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Importance: Many recent advances in pediatric concussion care are implemented by specialists; however, children with concussion receive care across varied locations. Thus, it is critical to identify which children have access to the most up-to-date treatment strategies., Objective: To evaluate differences in the sociodemographic and community characteristics of pediatric patients who sought care for concussion across various points of entry into a regional health care network., Design, Setting, and Participants: This cross-sectional study included children seen for concussions across a regional US health care network from January 1, 2017, to August 4, 2023. Pediatric patients aged 0 to 18 years who received an International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Clinical Modification code for concussion were included. The study took place at emergency department (ED) and outpatient (primary care [PC] and specialty care [SC]) settings., Exposures: Age at visit, biological sex, parent-identified race and ethnicity, payer type, median income and percentage of adults with a bachelor's degree for home zip code, and overall and subdomain Child Opportunity Index (COI) score based on patient address., Main Outcomes and Measures: The association of exposures with point of entry of ED, PC, and SC were examined in both bivariate analysis and a multinomial logistic regression., Results: Overall, 15 631 patients were included in the study (median [IQR] age, 13 [11-15] years; 7879 [50.4%] male; 1055 [6.7%] Hispanic, 2865 [18.3%] non-Hispanic Black, and 9887 [63.7%] non-Hispanic White individuals). Race and ethnicity were significantly different across settings (1485 patients [50.0%] seen in the ED were non-Hispanic Black vs 1012 [12.0%] in PC and 368 [8.7%] in SC; P < .001) as was insurance status (1562 patients [52.6%] seen in the ED possessed public insurance vs 1624 [19.3%] in PC and 683 [16.1%] in SC; P < .001). Overall and individual COI subdomain scores were also significantly different between settings (overall COI median [IQR]: ED, 30 [9-71]; PC, 87 [68-95]; SC, 87 [69-95]; P < .001). Race, insurance status, and overall COI had the strongest associations with point of entry in the multivariable model (eg, non-Hispanic Black patients seen in the ED compared with non-Hispanic White patients: odds ratio, 2.03; 95% CI, 1.69-2.45)., Conclusions and Relevance: In this cross-sectional study, children with concussion seen in the ED setting were more likely to be non-Hispanic Black, have public insurance, and have a lower Child Opportunity Index compared with children cared for in the PC or SC setting. This highlights the importance of providing education and training for ED clinicians as well as establishing up-to-date community-level resources to optimize care delivery for pediatric patients with concussion at high risk of care inequities.

Objective: The purpose was to examine clinical profiles in concussed children aged 5-9 and 10-12 years and compare them with those of adolescents >12 years., Methods: This study included patients aged 5-18 years presenting to a specialty care concussion program with a sports- and recreation-related (SRR) concussion ≤28 days postinjury. Demographics, injury mechanisms, symptoms, and clinical features were assessed. Chi-squared tests, one-way ANOVA, and Kruskal-Wallis were used for comparisons across age groups., Results: A total of 3280 patients with SRR concussion were included: 5.0% were 5-9 years, 18.4% were 10-12 years, and 76.6% were 13-18 years. Younger age groups had more males than females (5-9 years: 70.7% vs. 29.3%) and more commonly sustained their injury during limited- (28.7%), and non-contact (7.9%) activities compared to other age groups ( p < 0.01). Younger children presented less symptoms frequently ( p ≤ 0.042), but higher symptom severity in somatic and emotional domains ( p ≤ 0.016). Fewer 5-9-year-olds reported changes in school (25.6%), sleep (46.3%), and daily habits (40.9%) than adolescents ( p < 0.001)., Conclusions: Among SRR-concussed children and adolescents, we found significant age-related variations in demographics, injury mechanism, symptoms, and clinical features. Recognizing these unique features in younger children may facilitate targeted management and treatment.

