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"Laboratory Proficiency Testing"
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Using Aggregated Proficiency Testing Results to Identify Systematic Error
by
Astles, J Rex
,
Kırbıyık, Uzay
in
Binomial distribution
,
Clinical Laboratory Techniques - standards
,
Humans
2025
Abstract
Background
Proficiency testing (PT) should identify systematic errors, which are likely to recur. The Clinical Laboratory Improvement Amendments of 1988 (CLIA) acceptance limits (ALs) include 3 standard deviations (3SD) and concentration limits. We investigated the ability of PT to detect systematic error, especially as affected by the different AL types.
Methods
We removed any ungradable, duplicate, and irregular scores from CLIA laboratory PT data from 2008 to 2018. We calculated the overall miss rate, unsatisfactory event rate, i.e., score <80 (4 of 5 correct), and event rates for score 100 to 0. We used paired t-tests and the Wilcoxon signed-rank test to compare miss rates and unsatisfactory event rates between short- and long-term PT participants. We used the binomial distribution to estimate the expected event scores under the assumption that all misses were independent (random). We compared observed event scores with their expected values as a ratio.
Results
Forty thousand five hundred ninety-six laboratories produced 15 140 128 event scores for 75 analytes. The distribution of event scores was skewed toward multiple event misses (score 0–60) compared to the predicted distribution. Miss rates and unsatisfactory rates were significantly higher for short-term laboratories. Plotting the log ratio of observed vs expected rates for event scores showed that the degree of systematic effect was substantial. The magnitude of the effect was less for 3SD ALs.
Conclusions
In an event, PT misses are often dependent. All ALs detected systematic error. Expressing systematic error using PT data could help to identify and remediate analytical issues.
Journal Article
Towards harmonization of microscopy methods for malaria clinical research studies
by
Lilley, Ken
,
Proux, Stéphane
,
Ogutu, Bernhards
in
Biomedical and Life Sciences
,
Biomedicine
,
Blood
2020
Microscopy performed on stained films of peripheral blood for detection, identification and quantification of malaria parasites is an essential reference standard for clinical trials of drugs, vaccines and diagnostic tests for malaria. The value of data from such research is greatly enhanced if this reference standard is consistent across time and geography. Adherence to common standards and practices is a prerequisite to achieve this. The rationale for proposed research standards and procedures for the preparation, staining and microscopic examination of blood films for malaria parasites is presented here with the aim of improving the consistency and reliability of malaria microscopy performed in such studies. These standards constitute the core of a quality management system for clinical research studies employing microscopy as a reference standard. They can be used as the basis for the design of training and proficiency testing programmes as well as for procedures and quality assurance of malaria microscopy in clinical research.
Journal Article
Seven Q-Tracks Monitors of Laboratory Quality Drive General Performance Improvement: Experience From the College of American Pathologists Q-Tracks Program 1999–2011
by
Jones, Bruce A.
,
Howanitz, Peter J.
,
Karcher, Donald S.
in
Clinical Laboratory Techniques - methods
,
Clinical Laboratory Techniques - standards
,
Humans
2015
Many production systems employ standardized statistical monitors that measure defect rates and cycle times, as indices of performance quality. Clinical laboratory testing, a system that produces test results, is amenable to such monitoring.
To demonstrate patterns in clinical laboratory testing defect rates and cycle time using 7 College of American Pathologists Q-Tracks program monitors.
Subscribers measured monthly rates of outpatient order-entry errors, identification band defects, and specimen rejections; median troponin order-to-report cycle times and rates of STAT test receipt-to-report turnaround time outliers; and critical values reporting event defects, and corrected reports. From these submissions Q-Tracks program staff produced quarterly and annual reports. These charted each subscriber's performance relative to other participating laboratories and aggregate and subgroup performance over time, dividing participants into best and median performers and performers with the most room to improve. Each monitor's patterns of change present percentile distributions of subscribers' performance in relation to monitoring durations and numbers of participating subscribers. Changes over time in defect frequencies and the cycle duration quantify effects on performance of monitor participation.
All monitors showed significant decreases in defect rates as the 7 monitors ran variously for 6, 6, 7, 11, 12, 13, and 13 years. The most striking decreases occurred among performers who initially had the most room to improve and among subscribers who participated the longest. All 7 monitors registered significant improvement. Participation effects improved between 0.85% and 5.1% per quarter of participation.
