External Quality Assurance Surveys Research Articles

Improving the Diagnosis, Treatment, and Prevention of Endocrine Diseases Through Accurate and Reliable Laboratory Measurements With CDC Clinical Standardization Programs

Laboratory measurements are critical for correct diagnosis and treatment of patients with chronic diseases such as hypogonadism, PCOS, and thyroid diseases. Inaccurate measurements of disease biomarkers can lead to misclassification of patients/incorrect treatment and prevent the effective use of research findings in patient care. The CDC Clinical Standardization Programs (CDC CSP) improve the accuracy and reliability of clinical biomarker measurements by assessing and improving the analytical performance of assays. The CDC CSP assist with assay calibration, the certification of analytical performance, and the monitoring of routine patient and research testing. The CDC CSP work with clinical/research laboratories and assay manufacturers to improve laboratory measurements. Its current programs include the following analytes: total testosterone (TT), estradiol (E2), vitamin D (VD), free thyroxine (FT4), total cholesterol (TC), total glycerides (TG), HDL-cholesterol (HDL-C), and LDL-cholesterol (LDL-C). The work is being conducted through certification/monitoring programs and technical assistance. Most assays participating in the certification programs have seen performance improvements and maintain performance over time by continuous participation. Most major commercial laboratories and assays manufactures are enrolled in the certification programs. Currently certified and non-certified assays are available. Assays certified by CDC CSP are listed on the website at https://www.cdc.gov/labstandards/hs.html. The CDC Lipid Standardization Programs and CDC Accuracy-based Monitoring Programs allow for weekly monitoring of analytical performance of routine tests for analytes including TT, VD, TC, TG, HDL-C, apolipoprotein A1 and B. These monitoring programs assist researchers with assessing measurement accuracy of research studies over time and across laboratories. The CDC CSP also support accuracy-based external quality assurance surveys such as those offered by the College of American Pathologists (CAP). The CDC CSP assist researchers and stakeholders with developing and establishing reference intervals and conducting studies to better assess and diagnose patients. Based on the needs and requests from clinical community, programs for new biomarkers such as Lp(a), PTH and glucose are being developed. The CDC CSP work with stakeholders, such as the Endocrine Society and the Partnership for the Accurate Testing of Hormones, to educate the clinical and laboratory communities about the importance of using standardized assays in patient care, research, and public health.

SAT-733 Improving the Diagnosis, Treatment, and Prevention of Endocrine Diseases Through Accurate and Reliable Laboratory Measurements with CDC’s Clinical Standardization Programs

Laboratory measurements are critical for the correct diagnosis and treatment of patients as well as in the investigation of chronic diseases such as hypogonadism, PCOS, and bone-and kidney-related diseases. Inaccurate measurements can lead to misclassification of patients and incorrect treatment. Furthermore, the effective use of research findings in patient care is prevented. The CDC Clinical Standardization Programs (CDC CSP) assess the analytical performance of assays against performance goals defined by clinical and medical organizations. The CDC CSP assist with assay calibration, the certification of analytical performance, and the monitoring of analytical performance during the measurement of patient and/or study samples. CDC CSP have programs in place for the calibration and certification of commercial assays and laboratory developed tests (LDTs) for total testosterone (TT), estradiol (E2), vitamin D (VD), free thyroxine (FT4), total cholesterol (TC), total glycerides (TG), HDL-cholesterol (HDL-C), and LDL-cholesterol (LDL-C). The programs available for monitoring analytical performance during routine testing include TT, VD, TC, TG, HDL-C, apolipoprotein AI and B. CDC CSP also support accuracy-based external quality assurance surveys such as those offered by the College of American Pathologists. Enrollment of assays and LDTs in CDC’s certification programs has resulted in improvements in calibration accuracy; i.e. the absolute mean bias of assays participating in the CDC Vitamin D Standardization Certification Program was well below the allowable bias of 5% each year. Assays standardized in CDC’s certification programs also demonstrated higher accuracy in routine patient testing; i.e. CDC VD certified assays have a lower bias compared to non-certified assays. Similar observations were made with assays certified in the CDC’s program for TT. Monitoring data over the past 10 years from the CDC Lipid Standardization Program indicated that the majority of TC measurements performed in routine testing were consistently within the recommended bias limits of ±3%. CDC CSP continue to improve the analytical performance of assays by addressing measurement bias caused by factors other than incorrect calibration such as interfering compounds. The programs are responding to new clinical and public health needs with the addition of new analytes such as PTH and glucose. The CDC CSP support projects aiming at establishing reference intervals and other research studies. The CDC CSP work with stakeholders, such as the Partnership for the Accurate Testing of Hormones and the Endocrine Society, to educate the clinical and laboratory communities about the importance of using standardized assays in patient care, research, and public health.

