Possibilities for quality assurance of reference intervals.

Most clinical laboratories participate in surveys of external quality assurance (EQA). The results are not, however, very commonly or effectively applied to controlling the accuracy, i.e., differences in the analytical level. Therefore, it is important that each laboratory has its own, valid reference values. Nevertheless, many laboratories do not follow the internationally accepted recommendations for determining reference intervals or use reference values from other laboratories or from literature. Techniques of the external quality assurance can be extended to the checking of the validity of reference limits.