypertension status, waist circumference, presence of high low-density lipoprotein cholesterol (LDL-C), and history of smoking. In men, after adjusting for age, hypertension status, body mass index, presence of high LDL-C, and history of smoking, a positive interaction between Lp(a) and history of smoking (P=0.0387) was significantly associated with presence and quantity of CAC.Sex-specific relationships between Lp(a) and CAC provide evidence supporting sex-specific risk factor profiling for CAD. In women, Lp(a) alone may be an independent risk factor for coronary atherosclerosis, while in men, Lp(a) may confer higher risk conditional on the presence and level of other risk factors. The role of Lp(a) in the prediction and pathogenesis of subclinical coronary atherosclerosis needs to be further elucidated.

A major dilemma associated with immuno(metric) assays for biomarkers is that various kits employing antibodies with differing specificities and binding affinities may generate non-equivalent test results. Also, variation in sample processing and the use of different standards (reference material) may result in discordant test results. Therefore, assays and procedures should be standardized and the quality of biomarker assay results should be monitored by continuous between-laboratory proficiency testing of performance. External quality control requires an established network of expert laboratories in which the investigators interact freely and where technical issues are discussed. Although such networking is more often praised than practiced, we strongly endorse and advocate between-laboratory exchange of experience and information. The present study discusses analytical aspects of immuno(metric) biomarker assays and presents recommendations of the Receptor and Biomarker Group of the EORTC (European Organisation for Research and Treatment of Cancer) how such tests should be validated for first time and day to day use. Moreover, a model for an appropriate quality assurance program is presented.

Cytokines play an important role in the immune response to live measles virus immunization. To gain further insight into the cytokine production profile in response to measles vaccination, we studied interferon-gamma (IFN-gamma), tumor necrosis factor (TNF-alpha), soluble IL-2 receptor (sIL-2R), interleukin-2 (IL-2), interleukin-4 (IL-4), and interleukin-6 (IL-6) in both supernatants from peripheral blood mononuclear cells (PBMC) stimulated with phytohaemagglutinin (PHA), and plasma. We enrolled 57 healthy infants and children residing in an area where no measles virus circulated in their lifetimes. Overall analysis of cytokines in supernatants from PBMC showed that a predominant Th1 cytokine pattern occurs after the second dose of measles immunization. However, plasma levels of Th1 cytokines (IFN-gamma, sIL-2R and TNF-alpha) were preferentially activated by measles virus after the first dose of measles vaccination. Median IFN-gamma plasma levels were 1.73 pg/ml for infants compared to 0.63 pg/ml for older children (P = 0.003). These data suggest that after the first and the second dose of measles virus immunization, there is a predominant Th1-type directed immune response, but the Th1 cytokine pattern seems to be stronger in previously unvaccinated children. There was no correlation between cytokine production by PBMC supernatants after PHA stimulation and circulating levels of plasma cytokines. No relationship was found between any specific cytokine level and measles antibody level.

Glucose tolerance decreases with age. For determining the cause of this decrease, 67 elderly and 21 young (70.1 +/- 0.7 vs. 23.7 +/- 0.8 years) participants ingested a mixed meal and received an intravenous injection of glucose. Fasting glucose and the glycemic response above basal were higher in the elderly than in the young participants after either meal ingestion (P0.001) or glucose injection (P0.01). Insulin action (Si), measured with the meal and intravenous glucose tolerance test models, was highly correlated (r = 0.72; P0.001) and lower (Por= 0.002) in the elderly than in the young participants. However, when adjusted for differences in percentage body fat and visceral fat, Si no longer differed between groups. When considered in light of the degree of insulin resistance, all indexes of insulin secretion were lower (P0.01) in the elderly participants, indicating impaired beta-cell function. Hepatic insulin clearance was increased (P0.002), whereas total insulin clearance was decreased (P0.002) in the elderly subjects. Multivariate analysis (r = 0.70; P0.001) indicated that indexes of insulin action (Si) and secretion (Phi(total)) but not age, peak oxygen uptake, fasting glucose, degree of fatness, or hepatic insulin clearance predicted the postprandial glycemic response. We conclude that the deterioration in glucose tolerance that occurs in healthy elderly subjects is due to a decrease in both insulin secretion and action with the severity of the defect in insulin action being explained by the degree of fatness rather than age per se.