Introduction: Paediatric concussion is a common injury. Approximately 30% of youth with concussion will experience persisting postconcussion symptoms (PPCS) extending at least 1 month following injury. Recently, studies have shown the benefit of early, active, targeted therapeutic strategies. However, these are primarily prescribed from the specialty setting. Early access to concussion specialty care has been shown to improve recovery times for those at risk for persisting symptoms, but there are disparities in which youth are able to access such care. Mobile health (mHealth) technology has the potential to improve access to concussion specialists. This trial will evaluate the feasibility of a mHealth remote patient monitoring (RPM)-based care handoff model to facilitate access to specialty care, and the effectiveness of the handoff model in reducing the incidence of PPCS., Methods and Analysis: This study is a non-randomised type I, hybrid implementation-effectiveness trial. Youth with concussion ages 13-18 will be enrolled from the emergency department of a large paediatric healthcare network. Patients deemed a moderate-to-high risk for PPCS using the predicting and preventing postconcussive problems in paediatrics (5P) stratification tool will be registered for a web-based chat platform that uses RPM to collect information on symptoms and activity. Those patients with escalating or plateauing symptoms will be contacted for a specialty visit using data collected from RPM to guide management. The primary effectiveness outcome will be the incidence of PPCS, defined as at least three concussion-related symptoms above baseline at 28 days following injury. Secondary effectiveness outcomes will include the number of days until return to preinjury symptom score, clearance for full activity and return to school without accommodations. The primary implementation outcome will be fidelity, defined as the per cent of patients meeting specialty care referral criteria who are ultimately seen in concussion specialty care. Secondary implementation outcomes will include patient-defined and clinician-defined appropriateness and acceptability., Ethics and Dissemination: This study was approved by the Institutional Review Board of the Children's Hospital of Philadelphia (IRB 22-019755). Study findings will be published in peer-reviewed journals and disseminated at national and international meetings., Trial Registration Number: NCT05741411., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Concussion is a common injury in the adolescent and young adult populations. Although branched chain amino acid (BCAA) supplementation has shown improvements in neurocognitive and sleep function in pre-clinical animal models of mild-to-moderate traumatic brain injury (TBI), to date, no studies have been performed evaluating the efficacy of BCAAs in concussed adolescents and young adults. The goal of this pilot trial was to determine the efficacy, tolerability, and safety of varied doses of oral BCAA supplementation in a group of concussed adolescents and young adults. The study was conducted as a pilot, double-blind, randomized controlled trial of participants ages 11-34 presenting with concussion to outpatient clinics (sports medicine and primary care), urgent care, and emergency departments of a tertiary care pediatric children's hospital and an urban tertiary care adult hospital, between June 24, 2014 and December 5, 2020. Participants were randomized to one of five study arms (placebo and 15 g, 30 g, 45 g, and 54 g BCAA treatment daily) and followed for 21 days after enrollment. Outcome measures included daily computerized neurocognitive tests (processing speed, the a priori primary outcome; and attention, visual learning, and working memory), symptom score, physical and cognitive activity, sleep/wake alterations, treatment compliance, and adverse events. In total, 42 participants were randomized, 38 of whom provided analyzable data. We found no difference in our primary outcome of processing speed between the arms; however, there was a significant reduction in total symptom score (decrease of 4.4 points on a 0-54 scale for every 500 g of study drug consumed, p value for trend = 0.0036, [uncorrected]) and return to physical activity (increase of 0.503 points on a 0-5 scale for every 500 g of study drug consumed, p value for trend = 0.005 [uncorrected]). There were no serious adverse events. Eight of 38 participants reported a mild (not interfering with daily activity) or moderate (limitation of daily activity) adverse event; there were no differences in adverse events by arm, with only two reported mild adverse events (both gastrointestinal) in the highest (45 g and 54 g) BCAA arms. Although limited by slow enrollment, small sample size, and missing data, this study provides the first demonstration of efficacy, as well as safety and tolerability, of BCAAs in concussed adolescents and young adults; specifically, a dose-response effect in reducing concussion symptoms and a return to baseline physical activity in those treated with higher total doses of BCAAs. These findings provide important preliminary data to inform a larger trial of BCAA therapy to expedite concussion recovery.