Using statistical quality measures, collecting data monthly, and receiving reports quarterly and yearly, subscribers to a comparative monitoring program documented significant decreases in defect rates and shortening of a cycle time for 6 to 13 years in all 7 ongoing clinical laboratory quality monitors.
Journal Article
Feasibility and potential impact of a local proficiency testing program in Accra, Ghana
by
Ahmad, Yembur
,
Sarpong, Kwabena A N
,
Bansah, Lois Y
in
Accreditation
,
Feasibility Studies
,
Ghana
2025
To implement a pilot proficiency testing (PT) program in Accra, Ghana, using locally produced PT materials and to explore the relationship between laboratory test costs and laboratory quality in Accra, Ghana.
Remnant serum samples from a local laboratory were pooled, aliquoted, and distributed to a convenience sample of 23 laboratories in Accra, Ghana, 2 of which had International Organization for Standardization (ISO) accreditation. One of the ISO-accredited laboratories was designated as the reference/target, and the range for passing was based on international criteria. Test cost, test results, and testing instruments used were compiled.
Of the 23 laboratories, 18 submitted results. Total testing costs ranged from 80 to 312 Ghanaian cedi (GH₵) (7-26 USD). Overall accuracy (pass rate) was calculated per laboratory and per analyte. The mean laboratory accuracy was 61% (15%-92%). The pass rate for individual analytes ranged from 18% to 94% (mean, 72%). There was no correlation between test cost and pass rate.
The pass rates of clinical laboratories in Accra, Ghana, varied from 15% to 92%, and there was no relationship to test cost. A PT program to objectively evaluate each laboratory's performance is needed. Making the PT material locally, as in this study, is a financially sustainable approach.
Journal Article
State of Affairs of Tuberculosis in Prison Facilities: A Systematic Review of Screening Practices and Recommendations for Best TB Control
by
van Elsland, Sabine L.
,
Lange, Joep M. A.
,
Vinkeles Melchers, Natalie V. S.
in
Algorithms
,
Analysis
,
Cough
2013
Prisoners are at high risk of developing tuberculosis (TB), causing morbidity and mortality. Prison facilities encounter many challenges in TB screening procedures and TB control. This review explores screening practices for detection of TB and describes limitations of TB control in prison facilities worldwide.
A systematic search of online databases (e.g., PubMed and Embase) and conference abstracts was carried out. Research papers describing screening and diagnostic practices among prisoners were included. A total of 52 articles met the inclusion criteria. A meta-analysis of TB prevalence in prison facilities by screening and diagnostic tools was performed.
The most common screening tool was symptom questionnaires (63·5%), mostly reporting presence of cough. Microscopy of sputum with Ziehl-Neelsen staining and solid culture were the most frequently combined diagnostic methods (21·2%). Chest X-ray and tuberculin skin tests were used by 73·1% and 50%, respectively, as either a screening and/or diagnostic tool. Median TB prevalence among prisoners of all included studies was 1,913 cases of TB per 100,000 prisoners (interquartile range [IQR]: 332-3,517). The overall annual median TB incidence was 7·0 cases per 1000 person-years (IQR: 2·7-30·0). Major limitations for successful TB control were inaccuracy of diagnostic algorithms and the lack of adequate laboratory facilities reported by 61·5% of studies. The most frequent recommendation for improving TB control and case detection was to increase screening frequency (73·1%).
TB screening algorithms differ by income area and should be adapted to local contexts. In order to control TB, prison facilities must improve laboratory capacity and frequent use of effective screening and diagnostic tools. Sustainable political will and funding are critical to achieve this.
Journal Article
Test Cost and Test Accuracy in Clinical Laboratories in Kampala, Uganda
2018
Abstract
Objectives
To assess the accuracy and costs of laboratory tests in Kampala, Uganda.
