Drug effects on clinical laboratory tests.

Drugs and xenobiotics can affect clinical laboratory test results either by interfering with the analytical systems themselves, or by influencing endogenous constituents. National and international bodies have brought widespread recognition to this problem and have proposed protocols for its thorough scientific study. In this survey the authors discuss studies in their laboratories concerning the effects of drugs on thousands of patients undergoing a routine clinical screen. A database is described for storing both patient information and a detailed analysis of the published literature on drug effects. Analytical interferences in clinical tests must be examined in validating the procedure. However, highly specific analytical techniques are increasingly helping to reduce such interferences. Biological effects can be classified as physiological, pharmacological or toxicological. In some cases, biological effects can be used to advantage in monitoring treatment by potentially hazardous drugs, such as the cardiac glycosides. The requirement for a well-defined reference population for each drug and for access to all clinical and medical data for each patient is discussed. The need for greater awareness of the influence of drugs on clinical laboratory results is considered, together with the suggestion that the health professions should try to exploit such effects in monitoring possible toxicity problems, in defining genetic constitution and in designing medication programmes.