Effect of drugs containing lithium, salicylate and paracetamol as preanalytical variables on biochemical analysis parameters

Nowadays, laboratory tests play an important role in patient evaluations of physicians. When the errors affecting the medical laboratory test results are examined, it is seen that these errors are not caused by the analysis but rather by the preanalytical variables before analysis. When the sources of these errors are cheked, drug use is controllable preanalytical variable. There are limited data on interference effects of drugs used in medical practices on laboratory test results, despite the identification of accuracy of drug analysis results in therapeutic drug monitoring. The aim of this thesis study was to investigate the possible interferences of lithium carbonate, paracetamol and acetylsalicylic acid in subtherapeutic, therapeutic and toxic concentrations on serum measurements of some medical laboratory tests. Laboratory tests were conducted with the Cobas® 8000 series of modular analyzers (Roche Diagnostics, USA) to investigate the interfering effects of drugs. Cobas c-702 and Cobas c-502 modules were used to analyze glucose, urea, creatinine, total protein, albumin, aspartate aminotransferase, alanine aminotransferase, gamma glutamyl transferase, total cholesterol, triglyceride, high density lipoprotein-cholesterol, total bilirubin, uric acid, alkaline phosphatase, lactate dehydrogenase and creatine kinase. Inaddition, Cobas e-602 module was used to analyze thyroid stimulating hormone, free triiodothyronine (fT3), free tetraiodothyronine (fT4), vitamin B12 and folate. When the parameters analyzed by spectrophotometric and immunochemical methods are considered in interference studies, only significant in vitro interference was detected in the measurements of fT3 and fT4 in the toxic concentrations of acetylsalicylic acid. No significant interference exceeding TEa % values were found except for these two parameters. In addition in this study, the similar applications were conducted with sodium carbonate suitable for subtherapeutic, therapeutic and toxic lithium concentrations to assess the potential interfering effect of carbonate, and it was determined that the results of these applications showed similar profile with the results of lithium carbonate.