Drug interferences with clinical laboratory tests

The interpretation of clinical laboratory tests is dependent on a host of physiological, environmental and pharmacological factors. At present, it is difficult to determine which of these broad groups is involved when one suspects interference with a clinical laboratory test. Detailed knowledge of the drugs that a patient is consuming is critical in understanding potential interferences. Drugs affect laboratory tests by 2 basic mechanisms: (a) physiological or pharmacological interference, and (b) chemical interference. The major interferences with routine clinical chemistry tests are described in the review which follows. The diversity of therapeutic agents that influence tests, points to the problem of monitoring drug interferences. Awareness of the problem and careful review of drug histories is at present the only realistic method of attempting to minimise the problem. Future use of computer data bases may allow potential drug interferences to be signalled automatically.