EDUCATIONAL GUIDE Meeting ISO 15189:2012 Requirements for MU in the Clinical Laboratory QUALITY CONTROL

Meeting ISO 15189:2012 Requirements for Measurement Uncertainty in the Clinical Laboratory Measurement Uncertainty (MU) relates to the doubt that exists for the result of any measurement. For every measurement there is always a margin of doubt. In everyday speech, this might be expressed as ‘give or take’. Since there is always a margin of doubt for any measurement, the clinical lab needs to ascertain the width of the margin and the significance of the doubt. Two values are needed in order to quantify uncertainty; the width of the margin or interval, and the confidence level, which states how...

Data Collection Patient sample testing and comparison with a reference value is carried out over time. With this in mind, it is logical that the QC data used to carry out Uncertainty calculation is gathered in a similar fashion - over time. The Australian Association of Clinical Biochemists recommends that at least 6 months of QC data should be used to calculate Uncertainty. In addition to this, Westgard QC maintains that over 100 data points should be used to generate a representative Gaussian distribution of the test system. If 100 repeat measurements were taken in one day by an individual...

Other Factors Affecting Uncertainty It is important to consider bias when calculating uncertainty. Bias must be measured and if it is significant removed or minimised. If bias is not removed the uncertainty of the bias correction must be calculated and included in the overall uncertainty measurement. To calculate the uncertainty of bias we must first determine uRef and uRep: uRef – Uncertainty value of the analyte assigned to the reference material/EQA. This can be obtained from the reference material or EQA report. uRep – Uncertainty value of the analyte in the reference material/EQA when measured...