Laboratory studies suggest that insulin-like growth factor I (IGF-I) promotes prostatic growth. The authors evaluated the association between benign prostatic hyperplasia and IGF-I and its binding protein IGFBP-3 in community-dwelling men to determine whether this laboratory finding is manifest at the population level. Participants (n = 471) were Olmsted County, Minnesota, Caucasian males aged 40–79 years in 1990. Urologic measures were assessed from the International Prostate Symptom Score, peak urinary flow rates, prostate volume, and serum prostate-specific antigen (PSA), and serum IGF-I and IGFBP-3 levels were measured. After adjustment for age, the relative odds (odds ratios) of an abnormal urologic measure in men with high versus low serum IGF-I levels were 0.98 (95% confidence interval (CI): 0.66, 1.45) for a symptom score of >7, 1.14 (95% CI: 0.72, 1.80) for a peak urinary flow rate of 30 ml, and 0.71 (95% CI: 0.46, 1.09) for a PSA level of >1.4 ng/ml. A low IGFBP-3 level was associated with an enlarged prostate (odds ratio = 1.72, 95% CI: 1.05, 2.82), after simultaneous adjustment for IGF-I and age, but not with other urologic measures. These data do not provide evidence for an association between benign prostatic hyperplasia and serum IGF-I. insulin-like growth factor binding protein 3; insulin-like growth factor I; men; prostate-specific antigen; prostatic hyperplasia; urological manifestations

The spun packed cell volume (PCV, hematocrit) is a key measurement on which are based hematology instrument calibration, reference range determination, and assignment of values to calibrators/controls. In 2001, the International Council for Standardization in Haematology (ICSH) recommended a Reference PCV method, which is fully traceable to the ICSH reference hemoglobin method. Because of its complexity, however, this method is impractical for occasional use in routine laboratories and is therefore intended primarily for use by manufacturers of capillary microhematocrit tubes, liquid calibrators, and multichannel analyzers. In response to the need for a simpler method--accessible to all routine laboratories--the ICSH offers this "Surrogate Reference" PCV procedure. It is traceable to the original ICSH Reference PCV method and is based on spun PCVs obtained using borosilicate capillary tubes with an already-known relationship to this reference procedure. This ICSH "Surrogate Reference" PCV method is substantially simpler, thus putting it within the reach of most routine hematology laboratories.

Homocysteine is associated with coronary disease (CAD). However, the strength of the association after accounting for traditional and emerging risk factors is unclear, particularly since flour fortification with folate was mandated in the USA. We analyzed the association between traditional and emerging risk factors and CAD in 504 patients undergoing clinically-indicated angiography between July 1998 and January 1999. Significant CAD (or =50% stenosis inor =1 artery) was present in 271 patients (54%). Mean homocysteine (micromol/l) was 9.36+/-3.07; hyperhomocysteinemia (13 micromol/l) was present in 7.9% of patients. Mean homocysteine was 9.29+/-3.02 in patients with no disease (no stenoses or stenoses10%), 9.09+/-2.47 in patients with mild disease (stenoses 10-50%), 9.12+/-2.39 in patients with one vessel disease (VD) (50% stenosis in one coronary artery), 9.28+/-3.19 in patients with two VD, and 10.1+/-3.89 in patients with three VD (P=0.0793). Multivariate analysis that included age, gender, smoking, LDL, HDL, Lp(a), apo A1, and apo B revealed no independent association between quartile of homocysteine and odds ratio (OR) for CAD. In summary, we found no association between homocysteine and CAD on angiography. The homocysteine-lowering effect of folate-fortified flour, or the inclusion of many traditional and emerging risk factors in multivariate analysis, are potential explanations.

