College Of American Pathologists Survey Research Articles

Pancreaticobiliary Cytology Practice in 2021: Results of a College of American Pathologists Survey.

The College of American Pathologists (CAP) surveys provide national benchmarks of pathology practice. To investigate pancreaticobiliary cytology practice in domestic and international laboratories in 2021. We analyzed data from the CAP Pancreaticobiliary Cytology Practice Supplemental Questionnaire that was distributed to laboratories participating in the 2021 CAP Nongynecologic Cytopathology Education Program. Ninety-three percent (567 of 612) of respondent laboratories routinely evaluated pancreaticobiliary cytology specimens. Biliary brushing (85%) was the most common pancreaticobiliary cytology specimen evaluated, followed by pancreatic fine-needle aspiration (79%). The most used sampling methods reported by 235 laboratories were 22-gauge needle for fine-needle aspiration (62%) and SharkCore needle for fine-needle biopsy (27%). Cell block was the most used slide preparation method (76%), followed by liquid-based cytology (59%) for pancreatic cystic lesions. Up to 95% (303 of 320) of laboratories performed rapid on-site evaluation (ROSE) on pancreatic solid lesions, while 56% (180 of 320) performed ROSE for cystic lesions. Thirty-six percent (193 of 530) of laboratories used the Papanicolaou Society of Cytopathology System for Reporting Pancreaticobiliary Cytology in 2021. Among all institution types, significant differences in specimen volume, specimen type, ROSE practice, and case sign-out were identified. Additionally, significant differences in specimen type, slide preparation, and ROSE practice were found. This is the first survey from the CAP to investigate pancreaticobiliary cytology practice. The findings reveal significant differences among institution types and between domestic and international laboratories. These data provide a baseline for future studies in a variety of practice settings.

Navigating Practice Issues Related to the Unsatisfactory Cervicovaginal Papanicolaou Test: Survey Results of Laboratories Participating in the 2020 College of American Pathologists PAP Education Program.

Unsatisfactory Papanicolaou (Pap) tests pose a unique set of challenges to the laboratory with regard to their processing, review, reporting, and performance of human papillomavirus (HPV) testing. There are no standardized guidelines for the review process and handling of unsatisfactory Pap tests. To assess the current practice patterns regarding various aspects of the unsatisfactory Pap test, from processing to reporting, across laboratories worldwide. A supplemental questionnaire was mailed to laboratories participating in the 2020 College of American Pathologists (CAP) Gynecologic Cytopathology (PAP Education) Program, requesting data regarding the unsatisfactory Pap test. Of 1520 participating laboratories, 619 (40.7%) responded, and the responses of 577 laboratories were included for further analysis. Only 64.6% (373 of 577) laboratories used the unsatisfactory Pap test criteria as specified by the 2014 Bethesda System. About three-quarters of the respondents (433 of 576; 75.2%) routinely rescreened unsatisfactory Pap tests. Routine repreparation of such Pap tests was performed by 54.9% (316 of 576) of laboratories, and 52.0% (293 of 563) used glacial acetic acid for repreparing excessively bloody specimens. HPV test results were reported for unsatisfactory Pap tests, always or sometimes, by 62.4% (353 of 566) of respondents. This CAP survey reveals important information regarding the practice patterns pertaining to several aspects of the unsatisfactory Pap test. It also provides valuable insight into the quality assurance measures that can be implemented for such tests. Future studies can further aid in the standardization of all components of the handling of unsatisfactory Pap tests for overall quality improvement.

Four-Year Laboratory Performance of the First College of American Pathologists In Silico Next-Generation Sequencing Bioinformatics Proficiency Testing Surveys.

