In vitro interference by acetaminophen, aspirin, and metamizole in serum measurements of glucose, urea, and creatinine

• We investigate the in vitro effects of three analgesic–antipyretic drugs.
• Exogenous interferents affect routine laboratory methods.
• Non-specific Jaffe reactions with drugs may cause positive or negative interference.
• Positive interference induced by acetaminophen, aspirin, and metamizole on urea and creatinine.
• In vitro interference alters the accuracy of serum measurements of creatinine.

ObjectiveHere we aimed to investigate the in vitro effects of three analgesic–antipyretic drugs frequently used in clinical practice in Mexico — acetaminophen (AAP), aspirin (ASA) and metamizole (MMZ) — on serum measurements of glucose, urea, and creatinine.Design and methodsEach analyte was measured in a base-serum pool spiked with the drugs at subtherapeutic, therapeutic, and toxic doses. Serum glucose and urea were measured using the hexokinase/G-6PDH and urease/GLDH kinetic assays, respectively. Serum creatinine (SCr) was measured with a Jaffe procedure based on the alkaline–picrate reaction and with an enzymatic dry-chemistry system. Measurements were carried out in IL-Monarch and Vitros DT60-II analyzers, respectively. Data were analyzed by the difference-paired interference test and by ANOVA.ResultsBy the kinetic Jaffe/Monarch procedure, we found positive interference by the drugs on the SCr measurements and by only ASA for urea measurement. For creatinine measurements, the total errors (TEs) were 22–51%, 18–105%, and 15–26% for AAP, ASA, and MMZ respectively, while for urea measurement the TE was 16–21% for ASA. A negative interference by MMZ on SCr (TE = − 47%), but no-interference for AAP or ASA, were found via the enzymatic/DT60-II system.ConclusionsIn vitro positive interference induced by AAP, ASA, and MMZ (via the alkaline–picrate reaction), or negative interference by MMZ (via a dry-chemistry system), on the SCr measurements highlights the importance of investigating all possible sources of variation that may alter the accuracy of the laboratory tests, in order to provide useful results for making medical decisions for optimal patient care.

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