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

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.

Commutability of proficiency testing material containing tobramycin: a study within the framework of the Dutch Calibration 2.000 project.

Background: Results from external quality assessment schemes (EQASs) can provide information about accuracy and comparability of different measurement methods, provided that the material used in these schemes behave identical to patient samples among the different methods, a characteristic also known as commutability. The aim of this study was to assess the commutability of different matrices for the material used in an EQAS for tobramycin.

Methods: Proficiency testing material (PTM) and patient samples containing tobramycin were prepared, collected, pooled, and distributed to participating laboratories for analysis.

A Multilaboratory Commutability Evaluation of Proficiency Testing Material for Carbamazepine and Valproic Acid: A Study Within the Framework of the Dutch Calibration 2000 Project.

Background: Medical laboratories are required to participate in interlaboratory comparisons of the analyses they perform. The materials used in these comparisons need to be of sufficient quality so that the comparison provides a picture of the performances. One of the main characteristics of the testing material is commutability, which is the ability of a material to yield the same numerical relationships between results of measurements as those relationships obtained when the same procedures are applied to patient samples.