A design for external quality assessment for the analysis of thiopurine drugs: pitfalls and opportunities
-
Karen Robijns
,
Matthijs van Luin
Abstract
Background
For the analysis of 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine ribonucleotides (6-MMPR), no external quality assessment scheme (EQAS) is currently available and no quality control samples can be made because of the absence of pure substances. An experimental design is tested to compare laboratory analytical results.
Methods
In this EQAS, participating laboratories were asked to select patient samples from their routine analysis and exchange these with a coupled laboratory. Because of large differences in results between laboratories, all standard operating procedures were reviewed, revealing that the origin of these differences could be in the method of hydrolysis and the preparation of calibrators. To investigate the contribution of the calibrators to these differences, one participating laboratory was asked to prepare a batch of calibrators to be shipped to the participating laboratories for analysis.
Results
Results for 6-TGN differed more between laboratories, compared with results for 6-MMPR. For 6-TGN and 6-MMPR 43% and 24% of the results, respectively, were out of the 80%–120% range. When correcting the results from the exchange of the patient samples with the results of the calibrators, the mean absolute difference for 6-TGN improved from 24.8% to 16.3% (p<0.001), while the results for 6-MMPR worsened from 17.3% to 20.0% (p=0.020).
Conclusions
This first EQAS for thiopurine drugs shows that there is a difference between laboratories in the analysis of 6-TGN, and to a lesser extent in the analysis of 6-MMPR. This difference for 6-TGN can partially be explained by the use of in-house-prepared calibrators that differ among the participants.
Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: None declared.
Employment or leadership: None declared.
Honorarium: None declared.
Competing interests: The funding organization(s) played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.
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©2018 Walter de Gruyter GmbH, Berlin/Boston
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- On the complexity of hemostasis and the need for harmonization of test practice
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- Harmonization of External Quality Assessment Schemes and their role – clinical chemistry and beyond
- An overview of EFLM harmonization activities in Europe
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- Harmonization of accreditation to ISO15189
- External quality assessment programs in the context of ISO 15189 accreditation
- Section 2: Pre-Pre and Pre-Analytical Phase
- Laboratory testing in the emergency department: an Italian Society of Clinical Biochemistry and Clinical Molecular Biology (SIBioC) and Academy of Emergency Medicine and Care (AcEMC) consensus report
- The EFLM strategy for harmonization of the preanalytical phase
- Section 3: The Analytical Phase
- The roadmap for harmonization: status of the International Consortium for Harmonization of Clinical Laboratory Results
- The quest for equivalence of test results: the pilgrimage of the Dutch Calibration 2.000 program for metrological traceability
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Articles in the same Issue
- Frontmatter
- Editorials
- Harmonization in laboratory medicine: Blowin’ in the wind
- Standardization and harmonization of autoimmune diagnostics
- On the complexity of hemostasis and the need for harmonization of test practice
- Harmonization of laboratory hematology: a long and winding journey
- Section 1: Current Harmonization Activities at Global Level
- Harmonization in laboratory medicine: more than clinical chemistry?
- Harmonization of External Quality Assessment Schemes and their role – clinical chemistry and beyond
- An overview of EFLM harmonization activities in Europe
- Metrological traceability and harmonization of medical tests: a quantum leap forward is needed to keep pace with globalization and stringent IVD-regulations in the 21st century!
- Assessment of bone turnover in osteoporosis: harmonization of the total testing process
- Recent initiatives in harmonization of hemostasis practice
- EASI – European Autoimmunity Standardisation Initiative: facing the challenges of diagnostics in autoimmunity
- Harmonization of microbiology processes and standards: work in progress
- Harmonization initiatives in the generation, reporting and application of biological variation data
- Harmonization of accreditation to ISO15189
- External quality assessment programs in the context of ISO 15189 accreditation
- Section 2: Pre-Pre and Pre-Analytical Phase
- Laboratory testing in the emergency department: an Italian Society of Clinical Biochemistry and Clinical Molecular Biology (SIBioC) and Academy of Emergency Medicine and Care (AcEMC) consensus report
- The EFLM strategy for harmonization of the preanalytical phase
- Section 3: The Analytical Phase
- The roadmap for harmonization: status of the International Consortium for Harmonization of Clinical Laboratory Results
- The quest for equivalence of test results: the pilgrimage of the Dutch Calibration 2.000 program for metrological traceability
- Current state and recommendations for harmonization of serum/plasma 17-hydroxyprogesterone mass spectrometry methods
- International normalized ratio (INR) testing in Europe: between-laboratory comparability of test results obtained by Quick and Owren reagents
- Detecting molecular forms of antithrombin by LC-MRM-MS: defining the measurands
- A design for external quality assessment for the analysis of thiopurine drugs: pitfalls and opportunities
- Harmonization of PCR-based detection of intestinal pathogens: experiences from the Dutch external quality assessment scheme on molecular diagnosis of protozoa in stool samples
- Harmonization of urine albumin/creatinine ratio (ACR) results: a study based on an external quality assessment program in Polish laboratories
- Standardization of autoimmune testing – is it feasible?
- Diagnostic laboratory tests for systemic autoimmune rheumatic diseases: unmet needs towards harmonization
- Clinically relevant discrepancies between different rheumatoid factor assays
- An international survey on anti-neutrophil cytoplasmic antibodies (ANCA) testing in daily clinical practice
- Predictive autoimmunity using autoantibodies: screening for anti-nuclear antibodies
- Harmonization in autoimmune thyroid disease diagnostics
- International consensus on antinuclear antibody patterns: definition of the AC-29 pattern associated with antibodies to DNA topoisomerase I
- Reference standards for the detection of anti-mitochondrial and anti-rods/rings autoantibodies
- International Consensus on Antinuclear Antibody Patterns: defining negative results and reporting unidentified patterns
