Optimisation of the sensitivity of an immunoassay analysis for tobramycin in serum

Tobramycin is an aminoglycoside antimicrobial drug frequently used in anti-pseudomonal therapy in cystic fibrosis and non-cystic fibrosis bronchiectasis patients. Therapeutic drug monitoring is routinely performed to increase efficacy and reduce the chance of toxicity. The most frequently used method to quantify tobramycin in serum or plasma is with an immunoassay method. However, immunoassays lack sensitivity to evaluate the lower concentrations of tobramycin for pharmacokinetic studies of for instance inhaled tobramycin. The aim of this study was to optimise the Syva® Emit® 2000 Tobramycin Assay combined with the ARCHITECT c8000. This adapted method was validated for accuracy and precision, having within-run, between-run variation. The adapted tobramycin immunoassay method has a linear range of 0.03 to 0.6 mg/L, which is comparable to liquid chromatography-mass spectrometry methods. The immunoassay method was validated with representative samples and has been implemented in routine analysis.