Analytical interferences of drugs in clinical chemistry

The effects of several drugs were tested on analytical methods used in the clinical laboratory to measure the concentration of certain chemical constituents and activity of enzymes in body fluids. Drugs were studied initially at reported toxic concentrations, but if they had an effect at this level effects of lower concentrations were also investigated. The drugs were first studied on the methods of the Technicon SMACTM analyzer. Subsequently, methods in use with the Du Pont ACA and Technicon AutoAnalyzerTM I or II were evaluated. The most commonly affected method was the phosphotungstate reduction procedure for measuring uric acid. However, methods for measuring total protein and albumin were also affected frequently, as were determinations of alkaline phosphatase and lactate dehydrogenase activity.