Availability and analytical quality of hemoglobin A1c point-of-care testing in general practitioners' offices are associated with better glycemic control in type 2 diabetes.

Background It is not clear if point-of-care (POC) testing for hemoglobin A1c (HbA1c) is associated with glycemic control in type 2 diabetes. Methods In this cross-sectional study, we linked general practitioner (GP) data on 22,778 Norwegian type 2 diabetes patients to data from the Norwegian Organization for Quality Improvement of Laboratory Examinations. We used general and generalized linear mixed models to investigate if GP offices' availability (yes/no) and analytical quality of HbA1c POC testing (average yearly "trueness score", 0-4), as well as frequency of participation in HbA1c external quality assurance (EQA) surveys, were associated with patients' HbA1c levels during 2014-2017. Results Twenty-eight out of 393 GP offices (7%) did not perform HbA1c POC testing. After adjusting for confounders, their patients had on average 0.15% higher HbA1c levels (95% confidence interval (0.04-0.27) (1.7 mmol/mol [0.5-2.9]). GP offices participating in one or two yearly HbA1c EQA surveys, rather than the maximum of four, had patients with on average 0.17% higher HbA1c levels (0.06, 0.28) (1.8 mmol/mol [0.6, 3.1]). For each unit increase in the GP offices' HbA1c POC analytical trueness score, the patients' HbA1c levels were lower by 0.04% HbA1c (-0.09, -0.001) (-0.5 mmol/mol [-1.0, -0.01]). Conclusions Novel use of validated patient data in combination with laboratory EQA data showed that patients consulting GPs in offices that perform HbA1c POC testing, participate in HbA1c EQA surveys, and maintain good analytical quality have lower HbA1c levels. Accurate HbA1c POC results, available during consultations, may improve diabetes care.

Analysis of a 6-year pilot external quality assurance survey of free light chain using Sigma metrics

AbstractBackgroundA pilot external quality assurance (EQA) survey for the free light chain (FLC) assay was developed and implemented in Korea.MethodsSurvey data over 6 years (2010–2015) were collected retrospectively and Sigma metrics were calculated for method-specific peer groups.ResultsNineteen to 29 laboratories participated in the EQA survey, and nephelometric (20%) and turbidimetric (80%) methods were used. Using a previously published clinically relevant reference change value (RCV) of 54.5% as the tolerance limit, the method-specific median Sigma metrics of kappa (κ) and lambda (λ) FLC achieved greater than Three-Sigma for 86–97% of all EQA distributions, and Five-Sigma for 48–72% of all distributions.ConclusionsThis EQA analysis of FLC assay applied clinically relevant quality specifications using Sigma metrics. During the 6-year EQA survey, we found that most of the results from participating laboratories meet clinically relevant quality specifications. In addition, method-specific differences were noted for λ FLC, at FLC concentrations above the initial measuring range that require a sample dilution.

Preclinical evaluation of a semi-automated and rapid commercial electrophoresis assay for von Willebrand factor multimers.

The von Willebrand factor (VWF) multimer test is required to correctly subtype qualitative type 2 von Willebrand disease (VWD). The current VWF multimer assays are difficult, nonstandardized, and time-consuming. The purpose of this study was to evaluate the clinical utility of the commercial VWF multimer kit by Sebia (Lisses, France), an electrophoresis technique yielding same-day results. Ten healthy volunteer plasma samples, in-house reference plasma (IRP) and commercial normal plasma (CNP) samples, 10 plasma samples from patients with a known VWD type, 1 hemophilia A plasma sample, and 7 external quality assurance (EQA) samples were analyzed using the commercial VWF multimer kit. Additional coagulation testing included measurements of VWF antigen (VWF:Ag), VWF activity (VWF:Ac), and FVIII activity (FVIII:C). The CNP results revealed a relative loss of the highest molecular weight multimers; therefore, IRP was preferred as the reference sample. The interpretations of 10 patients with a known VWD type could be successfully reproduced and agreed with previous VWF multimer results. In all EQA surveys, the multimer results and final VWD diagnosis agreed with expert opinion. The VWF multimer assay by Sebia is easy to perform and can be successfully implemented in any clinical laboratory for second-stage evaluation of VWD. The resolution power of multimer distribution is adequate to correctly classify VWD types 1, 2A, 2B, and 3.

Analytical performance evaluation of a high-volume hematology laboratory utilizing sigma metrics as standard of excellence.