Reine de Tendre ou souveraine des Précieuses, « institutrice des mœurs » d’après Sainte-Beuve ou nouvel « oracle de la galanterie », comme le lui écrivait en 1654 son ami Antoine Godeau, l’évêque de Grasse, l’« illustre Sapho » - autre avatar de Madeleine de Scudéry - a suscité dès l’origine les qualifications les plus diverses. Mêlée aux premières satires des Précieuses, exemplaire dans ses stratégies de résistance à cette entreprise polémique, fondatrice enfin, pour ses contemporains, d’une lignée moderne de femmes de lettres à qui elle aura ouvert, non sans difficultés, le chemin de l’écriture, la romancière occupe désormais dans l’histoire littéraire une place que nul ne songe plus à lui contester. Même si cette place reste, précisément, à mieux situer dans des territoires dont les contours sont en pleine redéfinition, à l’heure où les catégories majeures (classicisme, baroque, préciosité, galanterie) se voient aujourd’hui l’objet d’un salutaire réexamen. L’œuvre elle-même, dans sa richesse et sa diversité, s’ouvre enfin aux lectures savantes, après avoir été longtemps occultée par la figure presque mythique de sa créatrice - la « griffonneuse Sapho », selon le mot cruel de Chapelain -, et trop souvent traitée comme simple document pour une lecture pseudo-historique de la société française au xviie siècle, de ses usages mondains et de ses figures légendaires. C’est dire qu’il était temps de consacrer à Madeleine de Scudéry un colloque dont l’occasion (la célébration du tricentenaire de sa mort) offrait un prétexte à l’urgence. Dix ans tout juste après le colloque du Havre consacré aux Trois Scudéry, le moment paraissait venu d’offrir à la seule Madeleine une première moisson d’essais critiques, susceptibles d’interroger les divers aspects de son œuvre, d’en apprécier la portée, d’en évaluer les lectures.

To the Editor: Cardiac troponin is the marker of choice for evaluating myocardial injury (1). High-sensitivity assays improve analytical detection limits, thereby allowing concentrations to be measured in the majority of healthy individuals. This capability allows an assessment of biologic variation (BV)1 to determine what constitutes a clinically important change in the cardiac troponin concentration, a critical metric for identifying acute events. Such an event is often a myocardial infarction, but any acute cardiac injury can cause increasing and/or decreasing values (1). Accordingly, we evaluated BV for a recently developed high-sensitivity cardiac troponin I (hs-cTnI) assay (2) from Beckman Coulter. We performed this study with the same cohort used to define BV for the high-sensitivity cardiac troponin T (hs-cTnT) assay (3) and according to a protocol approved by our institutional review board. For assessment of short-term BV, we collected blood into serum separator tubes (Becton Dickinson) at 0, 1, 2, 3, and 4 h, centrifuged the tubes, and stored the serum samples immediately at −70 °C. …

Anorexia is a noxious symptom, and over half of patients with advanced cancer experience it. Neuropeptide Y (NPY), leptin, and cholecystokinin 8 (CCK8) have been implicated.This exploratory study 1) compared circulating concentrations of NPY and leptin between anorectic cancer patients and historic controls and 2) explored whether NPY, leptin, or CCK8 may serve as correlates of anorexia severity. Cancer patients met predefined eligibility criteria: 1) weight lossor = 2.3 kg over the preceding 2 months and/or a physician-estimated caloric intake of20 calories per kilogram of body weight per day and 2) patient acknowledgment that appetite or weight loss was an ongoing problem.Seventy-three cancer patients were studied, and90% reported aor = 50% decline in appetite from baseline in the preceding 2 months. NPY levels were lower than control values: mean +/- standard deviation, 466 pg/mL +/- 161 pg/mL versus 560 pg/mL +/- 151 pg/mL, respectively (P = 0.004). Because a few (but not all) earlier studies suggested an age-related decline in NPY levels, a subgroup analysis was performed and found no age-adjusted difference in NPY levels between groups. Similarly, leptin concentrations were not different between groups. Significant correlations were not observed between anorexia severity and NPY, leptin, or CCK8 levels.There were no differences in leptin and CCK8 levels between anorectic cancer patients and historic controls. Circulating concentrations of NPY, leptin, and CCK8 did not correlate with anorexia severity. However, the current results suggest a need for further examination of NPY in cancer-associated anorexia.