In 2016, the College of American Pathologists (CAP) launched the first next-generation sequencing (NGS) in silico bioinformatics proficiency testing survey to evaluate the performance of clinical laboratory bioinformatics pipelines for the detection of oncology-associated variants at varying allele fractions. This survey focused on 2 commonly used oncology panels, the Illumina TruSeq Amplicon Cancer Panel and the Thermo Fisher Ion AmpliSeq Cancer Hotspot v2 Panel. To review the analytical performance of laboratories participating in the CAP NGS bioinformatics (NGSB) surveys, comprising NGSB1 for Illumina users and NGSB2 for Thermo Fisher Ion Torrent users, between 2016 and 2019. Responses from 78 laboratories were analyzed for accuracy and associated performance characteristics. The analytical sensitivity was 90.0% (1901 of 2112) for laboratories using the Illumina platform and 94.8% (2153 of 2272) for Thermo Fisher Ion Torrent users. Variant type and variant allele fraction were significantly associated with performance. False-negative results were seen mostly for multi-nucleotide variants and variants engineered at variant allele fractions of less than 25%. Analytical specificity for all participating laboratories was 99.8% (9303 of 9320). There was no statistically significant association between deletion-insertion length and detection rate. These results demonstrated high analytical sensitivity and specificity, supporting the feasibility and utility of using in silico mutagenized NGS data sets as a supplemental challenge to CAP surveys for oncology-associated variants based on physical samples. This program demonstrates the opportunity and challenges that can guide future surveys inclusive of customized in silico programs.

Improved Performance in Measurement of Serum Cystatin C by Laboratories Participating in the College of American Pathologists 2019 CYS Survey.

Use of cystatin C for glomerular filtration rate estimation (eGFR) has garnered heightened interest as a means to avoid race-based medicine, since eGFRcys equations do not require specification of race. Before considering more widespread use of cystatin C, it is important to confirm that assays provide accurate measurements of cystatin C concentration, to ensure accurate GFR estimates. To determine if the accuracy of cystatin C measurements in laboratories participating in the College of American Pathologists (CAP) Cystatin C (CYS) survey has improved since 2014. Two fresh frozen serum pools, the first from healthy donors without chronic kidney disease (CKD), and the second from patients with CKD, along with a synthetically prepared elevated cystatin C pool, were sent to laboratories participating in the 2019 CYS-A survey. Target values were established by using 2 immunoassays and a bracketed 2-point calibration with diluted ERM-DA471/IFCC reference material. For the healthy donor fresh frozen pool (ERM-DA471/IFCC-traceable target of 0.725 mg/L), the all-method mean (standard deviation, coefficient of variation) was 0.731 mg/L (0.071, 9.7%). For the CKD pool (ERM-DA471/IFCC-traceable target of 2.136 mg/L), the all-method mean was 2.155 mg/L (0.182, 8.4%). For the synthetically spiked pool (ERM-DA471/IFCC-traceable target of 1.843 mg/L), the all-method mean was 1.886 mg/L (0.152, 8.1%). This represents marked improvement in accuracy and between-method agreement compared to the 2014 CAP survey. Manufacturers have markedly improved accuracy and between-method agreement of cystatin C measurement procedures since 2014, which allows for greater confidence in estimated GFR relying on cystatin C.

Rescreening Practices of Negative Papanicolaou Tests With Positive Human Papillomavirus Test Result.

The yield of the prospective rescreening process for "negative for intraepithelial lesion or malignancy" (NILM) Papanicolaou (Pap) tests is higher with the inclusion of a greater proportion of high-risk cases. One of the suggested criteria for classifying a Pap test finding as high risk is recent or concurrent high-risk human papillomavirus (HPV) positivity. To evaluate how the results of HPV testing have been incorporated in the prospective rescreening of NILM Pap tests across a wide range of laboratories. A questionnaire survey was sent to laboratories participating in the 2019 College of American Pathologists (CAP) Gynecologic Cytology (PAP Education) Program. Of the 1507 participating laboratories, 667 (44%) responded to the survey. Most laboratories (59.4%; 396 of 667) had not incorporated HPV test/genotyping results to select NILM Pap tests for rescreening. Amongst the remaining laboratories, for NILM HPV-positive Pap test results, 112 (16.8%) had a policy to rescreen by a cytotechnologist only, 51 (7.6%) by a pathologist only, and 86 (12.9%) by both. Of 264 laboratories, 181 (68.6%) reported the cytology upon availability of the HPV test result and completion of the secondary review. Of 661 laboratories, 145 (21.9%) included consensus-type recommendations in the cytology report for such Pap tests. This CAP survey provides significant information regarding the current trends in the use of HPV test results in prospective rescreening of NILM Pap tests. Future studies on quality improvement can further assist in the standardization of this process across different laboratories.

Breast Specimen Processing and Reporting With an Emphasis on Margin Evaluation: A College of American Pathologists Survey of 866 Laboratories.

