Full method validation in clinical chemistry

Abstract

Clinical chemistry is subject to the same principles and standards used in all branches of metrology in chemistry for validation of measurement methods. The use of measuring systems in clinical chemistry is, however, of exceptionally high volume, diverse and involves many laboratories and systems. Samples for measuring the same measurand from a certain patient are likely to encounter several measuring systems over time in the process of diagnosis and treatment of his/her diseases. Several challenges regarding method validation across several laboratories are therefore evident, but rarely addressed in current standards and accreditation practices. The purpose of this is paper to address some of these challenges, making a case that appropriate conventional method validation performed by the manufacturers fulfils only a part of the investigation needed to show that they are fit for purpose in different healthcare circumstances. Method validation across several laboratories using verified commercially available measuring systems can only be performed by the laboratories-users themselves in their own circumstances, and need to be emphasised more by the laboratories themselves and accreditation authorities alike.

Uncertainty From Sampling

“…Several publications deal with the uncertainty from sampling (Theodorsson & Magnusson, 2017;Ramsey & Ellison, 2017;Kallner, 2001), but only a few address this issue in a practical way to quantify the uncertainty arising from it. The easy access to samples does not necessarily mean that sampling replication is realistic, bearing in mind ethical issues.…”

“…Uncertainty in the pre-examination processes is attributed to preanalytical variation and, sometimes, biological variation (Theodorsson & Magnusson, 2017), referring to the variance in test results within a single individual over a specified period. It is understood how important this phase is and the extent to which several factors during this phase can result in nonconformities and failures.…”