Background: A concussion is a common adolescent injury that can result in a constellation of symptoms, negatively affecting academic performance, neurobiological development, and quality of life. Mobile health (mHealth) technologies, such as apps for patients to report symptoms or wearables to measure physiological metrics like heart rate, have been shown to be promising in health maintenance. However, there is limited evidence about mHealth engagement in adolescents with a concussion during their recovery course., Objective: This study aims to determine the response rate and response rate patterns in concussed adolescents reporting their daily symptoms through mHealth technology. It will also examine the effect of time-, demographic-, and injury-related characteristics on response rate patterns., Methods: Participants aged between 11-18 years (median days since injury at enrollment: 11 days) were recruited from the concussion program of a tertiary care academic medical center and a suburban school's athletic teams. They were asked to report their daily symptoms using a mobile app. Participants were prompted to complete the Post-Concussion Symptom Inventory (PCSI) 3 times (ie, morning, afternoon, and evening) per day for 4 weeks following enrollment. The primary outcome was the response rate pattern over time (by day since initial app use and the day since injury). Time-, demographic-, and injury-related differences in reporting behaviors were compared using Mann Whitney U tests., Results: A total of 56 participants were enrolled (mean age 15.3, SD 1.9 years; n=32, 57% female). The median response rate across all days of app use in the evening was 37.0% (IQR 27.2%-46.4%), which was significantly higher than the morning (21.2%, IQR 15.6%-30.5%) or afternoon (26.4%, IQR 21.1%-31.5%; P<.001). The median daily response was significantly different by sex (female: 53.8%, IQR 46.2%-64.2% vs male: 42.0%, IQR 28.6%-51.1%; P=.003), days since injury to app use (participants starting to use the app >7 days since injury: 54.1%, IQR 47.4%-62.2% vs starting to use the app ≤7 days since injury: 38.0%, IQR 26.0%-53.3%; P=.002), and concussion history (participants with a history of at least one prior concussion: 57.4%, IQR 44.5%-70.5% vs participants without concussion history: 42.3%, IQR 36.8%-53.5%; P=.03). There were no significant differences by age. Differences by injury mechanism (sports- and recreation-related injury: 39.6%, IQR 36.1%-50.4% vs non-sports- or recreation-related injury: 30.6%, IQR 20.0%-42.9%; P=.04) and initial symptom burden (PCSI scores greater than the median score of 47: 40.9%, IQR 35.2%-53.8% vs PCSI scores less than or equal to the median score: 31.9%, IQR 24.6%-40.6%; P=.04) were evident in the evening response rates; however, daily rates were not statistically different., Conclusions: Evening may be the optimal time to prompt for daily concussion symptom assessment among concussed adolescents compared with morning or afternoon. Multiple demographic- and injury-related characteristics were associated with higher daily response rates, including for female participants, those with more than 1 week from injury to beginning mHealth monitoring, and those with a history of at least one previous concussion. Future studies may consider incentive strategies or adaptive digital concussion assessments to increase response rates in populations with low engagement., (© Sicong Ren, Catherine C McDonald, Daniel J Corwin, Douglas J Wiebe, Christina L Master, Kristy B Arbogast. Originally published in JMIR Pediatrics and Parenting (https://pediatrics.jmir.org).)

Importance: Mood disorders are prevalent among adolescents and young adults, and their onset often coincides with driving eligibility. The understanding of how mood disorders are associated with youth driving outcomes is limited., Objective: To examine the association between the presence of a mood disorder and rates of licensing, crashes, violations, and suspensions among adolescents and young adults., Design, Setting, and Participants: This cohort study was conducted among New Jersey residents who were born 1987 to 2000, age eligible to acquire a driver's license from 2004 to 2017, and patients of the Children's Hospital of Philadelphia network within 2 years of licensure eligibility at age 17 years. The presence of a current (ie, ≤2 years of driving eligibility) mood disorder was identified using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) or International Statistical Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) codes. Rates of licensure and driving outcomes among youths who were licensed were compared among 1879 youths with and 84 294 youths without a current mood disorder from 2004 to 2017. Data were analyzed from June 2022 to July 2023., Main Outcomes and Measures: Acquisition of a driver's license and first involvement as a driver in a police-reported crash and rates of other adverse driving outcomes were assessed. Survival analysis was used to estimate adjusted hazard ratios (aHRs) for licensing and driving outcomes. Adjusted rate ratios (aRRs) were estimated for driving outcomes 12 and 48 months after licensure., Results: Among 86 173 youths (median [IQR] age at the end of the study, 22.8 [19.7-26.5] years; 42 894 female [49.8%]), there were 1879 youths with and 84 294 youths without a mood disorder. A greater proportion of youths with mood disorders were female (1226 female [65.2%]) compared with those without mood disorders (41 668 female [49.4%]). At 48 months after licensure eligibility, 75.5% (95% CI, 73.3%-77.7%) and 83.8% (95% CI, 83.5%-84.1%) of youths with and without mood disorders, respectively, had acquired a license. Youths with mood disorders were 30% less likely to acquire a license than those without a mood disorder (aHR, 0.70 [95% CI, 0.66-0.74]). Licensed youths with mood disorders had higher overall crash rates than those without mood disorders over the first 48 months of driving (137.8 vs 104.8 crashes per 10 000 driver-months; aRR, 1.19 [95% CI, 1.08-1.31]); licensed youths with mood disorders also had higher rates of moving violations (aRR, 1.25 [95% CI, 1.13-1.38]) and license suspensions (aRR, 1.95 [95% CI, 1.53-2.49])., Conclusions and Relevance: This study found that youths with mood disorders were less likely to be licensed and had higher rates of adverse driving outcomes than youths without mood disorders. These findings suggest that opportunities may exist to enhance driving mobility in this population and elucidate the mechanisms by which mood disorders are associated with crash risk.