Methods
A random selection of 78 laboratories tested external quality assurance samples at market rates. There were 40 moderate- to high-complexity and 38 low-complexity laboratories. Four percent (3/78) of these laboratories were accredited and 94% (73/78) were private. The 40 moderate- to high-complexity laboratories performed malaria blood smear, urine human chorionic gonadotropin (hCG), human immunodeficiency virus (HIV), syphilis, glucose, and three-panel tests: CBC, liver function tests, and kidney function tests. The 38 low-complexity laboratories performed malaria blood smear, urine hCG, and syphilis testing only. Hematology, HIV, syphilis, and malarial proficiency testing samples were prepared by accredited laboratories in Kampala. All other samples were provided by the Royal College of Pathologists of Australia.
Results
77.1% of all results were accurate (met target values). It varied widely by laboratory (50%-100%), test identity (malaria blood smear, 96%; serum urea nitrogen, 38%), and test type (quantitative: 66% [31%-89%], qualitative: 91% [68%-97%]). Test prices varied by up to 3,600%, and there was no correlation between test cost and accuracy (r2 = 0.02).
Conclusions
There were large differences in accuracy and price across laboratories in Kampala. Price was not associated with quality.
Journal Article
CAP/ACMG proficiency testing for biochemical genetics laboratories: a summary of performance
by
Wood, Timothy C.
,
Pasquali, Marzia
,
Weck, Karen E.
in
631/208/1516
,
631/208/2489/1512
,
692/699/317
2018
Testing for inborn errors of metabolism is performed by clinical laboratories worldwide, each utilizing laboratory-developed procedures. We sought to summarize performance in the College of American Pathologists’ (CAP) proficiency testing (PT) program and identify opportunities for improving laboratory quality. When evaluating PT data, we focused on a subset of laboratories that have participated in at least one survey since 2010.
An analysis of laboratory performance (2004 to 2014) on the Biochemical Genetics PT Surveys, a program administered by CAP and the American College of Medical Genetics and Genomics. Analytical and interpretive performance was evaluated for four tests: amino acids, organic acids, acylcarnitines, and mucopolysaccharides.
Since 2010, 150 laboratories have participated in at least one of four PT surveys. Analytic sensitivities ranged from 88.2 to 93.4%, while clinical sensitivities ranged from 82.4 to 91.0%. Performance was higher for US participants and for more recent challenges. Performance was lower for challenges with subtle findings or complex analytical patterns.
US clinical biochemical genetics laboratory proficiency is satisfactory, with a minority of laboratories accounting for the majority of errors. Our findings underscore the complex nature of clinical biochemical genetics testing and highlight the necessity of continuous quality management.
Journal Article
Prevalence of Traditional and Reverse-Algorithm Syphilis Screening in Laboratory Practice: A Survey of Participants in the College of American Pathologists Syphilis Serology Proficiency Testing Program
by
Bashleben, Christine P.
,
Rhoads, Daniel D.
,
Ansari, M. Qasim
in
Algorithms
,
American Medical Association
,
Diagnosis
2017
Context.— Syphilis serology screening in laboratory practice is evolving. Traditionally, the syphilis screening algorithm begins with a nontreponemal immunoassay, which is manually performed by a laboratory technologist. In contrast, the reverse algorithm begins with a treponemal immunoassay, which can be automated. The Centers for Disease Control and Prevention has recognized both approaches, but little is known about the current state of laboratory practice, which could impact test utilization and interpretation. Objective.— To assess the current state of laboratory practice for syphilis serologic screening. Design.— In August 2015, a voluntary questionnaire was sent to the 2360 laboratories that subscribe to the College of American Pathologists syphilis serology proficiency survey. Results.— Of the laboratories surveyed, 98% (2316 of 2360) returned the questionnaire, and about 83% (1911 of 2316) responded to at least some questions. Twenty-eight percent (378 of 1364) reported revision of their syphilis screening algorithm within the past 2 years, and 9% (170 of 1905) of laboratories anticipated changing their screening algorithm in the coming year. Sixty-three percent (1205 of 1911) reported using the traditional algorithm, 16% (304 of 1911) reported using the reverse algorithm, and 2.5% (47 of 1911) reported using both algorithms, whereas 9% (169 of 1911) reported not performing a reflex confirmation test. Of those performing the reverse algorithm, 74% (282 of 380) implemented a new testing platform when introducing the new algorithm. Conclusion.— The majority of laboratories still perform the traditional algorithm, but a significant minority have implemented the reverse-screening algorithm. Although the nontreponemal immunologic response typically wanes after cure and becomes undetectable, treponemal immunoassays typically remain positive for life, and it is important for laboratorians and clinicians to consider these assay differences when implementing, using, and interpreting serologic syphilis screening algorithms.
