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Background: Sample collection site may affect the dynamics of intraoperative parathyroid hormone monitoring (IPM) and influence surgical decisions., Methods: We prospectively studied 45 patients undergoing parathyroidectomy for primary hyperparathyroidism. The IPM cure criterion was a decrease in peripheral vein (PV) parathyroid hormone (PTH) of >50% at 10 minutes after gland excision. PTH samples were collected simultaneously from PV and central vein (CV) and compared for PTH decay, the incidence of >50% PTH decay, and the incidence of normal PTH values after gland excision., Results: Mean PTH levels were significantly higher from the CV before and after gland excision. Mean PTH decay 10 minutes after gland excision was 89% PV versus 88% CV, resulting in mean PTH levels of 27 +/- 23 and 39 +/- 35 pg/mL, respectively (P < .0001). At 5 minutes, >50% decay in PTH was present in 98% PV versus 88% CV samples. By 10 minutes, the incidence of >50% PTH decay was equivalent (98%). This yielded normal range PTH levels from the PV versus CV in 90% versus 76% of patients at 5 minutes, 96% versus 89% at 10 minutes, and 95% versus 81% at 20 minutes. Of 45 patients, 44 (98%) are normocalcemic at a mean follow-up of 6.3 months. IPM predicted the single operative failure., Conclusions: CV sampling produces significantly higher PTH levels. Surgeons sampling from a PV may observe a >50% decrease in PTH and normal range PTH values starting 5 minutes after gland excision. Surgeons who sample from the CV and require normalization of PTH levels may have to wait longer and/or continue potentially unnecessary neck exploration.

Background: Intraoperative parathyroid hormone (IOPTH) monitoring in parathyroidectomy for multigland disease is less clear than for single-gland disease. This study assesses the role of IOPTH for hyperplasia., Methods: A prospective database revealed 45 patients with hyperplasia undergoing parathyroidectomy utilizing IOPTH from February 1999 to August 2003., Results: Twenty-six females and 19 males had a mean age of 55 years. Twenty-two patients underwent total parathyroidectomy. Twenty-three patients underwent subtotal parathyroidectomy. Twenty-seven patients (60%) had a drop of IOPTH greater than 50% at 10 minutes after removal of all presumably abnormal parathyroid tissue. Nine additional patients (20%) had an IOPTH drop greater than 50%, but continued exploration revealed more abnormal tissue. Nine patients failed to decrease greater than 50%, and exploration was continued. A final IOPTH less than 35 pg/mL or a greater than 90% decrease from baseline was predictive of a successful operation in 40 patients. The 5 patients who did not meet this criteria remained hyperparathyroid., Conclusions: IOPTH identifies sporadic hyperplasia and guides completeness of resection for patients with known hyperplasia. However, more rigid criteria are required than for adenomas. Failure to achieve appropriate decreases in IOPTH should prompt further neck exploration or a search for a mediastinal gland.

Background: Intraoperative intact parathyroid hormone (iPTH) monitoring is useful in the operative management of hyperparathyroidism. Recent studies suggest that measurement of intraoperative total serum calcium (TSC) levels may be a more cost effective and readily available method of intraoperative guidance during neck dissection than iPTH levels, the gold standard. We compared the accuracy of intraoperative TSC to iPTH in predicting surgical cure during parathyroidectomy., Patients and Methods: From September 1, 2001 to October 31, 2002, 88 parathyroidectomies were performed. iPTH and TSC were measured at the start of the operation, and at 5 and 10 min after gland removal. Data were compared, and trends were analyzed with respect to removal of abnormal parathyroid tissue as confirmed by pathology. One-way analysis of variance was used to determine if decreases in TSC were significant., Results: The mean baseline iPTH level (418 +/- 610 pg/ml) dropped by 70% 5 min after removal of the abnormal glands (86 +/- 102 pg/ml) and by 85% at 10 min (39 +/- 39 pg/ml). The mean baseline TSC level (10.0 +/- 0.8 mg/dl) dropped by 4% at 5 min after removal of the abnormal glands (9.6 +/- 0.9 mg/dl) and remained at 4% at 10 min (9.6 +/- 0.8 mg/dl). iPTH dropped by > or =50% in 73 patients (83%) at 5 min and in 87 patients (99%) at 10 min after gland resection. TSC decreased below baseline at 5 min and remained below baseline at 10 min in only 47 patients (54%). In the remaining patients, intraoperative TSC changes were less predictable and did not respond consistently to resection of abnormal glands., Conclusions: The decreases in TSC during parathyroidectomy, if present, are minimal. Unlike iPTH levels, TSC levels do not consistently decrease at 5 and 10 min after gland resection. While attractive in terms of cost and availability, intraoperative TSC levels are not clinically reliable in confirming removal of abnormal parathyroid tissue.

