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Clin Chim Acta. 2019 Jul 30;498:6-10. doi: 10.1016/j.cca.2019.07.036. [Epub ahead of print]

Commutability of proficiency testing material containing amitriptyline and nortriptyline: A study within the framework of the Dutch Calibration 2.000 project.

Author information

1
Association for Quality Assessment in Therapeutic Drug Monitoring and Clinical Toxicology (KKGT), Section of the Dutch Foundation for Quality Assessment in Medical Laboratories (SKML), The Hague, the Netherlands; Central Hospital Pharmacy, The Hague, the Netherlands; Haga Teaching Hospital, The Hague, the Netherlands; CAPHRI School for Public Health and Primary Care, Maastricht University, Maastricht, the Netherlands; Department of Clinical Pharmacy and Toxicology, Maastricht University Medical Centre+, Maastricht, the Netherlands. Electronic address: k.robijns@ahz.nl.
2
Department of Clinical Pharmacy, Pharmacology and Toxicology, Zuyderland Medical Centre, Sittard-Geleen, the Netherlands.
3
Dutch Foundation for Quality Assessment in Medical Laboratories (SKML), Nijmegen, the Netherlands.
4
Department of Clinical Chemistry and Haematology, Maasziekenhuis Pantein, Beugen, the Netherlands.
5
Association for Quality Assessment in Therapeutic Drug Monitoring and Clinical Toxicology (KKGT), Section of the Dutch Foundation for Quality Assessment in Medical Laboratories (SKML), The Hague, the Netherlands; CAPHRI School for Public Health and Primary Care, Maastricht University, Maastricht, the Netherlands; Department of Clinical Pharmacy and Toxicology, Maastricht University Medical Centre+, Maastricht, the Netherlands.
6
Association for Quality Assessment in Therapeutic Drug Monitoring and Clinical Toxicology (KKGT), Section of the Dutch Foundation for Quality Assessment in Medical Laboratories (SKML), The Hague, the Netherlands; University of Groningen, University Medical Center Groningen, Dept of Clinical Pharmacy and Pharmacology, Groningen, the Netherlands.

Abstract

BACKGROUND:

External quality assessment schemes (EQAS) can provide important information regarding accuracy and comparability of different measurement methods if the sample matrices are composed of commutable material. The aim of this study was to assess the commutability of different matrices for the material used in an EQAS for amitriptyline and nortriptyline.

METHODS:

Proficiency testing material (PTM) and patient samples containing amitriptyline and nortriptyline were prepared, collected, pooled, and distributed to participating laboratories for analysis. Low, medium and high concentrations of both drugs in liquid pooled human, lyophilized human and lyophilized bovine serum were tested in this study. The measurement deviation of the PTM results to the patient serum regression line were normalized by dividing trough the average within-laboratory SD (SDwl) derived from the results reported in the official EQAS, resulting in a relative residual. The commutability decision limit was set at 3 SDwl.

RESULTS:

With 10 laboratories participating in this study, 45 laboratory couples were formed. All matrix types delivered several relative residuals outside the commutability decision limit. The number and the magnitude of relative residuals for both drugs were lower for liquid human sera as compared to lyophilized human and bovine sera.

CONCLUSIONS:

The PTM used for amitriptyline and nortriptyline is preferably prepared with human serum, although not all relative residuals are within the commutability decision limit.

KEYWORDS:

Commutability; External quality assessment scheme; Proficiency testing

PMID:
31374190
DOI:
10.1016/j.cca.2019.07.036

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