Around two-thirds of important clinical decisions about the management of patients are based on laboratory test results. Clinical laboratories are required to adopt quality control (QC) measures to ensure provision of accurate and precise results. Six sigma is a statistical tool, which provides opportunity to assess performance at the highest level of excellence. The purpose of this study was to assess performance of our hematological parameters on sigma scale in order to identify gaps and hence areas of improvement in patient care. Twelve analytes included in the study were hemoglobin (Hb), hematocrit (Hct), red blood cell count (RBC), mean corpuscular volume (MCV), red cell distribution width (RDW), total leukocyte count (TLC) with percentages of neutrophils (Neutr%) and lymphocytes (Lymph %), platelet count (Plt), mean platelet volume (MPV), prothrombin time (PT), and fibrinogen (Fbg). Internal quality control data and external quality assurance survey results were utilized for the calculation of sigma metrics for each analyte. Acceptable sigma value of ≥3 was obtained for the majority of the analytes included in the analysis. MCV, Plt, and Fbg achieved value of <3 for level 1 (low abnormal) control. PT performed poorly on both level 1 and 2 controls with sigma value of <3. Despite acceptable conventional QC tools, application of sigma metrics can identify analytical deficits and hence prospects for the improvement in clinical laboratories.

Diagnosing Diabetes Mellitus: Performance of Hemoglobin A1c Point-of-Care Instruments in General Practice Offices

Hemoglobin A1c (Hb A1c) measurement by hospital laboratory instruments, but not by point-of-care (POC) instruments, has been recommended for use to diagnose diabetes mellitus. We evaluated results from 13 Hb A1c external quality assurance (EQA) surveys over a 6-year period in Norway, from both POC instruments used in general practice (GP) offices and instruments in hospital laboratories, against the analytical quality specifications recommended for use of Hb A1c to diagnose diabetes mellitus. All GP offices (n = 1288) and hospital laboratories (n = 52) measuring Hb A1c in Norway participated in the EQA survey. The percentage of participants that performed measurements within the quality specifications was calculated. Pooled within-laboratory CVs were estimated for the Afinion, DCA 2000, DCA 2000+, DCA Vantage(TM), and Nycocard Hb A1c Reader instruments and for hospital laboratory instruments. Between 60% to 90% of Afinion and DCA users and hospital laboratories performed Hb A1c measurements within the quality specifications for both trueness (6.0%) and imprecision (CV ≤2.0%) at 2 levels in each EQA survey. The pooled within-laboratory CVs for the Afinion and DCA instruments and hospital laboratories were below the recommended limit of 2.0% for most of the surveys. A large proportion of GP offices using Afinion and DCA POC instruments to measure Hb A1c fulfill the analytical quality specifications for diagnosing diabetes mellitus, and these instruments demonstrate analytical quality comparable to that of hospital laboratory instruments. When GP offices participate in a stringent quality assurance program and generate Hb A1c measurements that meet analytical quality specifications, these measurements can be recommended for use to diagnose diabetes mellitus.

Measurement of Lupus Anticoagulants: An Update on Quality in Laboratory Testing

Lupus anticoagulants (LAs) are antiphospholipid antibodies that interfere with in vitro phospholipid-dependent clotting tests, but are associated in vivo with significant clinical manifestations such as recurrent pregnancy loss and venous and arterial thrombosis. Although their detection is important for the diagnosis of thrombotic disorders such as the antiphospholipid syndrome, laboratory identification has historically been fraught with many issues. These have included variability in the sensitivity of assays and reagents; high false-negative and false-positive detection rates; a lack of consensus for the use of mixing tests; and, to some extent, lack of compliance with guidelines published by the Lupus Anticoagulant/Antiphospholipid Antibody Scientific Standardization Committee of the International Society on Thrombosis and Haemostasis (ISTH). Since the most recently updated guidelines in 2009, external quality assurance (EQA) programs have conducted surveys to provide a "snapshot" of laboratory practices related to the investigation of LA and to identify problems and monitor improvements in testing for LA. This article will review the impact of the most recently updated ISTH guidelines for LA testing and discuss the findings of recent EQA surveys.

2B or not 2B? Disparate discrimination of functional VWF discordance using different assay panels or methodologies may lead to success or failure in the early identification of type 2B VWD

Laboratory proficiency in the identification of functional von Willebrand factor (VWF) discordance in type 2B von Willebrand disease (VWD) was assessed by external quality assurance surveys conducted by the RCPA Haematology QAP, and using six different type 2B VWD plasma samples (three historical and three previously unpublished) tested by up to 52 laboratories. For the three most recent samples, functional VWF discordance was either not identified in testing or by interpretation with misidentification as 'normal' or 'type 1 VWD', on average for 25.7% of test occasions when laboratories performed VWF:Ag and VWF:RCo as their primary VWF test panel, but somewhat fewer occasions (10.9%) for laboratories that incorporated VWF:CB as an additional functional VWF assay. VWF assay sub-methodologies also influenced the appropriate identification of samples as potentially type 2 VWD, and VWF functional discordance was more consistently identified when laboratories used (i) automated platelet agglutination for VWF:RCo compared to classical platelet aggregometry, (ii) inhouse VWF:CB assays compared to commercial kit methods, and (iii) automated LIA-based 'VWF:Activity' assays compared to ELISA based assays. We conclude that:(i) laboratories are generally proficient in tests for VWD but interpretative diagnostic errors do occur; (ii) correct diagnosis is more likely when test panels are more comprehensive and include the VWF:CB; (iii) sub-methodology influences the appropriate identification of VWF functional discordance. On the basis of these findings, we provide a series of recommendations to enable the appropriate laboratory identification of VWD, in particular type 2B VWD.