- The College of American Pathologists (CAP) developed protocols for reporting pathologic characteristics of breast cancer specimens, including margin status. The Society of Surgical Oncology (SSO) and the American Society for Radiation Oncology (ASTRO) published treatment guidelines regarding margins in patients with invasive cancer; and SSO, ASTRO, and the American Society of Clinical Oncology (ASCO) recently published guidelines for patients with ductal carcinoma in situ. - To assess current practices among pathologists with regard to the processing/reporting of breast specimens, assess compliance with CAP cancer protocols, and assess alignment with SSO/ASTRO and SSO/ASTRO/ASCO guidelines. - A survey concerning breast specimen processing/reporting was distributed to pathologists enrolled in the CAP Performance Improvement Program in Surgical Pathology. - Ninety-four percent (716 of 764 respondents) and 91% (699 of 769 respondents) define positive margins as "tumor on ink" for invasive cancer and ductal carcinoma in situ, respectively, in compliance with CAP cancer protocols and with SSO/ASTRO and SSO/ASTRO/ASCO guidelines. Of 791 respondents who provided details regarding methods for margin evaluation, 608 (77%) exclusively examine perpendicular margins, facilitating guideline compliance. However, 183 of 791 respondents (23%) examine en face margins in at least a subset of specimens, which may preclude guideline compliance in some cases. When separate cavity (shave) margins are examined, while 517 of 586 respondents (88%) ink these specimens, 69 of 586 (12%) do not, and this may also preclude guideline compliance in some cases. - A substantial proportion of survey participants report margin status for breast cancer specimens in a manner consistent with CAP cancer protocols, and in alignment with SSO/ASTRO and SSO/ASTRO/ASCO guidelines. However, there are opportunities for some laboratories to modify procedures in order to facilitate more complete adherence to guidelines.

Survey of Irradiation Practice for the Prevention of Transfusion-Associated Graft-versus-Host Disease.

-Transfusion-associated graft-versus-host disease is a rare, often fatal complication of cellular blood product transfusion. The requirement that at-risk groups receive irradiated products reduces the incidence of transfusion-associated graft-versus-host disease. A comprehensive survey of irradiation practices has not been performed since 1989; meanwhile, new indications for irradiation have emerged. -To assess current irradiation practices at College of American Pathologists member institutions. Changes in irradiation practice indicated by comparing results of a survey of irradiation practices in 1989 with those of a survey performed in 2014 may reveal how the field has developed and what areas (if any) remain to be improved. -A supplemental College of American Pathologists survey was sent out with questions regarding irradiation practices for specific conditions and circumstances. The questions included conditions for which irradiation is generally considered required for the prevention of transfusion-associated graft-versus-host disease as well as those not considered to be a special risk. -An average of 2100 organizations responded to each question regarding their irradiation practices. Irradiation for transfusion from blood relatives, human leukocyte antigen-matched products, preterm infants, and Hodgkin disease were the most common indications cited. A few organizations had universal irradiation, whereas others irradiated products by floor/unit or by service. -For some at-risk populations irradiation of cellular blood products is more common than in 1989, whereas for others this practice has been reduced. Although gains have been made since the last national survey of irradiation practices, work remains to eliminate the possibility of transfusion-associated graft-versus-host disease from known at-risk populations.

Report on HbA1c Proficiency Testing in Asia in 2012.

In 2010, the Japan Diabetes Society decided to introduce the National Glycohemoglobin Standardization Program (NGSP) values into clinical practice. Accordingly, NGSP Certification of Japanese manufacturers of HbA1c-related diagnostic reagents and instruments was initiated in February, 2012, through an NGSP network laboratory, the Asian Secondary Reference Laboratory (ASRL) #1. Traceability to the NGSP reference system can be endorsed by manufacturer certification, as well as by the College of American Pathologists (CAP) survey. Nevertheless, only a few manufacturers participate in the CAP survey in Japan. Thus, proficiency testing (PT) was proposed and executed by ASRL #1. Single-donor whole-blood samples were used for the PT. The participated measurement systems were NGSP certified. Twenty-two laboratories obtained certification through ASRL #1; 2 through the Secondary Reference Laboratory (SRL) #8; and 9 through the SRL #9. The combination plots of the bias data in this PT and in the NGSP certification performed in March and May in 2012 were consistent with each other: mean NGSP values at each level agreed well with the target value. In conclusion, PT using whole blood is useful in endorsing NGSP certification.