Background: Pre-existing mental health diagnoses may contribute to greater emotional symptom burden and prolonged recovery after concussion., Hypothesis: Youth with pre-existing mental health diagnoses will have greater emotional symptom burden, greater risk for delayed return to exercise, and more prolonged recovery from concussion than those without those diagnoses., Study Design: Prospective cohort., Level of Evidence: Level 3., Methods: A prospective registry of youth concussion was examined for differences in emotional symptom burden after injury to develop a predictive risk model for prolonged recovery. The impact of individual and total number of pre-existing mental health diagnoses (0, 1, 2, and 3+) was assessed, and multivariable logistic regression was performed to identify factors associated with prolonged recovery., Results: Among a cohort of 3105 youth with concussion, those with a history of mental health diagnoses, in a dose-response fashion, had greater postinjury emotional symptom burden (7 emotional symptoms vs 4; P < 0.01), visio-vestibular dysfunction (65% abnormal vs 56% abnormal; P < 0.01), later return to symptom-limited exercise (23 vs 21 days; P < 0.01), and overall longer concussion recovery (38 days, interquartile range [IQR] 18, 80) versus 25 days (IQR 13, 54; P < 0.01). Boys with prolonged recovery after concussion had greater emotional symptom burden than girls (5 emotional symptoms vs 3; P < 0.01)., Conclusion: Pre-existing mental health diagnoses are associated with greater postinjury emotional symptom burden and longer concussion recovery in a dose-response fashion. Visiovestibular deficits and delayed return to exercise are also associated with pre-existing mental health diagnoses and prolonged recovery. Boys with prolonged recovery from concussion experience greater emotional symptom burden than girls., Clinical Relevance: Addressing pre-existing mental health diagnoses is essential to concussion management. Boys with prolonged recovery from concussion may particularly benefit from interventions to address their higher emotional symptom burden. Interventions, including a home visio-vestibular exercise program and symptom-limited exercise, may contribute to improving time to concussion recovery., Competing Interests: The following author declared potential conflicts of interest: C.L.M. has received speaking fees from the AAP, AAOPT, Indiana University, Nationwide Children’s Hospital, and NYU Concussion.

Background: While concussions are common pediatric injuries, a lack of agreement on a standard definition of recovery creates multiple challenges for clinicians and researchers alike., Hypothesis: The percentage of concussed youth deemed recovered as part of a prospective cohort study will differ depending on the recovery definition., Study Design: Descriptive epidemiologic study of a prospectively enrolled observational cohort., Level of Evidence: Level 3., Methods: Participants aged 11 to 18 years were enrolled from the concussion program of a tertiary care academic center. Data were collected from initial and follow-up clinical visits ≤12 weeks from injury. A total of 10 recovery definitions were assessed: (1) cleared to full return to sports; (2) return to full school; (3) self-reported return to normal; (4) self-reported full return to school; (5) self-reported full return to exercise; (6) symptom return to preinjury state; (7) complete symptom resolution; (8) symptoms below standardized threshold; (9) no abnormal visio-vestibular examination (VVE) elements; and (10) ≤1 abnormal VVE assessments., Results: In total, 174 participants were enrolled. By week 4, 63.8% met at least 1 recovery definition versus 78.2% by week 8 versus 88.5% by week 12. For individual measures of recovery at week 4, percent recovered ranged from 5% by self-reported full return to exercise to 45% for ≤1 VVE abnormality (similar trends at 8 and 12 weeks)., Conclusion: There is wide variability in the proportion of youth considered recovered at various points following concussion depending on the definition of recovery, with higher proportions using physiologic examination-based measures and lower proportions using patient-reported measures., Clinical Relevance: These results further emphasize the need for a multimodal assessment of recovery by clinicians as a single and standardized definition of recovery that captures the broad impact of concussion on a given patient continues to be elusive., Competing Interests: The following authors declared potential conflicts of interest: K.B.M., C.C.M., M.R.P., K.B.A., and C.L.M. received a grant from Pennsylvania Department of Health (DOH). K.B.A. and C.L.M. received grant R01NS097549 from the National Institute of Neurological Disorders and Stroke.

