LAUSR

OBJECTIVE The aim of this study was to evaluate the influence of hemolysis, icterus, and lipemia (HIL) interferences on 8 therapeutic drug monitoring (TDM) assays. METHODS Amikacin, carbamazepine, digoxin, lidocaine, lithium, methotrexate, phenobarbital, and theophylline were spiked in specimen pools at the clinical decision cutoff values. The interferents were spiked in vitro in specimen pools. All analytes were tested on Beckman Coulter AU analyzers. RESULTS Hemolysis interference was detected in quantitative microsphere system (QMS) amikacin at 55.59 μg/mL at a concentration of 500 mg/dL hemoglobin. Icterus interference was detected in enzyme multiplied immunoassay technique amikacin at 43.62 μg/mL and in QMS amikacin at 55.59 μg/mL, at a concentration of 20 mg/dL bilirubin. CONCLUSION Although the reference range value is recommended for clinical significance bias assessment for HIL interferences on most chemistry assays, an important investigation of the HIL interferences on TDM assays is to establish interferent thresholds at the clinical critical cutoff values.