Human kallikrein 2 (hK2) shares 80% sequence identity with prostate-specific antigen (PSA). Because both hK2 and hK2-alpha(1)-antichymotrypsin (hK2-ACT) complexes have been identified in patient sera, we devised an immunoassay for total hK2 [(thK2); hK2 and hK2-ACT] and evaluated it in healthy subjects and patients with prostate disease.We developed monoclonal antibodies (mAbs) with high specificity for hK2 and hK2-ACT and minimal cross-reactivity to PSA. Using these mAbs, a sandwich assay was developed and its specificity for forms of hK2 was assessed. Serum samples (n = 1035) from healthy volunteers, patients with increased PSA, and men who had undergone radical prostatectomy were assayed for thK2. We also measured thK2 in samples before and after storage under common laboratory conditions.The minimum detectable concentration in the thK2 assay was 0.008 microg/L, and PSA cross-reactivity was0.001%. The assay detected prohK2 and three different hK2-serum protease complexes. The median serum concentration of thK2 in control samples (0.013 microg/L) was significantly lower than the median in samples from patients with increased PSA concentrations (0.085 microg/L). Immunoreactive hK2 changed little in samples stored for up to 1 month at -70 degrees C.The thK2 assay recognizes all forms of hK2 that have been found in bodily fluids to date.

Originating from the pituitary gland, TSH secretion is regulated predominantly by thyroid-releasing hormone (TRH) neurons located in the hypothalamus. Norepinephrine and dopamine have important effects in modulation of TSH secretion. An inhibitor of catecholamine synthesis, alpha-methyl-para-tyrosine (AMPT) has been used in several studies of the regulation of human TSH secretion. The short-term effects (8 hours) of low doses of AMPT include stimulation of pituitary TSH secretion by selective lowering of brain dopamine levels. After prolonged administration of AMPT (24 hours), theoretically both dopamine and norepinephrine levels are lowered significantly in the brain, although this has not been reported previously.Nine subjects (five women and four men) received a total of five 1-g doses of AMPT or five 50-mg doses of promethazine (active placebo) over 28 hours in a randomized, double-blind, placebo-controlled crossover design in which the active and control tests were separated by 4-6 weeks. Blood samples were obtained over 24 hours (18 time points) on day 2 of each condition.Changes in prolactin secretion and 6-hydroxymelatonin sulfate excretion indirectly showed the effects of AMPT on dopamine and norepinephrine. The typical circadian rhythm of TSH secretion was blunted by AMPT throughout the night; at ten time points, the difference between the two groups was statistically significant (P.01). The long-term effects of repeated doses of AMPT were inhibition of TSH secretion and significant attenuation of the circadian rhythm of TSH. Additionally, AMPT induced low norepinephrine levels, which counteracted the stimulatory effect of low dopamine levels on TSH.Through its inhibitory effect on TRH, norepinephrine appeared to be involved in the regulation of TSH.