Summary of Microsatellite Instability Test Results From Laboratories Participating in Proficiency Surveys: Proficiency Survey Results From 2005 to 2012

The College of American Pathologists surveys are the largest laboratory peer comparison programs in the world. These programs allow laboratories to regularly evaluate their performance and improve the accuracy of the patient test results they provide. Proficiency testing is offered twice a year to laboratories performing microsatellite instability testing. These surveys are designed to emulate clinical practice, and some surveys have more challenging cases to encourage the refinement of laboratory practices. This report summarizes the results and trends in microsatellite instability proficiency testing from participating laboratories from the inception of the program in 2005 through 2012. We compiled and analyzed data for 16 surveys of microsatellite instability proficiency testing during 2005 to 2012. The number of laboratories participating in the microsatellite instability survey has more than doubled from 42 to 104 during the 8 years analyzed. An average of 95.4% of the laboratories correctly classified each of the survey test samples from the 2005A through 2012B proficiency challenges. In the 2011B survey, a lower percentage of laboratories (78.4%) correctly classified the specimen, possibly because of overlooking subtle changes of microsatellite instability and/or failing to enrich the tumor content of the specimen to meet the limit of detection of their assay. In general, laboratories performed well in microsatellite instability testing. This testing will continue to be important in screening patients with colorectal and other cancers for Lynch syndrome and guiding the management of patients with sporadic colorectal cancer.

Immunohistochemistry Validation Procedures and Practices: A College of American Pathologists Survey of 727 Laboratories

The immunohistochemistry (IHC) laboratory represents a dynamic area of surgical pathology with limited practice guidelines. Studies have shown significant interlaboratory variability in results. To establish baseline parameters for IHC validation procedures and practice, and to assess their feasibility of implementation. In September 2010, a questionnaire was distributed by the College of American Pathologists. It was composed of 32 questions relating to nonpredictive assays as well as non-US Food and Drug Administration (non-FDA)-approved, predictive IHC assays other than human epidermal growth factor 2 (HER2/neu). For non-FDA approved, nonpredictive IHC assays, 68% of laboratories had a written validation procedure. Eighty-six percent of laboratories validated the most recently introduced nonpredictive antibody. Seventy-five percent used 21 or fewer total cases for the validation and 40% used weakly or focally positive cases. Forty-six percent of respondents had a written procedure for validation procedures for non-FDA approved, predictive marker IHC assays other than HER2/neu. Seventy-five percent of laboratories validated the most recently introduced predictive antibody other than HER2/neu. Fewer than half used 25 or more cases for the validation, and 47% used weakly or focally positive cases. Some laboratories have written validation procedures that appear to build upon HER2/neu testing guidelines. Some laboratories also manage to validate new antibodies according to those standards; however, many do not. There appears to be a need for further validation guideline development for nonpredictive and non-FDA approved predictive antibody IHC assays.

Are There Barriers to the Release of Paraffin Blocks for Clinical Research Trials? A College of American Pathologists Survey of 609 Laboratories

Are There Barriers to the Release of Paraffin Blocks for Clinical Research Trials? A College of American Pathologists Survey of 609 Laboratories

Are There Barriers to the Release of Paraffin Blocks for Clinical Research Trials? A College of American Pathologists Survey of 609 Laboratories

Abstract Context.—The number of paraffin blocks submitted for patients enrolled in clinical research trials appears to be declining. Objective.—To obtain information on laboratory policies and procedures in complying with requests to submit paraffin blocks for research. Design.—A questionnaire was sent to members of a voluntary market research panel composed of pathologists representing a broad spectrum of experience and practice settings. The questions addressed departmental policies and the likely responses to requests to submit pathology materials for patients enrolled in clinical trials. Results.—The survey was completed by 609 of 762 pathologists (80%) who responded to the invitation. More than 90% of respondents stated that they comply with these requests. Although 14% have a policy precluding the release of blocks for research, 84% of those will send limited tissue samples in lieu of blocks. When tumor is confined to a single block, most laboratories will not release the block but will send unstain...