Estimation of the biological variation of glucose-6-phosphate dehydrogenase in dried blood spots

Models based on biological variation provide a well-accepted database with reliable information for clinical laboratories for all purposes including screening, diagnosis and follow-up. Newborn screening laboratories use a blood spotted paper matrix to measure the analytes. This matrix medium is certainly different than body fluid matrix medium. After long-term monitoring of the performance of the Glucose-6-Phosphate Dehydrogenase Kit (R&D Diagnostics OSMMR 2000-D G6PD), the results obtained from the variation analysis were statistically evaluated. Analytical coefficient of variation, CVA, was found to be 5.41%. The CVA derived from between run assays was 5.32%, while within-subject biological coefficient of variation, CVI, was 7.26%. Since minimum performance is defined as CVA< 0.750 CVI, CVA should be lower than 5.44%. The analytical bias in calculation of total error \(B_{\rm A} < 0.375\break \sqrt {\left( {\it CV_{\rm I}} \right)^2 + \left( {\it CV_{\rm G}} \right)^2}\) was chosen to evaluate the performance of this assay. In this aspect, CVG, between-subject biological coefficient of variation, was found to be equal to 10.35%. BA was found to be 4.12%, which is lower than 4.74%, which means that it is acceptable. Therefore, the minimum quality specification for total error allowable is \({\it TE}_{\rm a} < 1.65(0.75\,CV_{\rm I} ) + {\rm }0.375\sqrt {\left( {\rm CV_{\rm I}} \right)^2 + \left( {\rm CV_{\rm G}} \right)^2 }\) . When the relevant results obtained in this study were substituted in this formula, TEa was found to be 13.7% for G6PD measurement in dried blood spots on paper filter matrix. It is expected that this figure will be helpful for the performance evaluation of newborn screening laboratories performing G6PD screening. We have been using error grid graphs for the evaluation of our external quality assurance survey results for the last two years, only because there was no data for assays employing filter matrix. Even the TEa already reported for EDTA whole blood samples used in G6PD assays has been remarkably high, which can easily create the wrong impression that G6PD is not a reliable test to perform from blood spot cards. The present study shows that this assay is adequately reliable even when performed from dried blood spot matrix. However, we believe that the combination of total allowable error, error grid graphs with a well-defined cut off is the best approach to obtain an accurate performance evaluation for this test.

Problematic determination of serum growth hormone: Experience from external quality assurance surveys 1998–2003

The objective of the present study was to start a new external quality assurance survey (EQAS) for the determination of serum growth hormone (GH) using pooled serum specimens as quality‐assurance samples. To give good coverage of multiple forms of GH, the specimens included sera from GH‐deficient and acromegalic patients as well as from persons showing a normal response in GH provocation tests. In one survey the quality‐control specimens were spiked with exogenous 22‐kD GH to obtain some idea of the specificity and GH recovery of the assays. The EQA surveys of 1998–2003 were organized by Labquality of Helsinki in cooperation with three university hospital laboratories in Finland. The number of participating laboratories ranged from 8 to 14. During 1998–2003, gratifying methodological harmonization occurred in the participating group, as the participants switched to the immunometric detection principle, the number of method applications decreasing from 7 to 3. In 1998 the 14 participating laboratories reported five different conversion factors (from µg/l to mU/l), whereas in 2003 7 of the 8 participants reported the same factor. Despite the harmonization trend among participating laboratories, further efforts are needed, because marked method‐based differences still exist. This dialogue should include kit manufacturers, laboratory experts, EQA organizations and clinicians using the test results.

Interference of dextran in biuret-type assays of serum proteins

Dextran interference in biuret-type assays of total serum proteins was investigated in a Belgian National External Quality Assurance Survey with 256 participants. In vitro supplementation of therapeutic (10% Gentran 70) dextran concentrations showed a broadly varying (from 0 to 20%) negative interference. The analytical interference was found to depend on both the sodium hydroxide and tartrate concentrations in the reagent formulation. The dry chemistry biuret method was not affected by the dextran interference. In a number of cases, the effects observed may be of clinical importance. Both clinicians and laboratory staff should be aware of the persistence of this analytical problem.