To determine if the levels of imprecision of the commonly used analytic methods for drug measurements are suitable for long-term therapeutic drug monitoring.In 1996, 4 identical lyophilized samples (2 in the first mailing and 2 in the second mailing 4 months later) were sent to laboratories participating in a nationwide proficiency testing program. Similarly, in 1999, replicates from a liquid pool of spiked sera were mailed 3 times, 4 months apart, to participating laboratories. For each of 11 drugs regulated under the Clinical Laboratory Improvement Amendments of 1988 and 1 metabolite, the total variance for each method was partitioned into within- and between-laboratory components. The total within-laboratory and the total survey coefficients of variation (CVs) for each method were then compared with the "acceptable" precision criteria of Glick, Burnett, and Fraser for each drug.The first 2 mailings of the College of American Pathologists Therapeutic Drug Monitoring surveys for 1996, sets Z and ZM, and the 3 mailings of 1999, sets ZM, Z, and Z2.For each drug studied, the CV of each method was compared with the various imprecision criteria, and if greater than any of the criteria, the method was then tabulated as not meeting that specific criterion.Participants.-The approximately 5000 participants of the survey.The number of methods deemed as not having acceptable total long-term within-laboratory precision by the various criteria ranged from 35% to 88% in 1996 and from 22% to 77% in 1999.The number of failures possibly indicates that many of the reagent assays being utilized are not precise enough for long-term therapeutic drug monitoring of chronically administered drugs or that the published criteria used to evaluate the data in this study are too stringent.

To determine the magnitudes and sources of analytic variation in testing for therapeutic drugs. Specifically, among laboratories using the same analytic method, to compare the within-laboratory variation (including both short- and long-term variation) with the between-laboratory variation.Four identical challenges were prepared from a lyophilized pool of spiked sera and were sent in pairs 4 months apart to laboratories participating in a nationwide proficiency-testing program. For each of 25 drugs, the variability in reported results from laboratories using the same method was investigated using nested analysis of variance.The first 2 mailings of the College of American Pathologists Therapeutic Drug Monitoring Survey, 1996, sets Z and ZM.For each drug, total variance was partitioned into within- and between-laboratory components for common methods. The within-laboratory component was further partitioned into short- and long-term components.The approximately 5000 laboratories enrolled in the survey.For the 25 drugs, the average percentages of the total variance due to short-term, within-laboratory variance; long-term, within-laboratory variance; between-laboratory variance; and total laboratory variance were 25.0% (range, 8.8--50.6%), 57.8% (35.3--73.7%), 17.3% (5.0--35.4%), and 82.7% (64.6--95.0%), respectively.For all drugs tested, the within-laboratory component of variance was greater than the between-laboratory component of variance. Within laboratories, the magnitude of the long-term component was generally greater than the magnitude of the short-term component. This information will be helpful in determining the clinical utility of various drug assays and in evaluating the appropriateness of regulations involving therapeutic drug testing.

This issue of Clinical Chemistry contains 3 reports from the IFCC Working Group for Standardization of Thyroid Function Tests. The first report relates to thyroid-stimulating hormone (TSH)1 (1), the second addresses free thyroxine (FT4) and free triiodothyronine (FT3) (2), and the third discusses total thyroxine (T4) and total triiodothyronine (T3) (3). Each of these reports is authored by a group of experts who relate not only their own experience but also the experience of various professional organizations. This broad representation is important for the potential harmonization role that the authors hope to promote with these reports. The chair of this group, Linda Thienpont, was also project leader for the measurements of the total and free thyroid hormones in the prior groundwork project initiated by the European Commission, “Feasibility Studies for the Development of Reference Measurement Systems for Thyrotropin (TSH) and for Free Thyroxine (FT4), and Validation of Reference Measurement Systems (Procedure and Material) for Thyroxine (T4) and Triiodothyronine (T3) in Human Serum (2001–2005)” (4). This working group also included Catherine Ronin (Laboratories de Neurobiologic, Marseille, France), who was the project leader for the TSH measurements in this European Commission project. International leaders in standardization from both academia and industry participated in this undertaking. The major goal for standardization of thyroid function tests is the harmonization of patient test results. Standardization and harmonization are 2 separate but closely …

