A model for calculating measurement uncertainty in medical laboratories

Introduction: All medical laboratories that require recognition for competency assessment have to estimate the uncertainty of measurement of assay test results "where relevant and possible" (ISO 15189:2007 Medical laboratories - Particular requirements quality and competence). The repeated quantitative examination of an analyte with the same method will offer more or less different results. This is happening because the outcome of an assay depends not only upon the analyte itself but also upon few error factors that could yield doubts about the obtained result. The mathematical, quantitative expression of this doubt is known as uncertainty of measurement (UM). Methods: It is the responsibility of each medical laboratory to identify all error sources that can be quantified and converted in standard deviations that could be used to estimate the type A or B of uncertainty. In the case of Romanian medical laboratories, the European Accreditation (EA) accepted as reference documents for UM estimation the Guide to the Expression of Uncertainty in Measurement (GUM) and Romanian Standard SR ENV 13005. Discussion and conclusion: In this paper, authors present and discuss the modalities of UM estimation in two different situations: when the used reference materials (calibrators) are or are not traceable to certified reference materials (CRM). Complete and informative UM reporting can only lead to better decisions in healthcare.