Hypothesis: Use of intraoperative measurement of intact parathyroid hormone (iPTH) to confirm complete excision of hyperfunctioning parathyroid tissue does not improve overall operative success rates., Design: Case series of patients undergoing parathyroidectomy with or without intraoperative iPTH measurement., Setting: University teaching hospital., Patients and Interventions: Fifty patients undergoing parathyroidectomy before our institution of intraoperative iPTH sampling in March 1999 (group 1) were compared with 50 patients undergoing parathyroidectomy after this technique was adopted (group 2). Overall, 100 patients underwent operation between December 1996 and May 2000. Serum calcium and iPTH levels were measured at 1- and 3-month intervals. Intraoperative frozen sections and operative times were also analyzed., Results: Mean preoperative calcium levels were 2.85 and 2.82 mmol/L (11.4 and 11.3 mg/dL) in groups 1 and 2, respectively. One-month postoperative calcium values were identical in both groups at 2.35 mmol/L (9.4 mg/dL) (group 1 SD = 0.18 [0.74], group 2 SD = 0.20 [0.82]). At 1 month, all but 1 patient in group 1 had normalized calcium values (2% failure rate), while 3 patients in group 2 (6%) remained hypercalcemic. All 3 patients in group 2 had intraoperative iPTH levels that returned to normal. There was a significant difference in the number of intraoperative frozen sections between groups, with a mean (SD) of 3.4 (1.7) in group 1 and 2.0 (1.6) in group 2 (P<.01). There was no significant difference in operative times between groups., Conclusions: Use of intraoperative iPTH sampling did not significantly affect the overall success of parathyroidectomy, as determined by postoperative normocalcemia. There was, however, a significant decrease in the number of frozen sections sent at operation.

We evaluated the AxSYM troponin I (cTnI) immunoassay for assisting in the detection of acute myocardial infarction (AMI). At four sites, the total imprecision (CV) over 20 days was 6.3-10.2%. The minimum detectable concentration was 0.14 +/- 0.05 microgram/L. Comparison of cTnI measurements between the AxSYM and Stratus (n = 406) over the dynamic range of the AxSYM assay demonstrated good correlation, r = 0.881, with a proportional bias: AxSYM cTnI = 3.50(Stratus cTnI) - 1. 10. The confidence intervals (95%) for the slope and intercept were 3.39-3.64 and -1.32 to -0.95, respectively. The expected cTnI concentration in healthy individuals was /=96%, in skeletal muscle injury, chronic renal disease, and same-day noncardiac surgery patients.

To evaluate the effect of puberty on antipyrine metabolism, we measured antipyrine pharmacokinetics in 17 healthy subjects aged 6-21 years. The subjects received a single oral dose of antipyrine, 18 mg/kg. Salivary antipyrine levels were determined 3, 6, 9, 12 and 24 h after dosing. Age, weight, body surface area and Tanner stage were highly intercorrelated. Volume of distribution (liters) was highly correlated with all of these factors. The weight-corrected clearance of antipyrine declined significantly with age (r = 0.55, p less than 0.025). Patients were classified as immature and other based on serum hormone levels (immature = females with serum estradiol less than 25 pg/ml and males with serum testosterone less than 25 ng/dl). The uncorrected antipyrine clearance was significantly lower in the immature group (mean +/- SD 22.65 +/- 6.04 ml/min) than in others (mean +/- SD 41.30 +/- 13.26; p less than 0.01). This difference disappeared when the weight-corrected antipyrine clearance was compared for these two groups. The change in uncorrected antipyrine clearance with sexual maturation appeared to be due to increased body size, probably related to the adolescent growth spurt.

The aqueous humor of five patients with histologically proven retinoblastoma were analyzed for the main catabolic products of norephinephrine and epinephrine. In each case, there were no detectable levels of normethanephrine, metanephrine, vanilmandelic acid (VMA), and 3-methoxy, 4-hydroxy phenoglycol. The techniques are sensitive to 1 microgram/ml but will not detect the presence of homovanillic acid (HVA).

This article discusses the ideal requirements of office laboratory instruments and analyzes the various operating modes and types of reagents. General and specific features of chemistry and hematology analyzers are presented. Lastly, the financial decision-making process is outlined.