Large disparities in prostate-specific antigen (PSA) results from different assays have been observed in the College of American Pathologists (CAP) Ligand Assay Survey, with interassay results varying severalfold. Survey specimens are predominately composed of free PSA and do not reflect the composition of typical patient specimens.To characterize a pilot material developed for CAP in which pooled sera samples were spiked with purified PSA and alpha(1)-antichymotrypsin-bound PSA at targeted concentrations and to compare it to CAP survey and reference materials.CAP survey, reference, and pilot materials were analyzed using 10 total PSA and 7 free PSA assays. These assays included Food and Drug Administration-approved assays and assays for research use only.Variability among the 10 total PSA methods was greatest for the 1997 ligand survey material (CV range, 56%-65%) followed by the pilot material (CV range, 10%-29%) and the reference material (CV range, 6%-13%). In contrast, interassay variability for the 7 free PSA methods was similar for the 3 preparations, with the exception of one specimen close to the limit of detection of the assays. As determined with the Hybritech Tandem-R method, the ligand survey specimens were essentially composed of all free PSA, whereas the reference and pilot materials were composed of approximately 10% and 35% free PSA, respectively.The newly formulated pilot material prepared using a human base that contained defined concentrations of free PSA and alpha(1)-antichymotrypsin-bound PSA more closely resembled patient specimens and minimized differences among methods compared with the semen-supplemented original survey material.

Abstract —Increased plasma fibrinogen concentration is an independent risk factor for cardiovascular disease. Fibrinogen is the main coagulation protein in plasma, a determinant of blood viscosity, and can act as a cofactor for platelet aggregation. In this study of middle-aged men and women, we examined the association between plasma fibrinogen concentration and coronary artery calcification (CAC), a marker of preclinical coronary atherosclerosis. Two hundred twenty-eight participants were selected from the community-based Epidemiology of Coronary Artery Calcification Study, in which CAC was measured noninvasively by electron beam computed tomography. One hundred fourteen participants (57 men) were selected because they had high quantities of CAC; the remaining 114 participants (57 men) were selected because they had no detectable CAC. Logistic regression models were used to investigate the association between plasma fibrinogen concentration and high quantity of CAC. In men, an increase of 1 standard deviation in fibrinogen concentration was associated with a statistically significant odds ratio of 1.6 (95% CI 1.1 to 2.5) for a high quantity of CAC. In women, the corresponding odds ratio was 2.5 (95% CI 1.6 to 4.1). Inferences from sex-specific bivariate logistic models for odds ratios adjusted individually for each coronary risk factor and C-reactive protein were similar to those from the univariate models. In women, there was also a significant interaction between fibrinogen concentration and age. According to the models, younger women with high plasma fibrinogen were more likely to have high quantities of CAC than were younger women with low plasma fibrinogen. The strength of this association was diminished in older women.

In today's clinical and research settings, there is an unfortunate lack of consistency for the term "measuring testosterone status." This term is often used to refer to a measure of biologic androgen activity rather than the specific measurement of the chemical concentration of the testosterone steroid molecule. Even the measurements of chemical concentrations show considerable methodologic differences. This is true for measurements in elderly men, as well as in other populations, including women. All of the current methods for measuring total testosterone have limitations, especially with regard to low concentrations. In addition, unresolved questions concerning the active form of the hormone preclude definitive determination of which form of testosterone and which other androgen hormones are best suited for measuring androgen activity. When measurement techniques are compared, the numbers correlate with each other but certainly do not represent the same value. There is a need for a consensus as to which forms of hormones should be measured to best assess androgen status, and there is a need to standardize the procedures used to measure these hormones.

Human anti-mouse antibodies (HAMA) are human immunoglobulins with specificity for mouse immunoglobulins. This topic currently is of interest because of the increased use of monoclonal mouse antibodies as diagnostic reagents both for in vitro laboratory measurements and for in vivo imaging studies. Monoclonal mouse antibodies also are being used therapeutically. This short article reviews the production of HAMA in patients receiving monoclonal antibodies and illustrates the potential ways that HAMA can interfere with immunoassay measurements. Methods for measuring and neutralizing HAMA also are discussed.