Journal Article
Marked Variability in Reported Minimal Residual Disease Lower Level of Detection of 4 Hematolymphoid Neoplasms: A Survey of Participants in the College of American Pathologists Flow Cytometry Proficiency Testing Program
by
Linden, Michael A.
,
Keeney, Michael
,
Karlon, William J.
in
Flow Cytometry - methods
,
Flow Cytometry - standards
,
Humans
2015
Flow cytometry is often applied to minimal residual disease (MRD) testing in hematolymphoid neoplasia. Because flow-based MRD tests are developed in the laboratory, testing methodologies and lower levels of detection (LODs) are laboratory dependent.
To broadly survey flow cytometry laboratories about MRD testing in laboratories, if performed, including indications and reported LODs.
Voluntary supplemental questions were sent to the 549 laboratories participating in the College of American Pathologists (CAP) FL3-A Survey (Flow Cytometry-Immunophenotypic Characterization of Leukemia/Lymphoma) in the spring of 2014.
A total of 500 laboratories (91%) responded to the supplemental questions as part of the FL3-A Survey by April 2014; of those 500 laboratories, 167 (33%) currently perform MRD for lymphoblastic leukemia, 118 (24%) for myeloid leukemia, 99 (20%) for chronic lymphocytic leukemia, and 91 (18%) for plasma cell myeloma. Other indications include non-Hodgkin lymphoma, hairy cell leukemia, neuroblastoma, and myelodysplastic syndrome. Most responding laboratories that perform MRD for lymphoblastic leukemia reported an LOD of 0.01%. For myeloid leukemia, chronic lymphocytic leukemia, and plasma cell myeloma, most laboratories indicated an LOD of 0.1%. Less than 3% (15 of 500) of laboratories reported LODs of 0.001% for one or more MRD assays performed.
There is major heterogeneity in the reported LODs of MRD testing performed by laboratories subscribing to the CAP FL3-A Survey. To address that heterogeneity, changes to the Flow Cytometry Checklist for the CAP Laboratory Accreditation Program are suggested that will include new requirements that each laboratory (1) document how an MRD assay's LOD is measured, and (2) include the LOD or lower limit of enumeration for flow-based MRD assays in the final diagnostic report.
Journal Article
Results of the UK NEQAS for Molecular Genetics reference sample analysis
by
Norman, Kara L
,
Nataraj, Nakul
,
Hall, Jacqueline A
in
Biomarkers, Tumor - genetics
,
Cell Line
,
Colorectal cancer
2018
AimsIn addition to providing external quality assessment (EQA) schemes, United Kingdom National External Quality Assessment service (UK NEQAS) for Molecular Genetics also supports the education of laboratories. As an enhancement to the Molecular Pathology EQA scheme, a human cell-line reference sample, manufactured by Thermo Fisher Scientific (AcroMetrix), was provided for analysis. This contained many variants, present at frequencies between 1% and 17.9%.MethodsOne hundred and one laboratories submitted results, with a total of 2889 test results on 53 genes being reported. Known polymorphisms, 46/2889 (1.59%) results, were excluded. Variants detected in the seven most commonly reported (and clinically relevant) genes, KRAS, NRAS, BRAF, EGFR, PIK3CA, KIT and PDGFRA, are reported here, as these genes fall within the scope of UK NEQAS EQA schemes.ResultsNext generation sequencing (NGS) was the most commonly performed testing platform. There were between 5 and 27 validated variants in the seven genes reported here. Eight laboratories correctly reported all five NRAS variants, and two correctly reported all eight BRAF variants. The validated mean variant frequency was lower than that determined by participating laboratories, with single-gene testing methodologies showing less variation in estimated frequencies than NGS platforms. Laboratories were more likely to correctly identify clinically relevant variants.ConclusionsOver 100 laboratories took the opportunity to test the ‘educational reference sample’, showing a willingness to further validate their testing platforms. While it was encouraging to see that the most widely reported variants were those which should be included in routine testing panels, reporting of variants was potentially open to interpretation, thus clarity is still required on whether laboratories selectively reported variants, by either clinical relevance or variant frequency.
Journal Article