Difficulty in Achieving Comparability of

Clinical chemistry is a field in which the reliability of measurement results has a major impact on decisions that directly affect human beings. The conditions un-der which the measurements are performed and the way their results are applied bring about very stringent requirements in regard to the methods used. Measure-ments are expected to give reliable results after a single determination performed directly on complex matri-ces like serum or urine, and data should preferably be available within minutes to a few hours. The results need to be reliable (i.e., accurate) enough to enable comparisons with reference intervals and cutpoint val-ues, and the measurement target should be a clinically significant parameter. These requirements can cur-rently bemet for hundreds of analytes. The next level of requirement is that measurement results be compara-ble between laboratories and methods, over time, with common reference ranges for different methods. This has been achieved only for a much smaller number of analytes