Colorectal tumor-associated antigens are attractive targets for novel stool-screening assays. MUC1, a glycoprotein antigen, is aberrantly expressed in transformed colorectal mucosa and represents a candidate fecal biomarker. In this study, tissue staining and stool testing were performed to further clarify the discriminant potential of MUC1 in markedly different biologic media. One anti-MUC1 monoclonal antibody (MA5) was used for immunohistochemistry and two commercially available MUC1 assay kits (ELSA-CA 15-3 and Truquant BR) were used for stool detection. On tissue staining, MUC1 expression was strong in 40/40 (100%) adenocarcinomas, moderate in 42/55 (76%) adenomas, faint in 8/28 (29%) juxtatumoral mucosa specimens, and absent in 15/15 (0%) nonadjacent mucosa specimens. Conversely MUC1 levels in stool testing did not differ between colorectal cancer cases (N = 14) and controls (N = 14). Based on these results, MUC1 appears to be a functional tumor biomarker in colorectal tissue but not in stool. Bacterial metabolism within stool may unmask the core antigen of MUC1 and account for this discordance in immunoreactivity.

The level of serum neuron-specific enolase (NSE) has been implicated as a prognostic factor for patients with small cell lung cancer (SCLC). A prospective evaluation was undertaken to assess the prognostic significance of pretreatment NSE and treatment-induced minimum NSE values in patients with SCLC. Patients from two Phase III North Central Cancer Treatment Group trials [one for patients with extensive stage SCLC and one for patients with limited stage SCLC] were asked to enter this laboratory correlational trial. Both trials included treatment with four to six cycles of etoposide and cisplatin, and 121 patients (71 extensive stage SCLC and 50 limited stage SCLC) were entered into the present study of NSE. Pretreatment NSE values and treatment-induced minimum NSE values were independent predictors of time to progression and survival in multivariate analysis. Hazard rate modeling allowed the formulation of specific relationships of NSE to time to progression and survival. Pretreatment NSE levels inversely correlated with time to progression and survival in these patients with SCLC. Pretreatment NSE accounted for 28% of the variance in survival. Both pretreatment NSE and treatment-induced minimum NSE were independent prognostic predictors of time to progression and survival.

The diagnosis of cholangiocarcinoma is often difficult, making management approaches problematic. A reliable serum tumor marker for cholangiocarcinoma would be a useful additional diagnostic test. Previous studies have demonstrated that elevated serum concentrations of CA 19-9, a tumor-associated antigen, have good sensitivity and specificity for cholangiocarcinoma in patients with primary sclerosing cholangitis. However, the value of this tumor marker for cholangiocarcinoma unassociated with primary sclerosing cholangitis is unclear. Thus, the aims of this study were to determine the usefulness of a serum CA 19-9 determination in the diagnosis of de novo cholangiocarcinoma.We prospectively measured serum CA 19-9 concentrations in patients with cholangiocarcinoma (n = 36), nonmalignant liver disease (n = 41), and benign bile duct strictures (n = 26). Serum CA 19-9 concentrations were measured by an immunoradiometric assay (CIS Bio International) without knowledge of the clinical diagnosis.The sensitivity of a CA 19-9 value100 U/ml in diagnosing cholangiocarcinoma was 53%. When compared with the nonmalignant liver disease and the benign bile duct stricture groups, the true negative rates were 76% and 92%, respectively. Patients with unresectable cholangiocarcinoma had significantly greater mean CA 19-9 concentrations compared to patients with resectable cholangiocarcinoma.These data suggest that the serum CA 19-9 determination is a useful addition to the available tests for the differential diagnosis of cholangiocarcinoma.

In this month’s issue of Clinical Chemistry , Anborgh et al. demonstrate that differences in assay configuration can produce major differences in the association of plasma osteopontin measurements with survival in prostate cancer (1). Prediction of survival was found to be significantly better with assays that have a monoclonal antibody targeted to a specific epitope on the osteopontin molecule. This linkage between assay configuration and clinical utility may have major implications on the way reference materials and reference methods are formulated, because, as this report shows, the reference standards may need to focus on specific forms of the analyte. Various national and international organizations are working to develop reference standards to help harmonize diagnostic assays. The European Union In Vitro Diagnostics Directive (98/79/EC) requires manufacturers marketing in the European Union to provide evidence that the values assigned to calibrators and control materials are traceable, through available reference measurement procedures and reference materials (when available), to standards of a higher metrological order (2)(3). The Joint Committee on Traceability in Laboratory Medicine (JCTLM)1 has helped guide the logistics of traceability with the use of European Committee for Standardization (CEN) and International Organization for Standardization (ISO) standards (4). ISO document 17511 distinguishes 2 broad categories of measurands: type A analytes, which are traceable to International System (SI) units, and type …