Context: Multiple clinical evaluation tools exist for adolescent concussion with various degrees of correlation, presenting challenges for clinicians in identifying which elements of these tools provide the greatest diagnostic utility., Objective: To determine the combination of elements from 4 commonly used clinical concussion batteries that maximize discrimination of adolescents with concussion from those without concussion., Design: Cross-sectional study., Setting: Suburban school and concussion program of a tertiary care academic center., Patients or Other Participants: A total of 231 participants with concussion (from a suburban school and a concussion program) and 166 participants without concussion (from a suburban school) between the ages of 13 and 19 years., Main Outcome Measure(s): Individual elements of the visio-vestibular examination (VVE), Sport Concussion Assessment Tool, fifth edition (SCAT5; including the modified Balance Error Scoring System), King-Devick test (K-D), and Postconcussion Symptom Inventory (PCSI) were evaluated. The 24 subcomponents of these tests were grouped into interpretable factors using sparse principal component analysis. The 13 resultant factors were combined with demographic and clinical covariates into a logistic regression model and ranked by frequency of inclusion into the ideal model, and the predictive performance of the ideal model was compared with each of the clinical batteries using the area under the receiver operating characteristic curve (AUC)., Results: A cluster of 4 factors (factor 1 [VVE saccades and vestibulo-ocular reflex], factor 2 [modified Balance Error Scoring System double-legged stance], factor 3 [SCAT5/PCSI symptom scores], and factor 4 [K-D completion time]) emerged. A model fit with the top factors performed as well as each battery in predicting concussion status (AUC = 0.816 [95% CI = 0.731, 0.889]) compared with the SCAT5 (AUC = 0.784 [95% CI = 0.692, 0.866]), PCSI (AUC = 0.776 [95% CI = 0.674, 0.863]), VVE (AUC = 0.711 [95% CI = 0.602, 0.814]), and K-D (AUC = 0.708 [95% CI = 0.590, 0.819])., Conclusions: A multifaceted assessment for adolescents with concussion, comprising symptoms, attention, balance, and the visio-vestibular system, is critical. Current diagnostic batteries likely measure overlapping domains, and the sparse principal component analysis demonstrated strategies for streamlining comprehensive concussion assessment across a variety of settings., (© by the National Athletic Trainers’ Association, Inc.)

Visual and vestibular deficits, as measured by a visio-vestibular examination (VVE), are markers of concussion in youth. Little is known about VVE evolution post-injury, nor influence of age or sex on trajectory. The objective was to describe the time trend of abnormal VVE elements after concussion. Two cohorts, 11-18 years, were enrolled: healthy adolescents ( n  = 171) from a high school with VVE assessment before or immediately after their sport seasons and concussed participants ( n  = 255) from a specialty care concussion program, with initial assessment ≤28 days from injury and VVE repeated throughout recovery during clinical visits. The primary outcome, compared between groups, is the time course of recovery of the VVE examination, defined as the probability of an abnormal VVE (≥2/9 abnormal elements) and modeled as a cubic polynomial of days after injury. We explored whether probability trajectories differed by: age (<14 years vs. 14+ years), sex, concussion history (0 versus 1+), and days from injury to last assessment (≤28 days vs. 29+ days). Overall, abnormal VVE probability peaked at 0.57 at day 8 post-injury, compared with an underlying prevalence of 0.083 for uninjured adolescents. Abnormal VVE probability peaked higher for those 14+ years, female, with a concussion history and whose recovery course was longer than 28 days post-injury, compared with their appropriate strata subgroups. Females and those <14 years demonstrated slower resolution of VVE abnormalities. VVE deficits are common in adolescents after concussion, and the trajectory of resolution varies by age, sex, and concussion history. These data provide insight to clinicians managing concussions on the timing of deficit resolution after injury.