Are There Barriers to the Release of Paraffin Blocks for Clinical Research Trials? A College of American Pathologists Survey of 609 Laboratories

The number of paraffin blocks submitted for patients enrolled in clinical research trials appears to be declining. To obtain information on laboratory policies and procedures in complying with requests to submit paraffin blocks for research. A questionnaire was sent to members of a voluntary market research panel composed of pathologists representing a broad spectrum of experience and practice settings. The questions addressed departmental policies and the likely responses to requests to submit pathology materials for patients enrolled in clinical trials. The survey was completed by 609 of 762 pathologists (80%) who responded to the invitation. More than 90% of respondents stated that they comply with these requests. Although 14% have a policy precluding the release of blocks for research, 84% of those will send limited tissue samples in lieu of blocks. When tumor is confined to a single block, most laboratories will not release the block but will send unstained slides. Very few laboratories require reimbursement before releasing tissues. Pathologists attempt to comply with requests for materials but usually refuse to release the only diagnostic paraffin block so that materials are retained for possible future needs. Other problems identified in this survey include difficulties in getting blocks returned when needed and poor communication between researchers and laboratories. Lack of reimbursement and inadequate consent are not significant barriers to release of materials.

Identification of a novel HLA‐DQB1 allele, DQB1*0326, in a College of American Pathologists 2009 survey specimen

We identified a novel DQB1*0326 allele from a proficiency test sample provided by the College of American Pathologists (CAP) medical society. This novel DQB1 allele was unexpectedly discovered by sequence-based typing method in an attempt to resolve a discrepant typing result between the CAP survey report and our laboratory report. This novel DQB1 allele is most similar to DQB1*030302 and DQB1*0311. DQB1*0326 has a nucleotide substitution resulting an amino acid change when compared with DQB1*030302 (M to L) and it differs from DQB1*0311 by one nucleotide variation causing an amino acid replacement (A to D).

Laboratory Compliance With the American Society of Clinical Oncology/College of American Pathologists Guidelines for Human Epidermal Growth Factor Receptor 2 Testing: A College of American Pathologists Survey of 757 Laboratories

Abstract Context.—To ensure quality human epidermal growth receptor 2 (HER2) testing in breast cancer, the American Society of Clinical Oncology/College of American Pathologists guidelines were introduced with expected compliance by 2008. Objective.—To assess the effect these guidelines have had on pathology laboratories and their ability to address key components. Design.—In late 2008, a survey was distributed with the HER2 immunohistochemistry (IHC) proficiency testing program. It included questions regarding pathology practice characteristics and assay validation using fluorescence in situ hybridization or another IHC laboratory assay and assessed pathologist HER2 scoring competency. Results.—Of the 907 surveys sent, 757 (83.5%) were returned. The median laboratory accessioned 15 000 cases and performed 190 HER2 tests annually. Quantitative computer image analysis was used by 33% of laboratories. In-house fluorescence in situ hybridization was performed in 23% of laboratories, and 60% of laboratories a...

Laboratory Compliance With the American Society of Clinical Oncology/College of American Pathologists Guidelines for Human Epidermal Growth Factor Receptor 2 Testing: A College of American Pathologists Survey of 757 Laboratories

To ensure quality human epidermal growth receptor 2 (HER2) testing in breast cancer, the American Society of Clinical Oncology/College of American Pathologists guidelines were introduced with expected compliance by 2008. To assess the effect these guidelines have had on pathology laboratories and their ability to address key components. In late 2008, a survey was distributed with the HER2 immunohistochemistry (IHC) proficiency testing program. It included questions regarding pathology practice characteristics and assay validation using fluorescence in situ hybridization or another IHC laboratory assay and assessed pathologist HER2 scoring competency. Of the 907 surveys sent, 757 (83.5%) were returned. The median laboratory accessioned 15 000 cases and performed 190 HER2 tests annually. Quantitative computer image analysis was used by 33% of laboratories. In-house fluorescence in situ hybridization was performed in 23% of laboratories, and 60% of laboratories addressed the 6- to 48-hour tissue fixation requirement by embedding tissue on the weekend. HER2 testing was performed on the initial biopsy in 40%, on the resection specimen in 6%, and on either in 56% of laboratories. Testing was validated with only fluorescence in situ hybridization in 47% of laboratories, whereas 10% of laboratories used another IHC assay only; 13% used both assays, and 12% and 15% of laboratories had not validated their assays or chose "not applicable" on the survey question, respectively. The 90% concordance rate with fluorescence in situ hybridization results was achieved by 88% of laboratories for IHC-negative findings and by 81% of laboratories for IHC-positive cases. The 90% concordance rate for laboratories using another IHC assay was achieved by 80% for negative findings and 75% for positive cases. About 91% of laboratories had a pathologist competency assessment program. This survey demonstrates the extent and characteristics of HER2 testing. Although some American Society of Clinical Oncology/College of American Pathologists guidelines have been implemented, gaps remain in validation of HER2 IHC testing.