The efficacy of endocrine tests depends on the choice of tests, the preparation of the patients, the integrity of the specimens, the quality of the measurements, and the validity of the reference data. Close dialogue among the clinicians, the laboratory, and the patients is a key factor for optimal patient care. The characteristics of urine and plasma samples and the advantages and limitations of paired test measurements are presented. The importance of test sequence strategies, provocative or inhibitory procedures, and elimination of drug interferences is illustrated with four cases involving Cushing syndrome, pheochromocytoma, primary aldosteronism, and hypercalcemia. For each of these scenarios, key clinical issues are highlighted, along with discussions of the best test strategies, including which medications are likely to interfere. The importance of targeting laboratory tests to answer well-focused clinical decisions is emphasized. The roles of some time-honored provocative procedures are questioned in light of more sensitive and specific analytic methods. The importance of decision-focused analytical tolerance limits is emphasized by demonstrating the impact of analytic bias on downstream medical resource utilization. User-friendly support systems to facilitate the implementation of test strategies and postanalytic tracking of patient outcomes are presented as essential requirements for quality medical practice.

T3 plays an important role in the regulation of cell growth and differentiation. In this study, we show the interactive effects of T3 and androgens on the growth response and expression of the prostate-specific genes, PSA (prostate-specific antigen) and hK2 (human glandular kallikrein), in the human prostate cancer cell line, LNCaP. T3 alone showed pronounced growth enhancement in a dose-dependent fashion. However, in the presence of androgens, higher concentrations of T3 were required to produce additional proliferative effects. T3, androgens, or a combination of the two up-regulated PSA protein production in a dose-dependent fashion, but T3 had little stimulatory effect on hK2 protein expression, regardless of the presence or absence of androgens. Using gene transfer assays, T3 alone showed no effect on transcriptional activation of a reporter gene mediated by the PSA or hK2 enhancer/promoters. T3 potentiated the androgen-mediated transcription of the PSA gene but not that of the hK2 gene. A previous study suggested that the T3 effect on PSA protein expression was caused by an up-regulation of the androgen receptor (AR) protein by T3. Our results contradict these. Although AR expression was increased by T3 alone, Western blot analysis showed that the total cellular AR level was not further increased by T3 in the presence of androgens, in comparison with cells stimulated by androgens alone. Both Western blot analysis and a gel DNA band shift assay revealed that nuclear AR was not increased by T3. This study suggests that transcription factor(s) other than the AR may mediate T3 enhancement of androgenic induction of PSA expression.

Because it is a competitive inhibitor of tyrosine hydroxylase, alpha-methyl-para-tyrosine (AMPT) is used to study psychiatric disorders. Melatonin serves as a biological marker of catecholamine function since its secretion is regulated by noradrenergic neurons via beta-adrenergic receptors in the pineal gland. Ten healthy volunteers were administered AMPT in a double-blind placebo controlled study. When subjects received AMPT, nocturnal 6-hydroxymelatonin sulfate (6-SM) decreased significantly as compared with promethazine (night 1 P=0.002; and night 2 P=0.001). Urinary MHPG also decreased on both study days (DF1,9 F=9.82, GG=0.0121). Nocturnal 6-SM excretion and melatonin secretion correlated highly (r=0.91, P=0.0007). Behavioral ratings did not reveal a difference in symptomatology and did not correlate with changes in 6-SM or MHPG. This study demonstrates in healthy controls that 6-SM reliably reflects presynaptic catecholamine depletion induced by AMPT without the emergence of behavioral symptoms.