Application of secondary pH measurement method for homogeneity and stability assessment of reference materials

In this work, the development and optimization of a secondary method for pH measurement using a differential potentiometric cell are described. The method was optimized and validated by measurement of three certified primary buffer solutions (CRMs) with nominal pH values of 4.005, 6.865 and 9.180 at 25 °C. The method was applied to assess homogeneity and stability of phosphate buffer solution with nominal pH of 7.000 at 25 °C which will be used as test item in proficiency testing schemes for pH measurement of testing laboratories. The experiments carried out and described in this article proved that this particular design of secondary differential potentiometric cell requires small volume of solutions, is fast, accurate and precise and is suitable for the characterization of secondary buffer solutions and assessment of homogeneity and stability of buffer solutions.

Features of the Functioning of the National Metrological System in the Health Sector

The legislative requirements for metrological support in the healthcare sector, the issues of ensuring metrological traceability and the hierarchical scheme of calibrations and measurements in laboratory medicine according to the recommendations of JCTLM and their adaptation at the national level are considered. The features of the provided metrological control of measuring instruments for medical purposes, including when conducting their compliance assessment with the requirements of technical regulations. The current state of affairs in the confirmation of the technical competence of medical laboratories, including the need for their participation in proficiency testing schemes through inter-laboratory comparisons, in the transition from certification to accreditation is considered. The analysis of the used methods and means of calibration and reference measurements proposed by JCTLM and other leading orga­nizations in the field of laboratory medicine is observed. Information is provided on the work carried out by the SE «Ukrmetrteststandart» for metrological support of medical measuring instruments. The necessity of legal improvement, the regulatory and methodological base of the metrological system in the field of healthcare is substantiated. As a result of the work performed, the authors consider: the legislative base of metrological support in the field of healthcare is not perfect and in need of refinement of the profile of the central executive authorities in order to build technically sound organizational and regulatory frameworks for metrological support in this area; proficiency testing through interlaboratory comparisons in the field of laboratory medicine is an effective tool for confirming the technical competence of the laboratory. Laboratories should parti­cipate in proficiency testing schemes on a regular basis. Proficiency testing providers should pay particular attention to the method of determining reference values of indicators in proficiency testing samples, using predominantly metrologically sound procedures based on the use of standards, certified reference materials and/or reference measurement methods; the heads of medical laboratories should be careful about the choice of suppliers of legal acts in the metrology.

Selecting proficiency testing schemes and using its results in food testing

Proficiency testing (PT) is an objective tool to assess the laboratory’s performance. Participation in PT helps laboratories self-monitoring and self-evaluating the reliability of results. Nowadays, together with the development of laboratories, the demand of participating PT schemes is increasing, and there are variety of PT providers and PT schemes correspondingly. Hence, without of appropriate criteria for selection of PT schemes and the purposes of participating PT, time, money and effort could be excessively consumed, especially for laboratories that perform numerous different tests. In this study, principles for choosing appropriate PT schemes and using the PT results effectively for laboratories, particularly in food testing laboratories were provided.

The Importance of Reagent Lot Registration in External Quality Assurance/Proficiency Testing Schemes

BACKGROUND Providers of external quality assurance (EQA)/proficiency testing schemes have traditionally focused on evaluation of measurement procedures and participant performance and little attention has been given to reagent lot variation. The aim of the present study was to show the importance of reagent lot registration and evaluation in EQA schemes. METHODS Results from the Noklus (Norwegian Quality Improvement of Primary Care Laboratories) urine albumin/creatinine ratio (ACR) and prothrombin time international normalized ratio (INR) point-of-care EQA schemes from 2009–2015 were used as examples in this study. RESULTS The between-participant CV for Afinion ACR increased from 6%–7% to 11% in 3 consecutive surveys. This increase was caused by differences between albumin reagent lots that were also observed when fresh urine samples were used. For the INR scheme, the CoaguChek INR results increased with the production date of the reagent lots, with reagent lot medians increasing from 2.0 to 2.5 INR and from 2.7 to 3.3 INR (from the oldest to the newest reagent lot) for 2 control levels, respectively. These differences in lot medians were not observed when native patient samples were used. CONCLUSIONS Presenting results from different reagent lots in EQA feedback reports can give helpful information to the participants that may explain their deviant EQA results. Information regarding whether the reagent lot differences found in the schemes can affect patient samples is important and should be communicated to the participants as well as to the manufacturers. EQA providers should consider registering and evaluating results from reagent lots.