Measurements for 8 Common Analytes in Native Sera Identify Inadequate Standardization among 6 Routine Laboratory Assays

Abstract

BACKGROUND External quality assessment (EQA) with commutable samples is essential for assessing the quality of assays performed by laboratories, particularly when the emphasis is on their standardization status and interchangeability of results. METHODS We used a panel of 20 fresh-frozen single-donation serum samples to assess assays for the measurement of creatinine, glucose, phosphate, uric acid, total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides. The commercial random access platforms included: Abbott Architect, Beckman Coulter AU, Ortho Vitros, Roche Cobas, Siemens Advia, and Thermo Scientific Konelab. The assessment was done at the peer group level and by comparison against the all-method trimmed mean or reference method values, where available. The considered quality indicators were intraassay imprecision, combined imprecision (including sample–matrix interference), bias, and total error. Fail/pass decisions were based on limits reflecting state-of-the-art performance, but also limits related to biological variation. RESULTS Most assays showed excellent peer performance attributes, except for HDL- and LDL cholesterol. Cases in which individual assays had biases exceeding the used limits were the Siemens Advia creatinine (−4.2%), Ortho Vitros phosphate (8.9%), Beckman Coulter AU triglycerides (5.4%), and Thermo Scientific Konelab uric acid (6.4%), which lead to considerable interassay discrepancies. Additionally, large laboratory effects were observed that caused interlaboratory differences of >30%. CONCLUSIONS The design of the EQA study was well suited for monitoring different quality attributes of assays performed in daily laboratory practice. There is a need for improvement, even for simple clinical chemistry analytes. In particular, the interchangeability of results remains jeopardized both by assay standardization issues and individual laboratory effects.

Analytical performance of 17 general chemistry analytes across countries and across manufacturers in the INPUtS project of EQA organizers in Italy, the Netherlands, Portugal, United Kingdom and Spain

“…For many analytes, our findings were comparable, e.g. glucose and cholesterol met, quality criteria whereas HDL cholesterol (Abbott) did not [8], neither did calcium and total protein meet the criteria [6]. We found that alkaline phosphatase (AP), alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), and lactate dehydrogenase (LD) were not traceable to the respective IFCC RMPs.…”

“…It is possible that other contrasting findings, e.g. uric acid and Mg (Abbott) had a similar cause [6].…”

“…There are only a few EQA schemes using commutable samples, most of them related to the group of Thienpont et al [6][7][8][9]. It is worth considering the differences between our two approaches in terms of the findings of our schemes and the use of slightly different samples.…”

“…Standardization and harmonization efforts minimize differences between laboratories and are the core issues of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and the American Association of Clinical Chemistry (AACC) [4,5]. External quality assessment (EQA)/proficiency test (PT) organizers play an important role in monitoring the performance of individual laboratories, but also in supplying information on the progress of standardization/harmonization efforts [6][7][8][9]. In a recent review, EQA/PT schemes are categorized on basis of three characteristics: (a) commutability of the samples, (b) value assignment of targets (with a RMP or not), and (c) inclusion of replicate samples (yes or no) [10].…”

A new integrated tool for assessing and monitoring test comparability and stability

“…The focus of the master comparisons, which are conducted across assays and laboratories, is on how well the intrinsic analytical quality of assays released by the respective manufacturers is reproduced by the end users under "field" conditions all over the world. Results about master comparison with a panel of 20 frozen single donation samples for calcium, magnesium, albumin, total protein [16,17], sodium [18], creatinine, glucose, phosphate, uric acid, total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides [19], have been previously described. In a recent survey AST, ALT, LDH, GGT and ALP, sodium, potassium and chloride have been added.…”