Anemia and leukopenia because of copper deficiency can be mistaken for myelodysplasia. Key issues, including response to G-CSF and oral copper, are discussed. This case illustrates a significant deleterious effect of excessive zinc consumption., Competing Interests: None declared., (© 2020 The Authors. Clinical Case Reports published by John Wiley & Sons Ltd.)

Purpose: Evaluate the discriminatory ability of two clinical measures and one device-based measure of gait and balance for concussed youth., Methods: We enrolled 81 cases and 90 controls age 14-18 yr old from August 2017 to June 2018. Controls were recruited from a suburban high school, and cases were recruited from the concussion program of an academic pediatric tertiary care center. Tests included two clinical measures: 1) complex tandem gait, scored as sway/errors walking forward and backward eyes open and closed; 2) Modified Balance Error Scoring System (mBESS), scored as total number of errors on three standing tasks; and one device-based measure; 3) Modified Clinical Test of Sensory Interaction and Balance (mCTSIB) using the Biodex Biosway Balance System, scored as a sway index. Sensitivity, specificity, ideal cutpoint, and area under the receiver operating characteristic curve (AUC) were calculated for all test components., Results: Ideal cutpoint for total number of sway/errors for tandem gait = 5, sensitivity 41%, specificity 90%. Ideal cutpoint for total mBESS errors = 4, sensitivity 55%, specificity 75%. Ideal cutpoint for mCTSIB = 1.37, sensitivity 37%, specificity 88%. Among each test, some individual components outperformed overall composites, in particular tandem gait (specificity forward eyes open = 99%, sensitivity backward eyes closed = 81%). Among the 40 cases and 65 controls with all three assessments, AUC (95% CI) for tandem gait = 0.63 (0.52,0.75), mBESS = 0.70 (0.60,0.81), and mCTSIB = 0.54 (0.42,0.66)., Conclusions: A device-based measure of balance did not produce better discriminatory ability than two clinical assessments. Complex tandem gait has the additional benefit of being an easy-to-perform and graded test with highly sensitive and specific individual components.

Objective: The College of American Pathologists Cell Markers Committee designed a study to evaluate the use of immunohistochemistry primary antibodies beyond manufacturers' recommended dates., Methods: Pathologists were asked to save aliquots of primary antibodies during mid-1997 so that by spring 1998 the reagents would be "outdated" according to manufacturers' recommendations. Three tumors were immunostained both in mid-1997 and early 1998 (using outdated reagents in 1998). Two hundred twenty-one laboratories participated., Patient Samples: Immunostained materials consisted of an angiomyolipoma immunostained for muscle-specific actin and HMB-45, a melanoma immunostained for S100 protein and HMB-45, and a large cell lymphoma immunostained for common leukocyte antigen and HMB-45. Blocks from the same tumor were used in each instance., Main Outcome Measure: We compared the immunostaining results as a percentage of laboratories indicating a positive or negative immunohistochemical result between the 1997 and 1998 time points., Results: Only minor differences were identified for the 221 reporting laboratories in 1998 as compared with those in 1997., Conclusions: The data suggest review of the Health Care Financing Administration's ruling on extending the useful reagent shelf life beyond manufacturers recommendations. Similar studies using more inherently quantitative methodology are suggested.

This review discusses several commonly used lineage-directed antibodies, including those to cytokeratins, vimentin, glial fibrillary acidic protein, neurofilaments, desmin, actin, leukocyte common antigen, and melanoma-specific antigen. Discussion is particularly directed to issues of antibody sensitivity and specificity, with several confusing and/or potentially beneficial examples of cross-lineage antigenic co-expression cited. The value of using limited panels composed of antibodies with complementary specificities is also emphasized.

Immunohistochemical techniques have become commonplace adjunctive aids in anatomic pathology. Although much has been written describing modifications of the basic techniques, sensitivity, and specificity of reagents, little has been published regarding the interlaboratory variability in immunostain results on a given test sample. The Cell Markers Survey of the College of American Pathologists was organized to address this question of interlaboratory variability and to disseminate information on the techniques and reagents currently available.