Abstract: In high volume laboratory analysis of patient medical specimens, control materials are inserted at periodical intervals (e.g. once per eight hours) and analyzed. If the results of the analysis deviate from the mean according to statistical rules, the run of analyses prior to the insertion of control materials has in the past been rejected, often causing a substantial loss of results because the control materials were not inserted sufficiently frequently. According to the invention the patient mean of a test is determined, and when the mean deviates from the predetermined mean by more than a selected amount, this determination is used, not to reject the run, but rather to trigger insertion and analysis of control materials. If the analysis of control materials shows that the run is in control, the analyses made prior thereto are reported and the run is resumed. If the control material analysis shows that the run is out of control, then the prior analyses are rejected.