LAUSR

There is considerable variation in laboratory practices with regard to the review of internal quality control (IQC), and the literature is not exhaustive on the subject of own control limits, its interpretation, when to switch it over, and its benefits for routine practice and even for patient monitoring. The purpose of the present article is to stress the routine interpretation and challenges related to own results for IQC management. The first 20 (initial) measures, as well as monthly and cumulative IQC results of immunochemical tests, were analyzed for the selected tumor markers and hormones. While the average tended to get closer to the manufacturer value by increasing the number of measurements, the analytical coefficient of variation (CVA) tended to increase. Most parameters showed significant differences between initial and cumulative CVA, which were lower than the manufacturer’s specifications. While the quality specifications based on biological variation best fit the analytical and clinical purpose of our laboratory tests, we must be aware that the manufacturer’s control range, and even the method specification, should be used carefully, because it is usually wider than our goals.