Whole blood glucose standard is key to accurate insulin dosages.

There is no available glucose standard for whole blood. None of the various glucose controls can be used as standards (calibrators) for glucose meters or test strips. This article describes the need for a whole blood glucose standard for areas such as manufacturing or proficiency evaluations. Furthermore, it describes the performance of the standard developed by Streck. Implementation of a whole blood glucose reference standard may allow the manufacturers of products for the diabetes health care industry to reduce the level of systematic difference between true blood glucose values and those obtained by point-of-care (POC) glucose meters. Glucose agreement data were collected across four prominent POC glucose meters representing >97% of all meters reporting data in the 2006 College of American Pathologists survey. Glucose concentrations of whole blood were adjusted to replicate the concentrations contained in the blood glucose standard developed by Streck. Commercial glucose controls, provided by the respective strip manufacturer, remained unaltered and were tested in accordance with the manufacturer's recommendations. Only slight variations in hematocrit, surface tension, and viscosity were measured over a period of 90 days with the Streck Blood Glucose Standard compared to fresh whole blood at time zero. Glucose measurements on whole blood and the blood glucose standard were in agreement for all four commonly used glucose meters. In contrast, there is a lack of agreement between a manufacturer's set of recommended aqueous-based glucose controls in measurements taken on their POC meter relative to the YSI. Finally, the blood glucose standard demonstrated stability in 35-day open- and 110-day closed-vial assessments. Results of our experiments illustrate the ability of the blood glucose standard to closely mimic whole blood results. In addition, the blood glucose standard shows good open-vial and closed-vial stability at 6 degrees C.

Molecular Diagnostic Testing for Inherited Thrombophilia Using Invader

AbstractFor Abstract see ChemInform Abstract in Full Text.

Variation in the serum creatinine assay calibration: A practical application to glomerular filtration rate estimation

Variation among clinical laboratories in calibration of serum creatinine assays is a source of error in glomerular filtration rate (GFR) estimation equations. We evaluated impact of this variation on GFR estimates. Errors in GFR estimates were computed based on the range of calibration differences from the 1994 College of American Pathologists (CAP) survey using the Modification of Diet in Renal Disease (MDRD) Study GFR equation. Mean (95% CI) calibration difference observed in the CAP survey was +0.14 mg/dL (+12.4 micromol/L) [-0.09, +0.37 mg/dL (-7.96, +32.71 micromol/L)]. Errors in GFR estimates using uncalibrated serum creatinine values were lower in individuals with lower estimated GFR. For GFR of 60 mL/min/1.73 m(2), the mean calibration difference in the CAP survey was associated with errors in GFR estimation between -5.5 to -8.1 mL/min/1.73 m(2) (-9.1 to -13.5%) depending on race and sex. The 95% confidence interval for the calibration difference was associated with a maximal range of error in GFR estimates from +4.6 to -18.1 mL/min/1.73 m(2) (+7.6 to -30.2%). Errors of this magnitude at an estimated GFR of 60 mL/min/1.73 m(2) are not likely to be of clinical significance. However, errors at higher levels of estimated GFR would be greater, making GFR estimates in this range unreliable. Recalibration of serum creatinine assays to the MDRD Study clinical laboratory would improve accuracy of GFR estimation using the MDRD Study equation, but is not practical for all clinical laboratories. As an interim solution, clinical laboratories could report GFR estimates <60 mL/min/1.73 m(2) without recalibration with an acceptable accuracy.

Total long-term within-laboratory precision of cortisol, ferritin, thyroxine, free thyroxine, and thyroid-stimulating hormone assays based on a College of American Pathologists fresh frozen serum study: do available methods meet medical needs for precision?

Abstract 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 compone...