Evaluation of an immunoassay for determination of plasma efavirenz concentrations in resource-limited settings
Journal of the International AIDS Society
Department of Medical Laboratory Sciences and Pathology, Jimma University, Jimma, Ethiopia; Department of Infectious Diseases, Odense University Hospital, Odense, Denmark; Department of Medicine, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa; Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
Introduction: Therapeutic drug monitoring (TDM) may improve antiretroviral efficacy through adjustment of individual drug administration. This could result in reduced toxicity, prevent drug resistance, and aid management of drug-drug interactions. However, most measurement methods are too costly to be implemented in resource-limited settings. This study evaluated a commercially available immunoassay for measurement of plasma efavirenz. Methods: The immunoassay-based method was applied to measure efavirenz using a readily available Humastar 80 chemistry analyzer. We compared plasma efavirenz concentrations measured by the immunoassay with liquid chromatography tandem mass spectrometry (LC-MS/MS) (reference method) in 315 plasma samples collected from HIV patients on treatment. Concentrations were categorized as suboptimal <1 μg/ml, normal 1-4 μg/ml or high >4 μg/ml. Agreement between results of the methods was assessed via Bland-Altman plot and k statistic values. Results: The median Interquartile range (IQR) efavirenz concentration was 2.8 (1.9; 4.5) mg/ml measured by the LC-MS/MS method and 2.5 (1.8; 3.9) μg/ml by the immunoassay and the results were well correlated (ρ =0.94). The limits of agreement assessed by Bland-Altman plots were - 2.54; 1.70 μg/ml. Although immunoassay underestimated high concentrations, it had good agreement for classification into low, normal or high concentrations (K = 0.74). Conclusions: The immunoassay is a feasible alternative to determine efavirenz in areas with limited resources. The assay provides a reasonable approximation of efavirenz concentration in the majority of samples with a tendency to underestimate high concentrations. Agreement between tests evaluated in this study was clinically satisfactory for identification of low, normal and high efavirenz concentrations. © 2014 Abdissa A et al;.
efavirenz; article; blood chemistry; blood sampling; chemical analyzer; controlled study; drug blood level; human; Human immunodeficiency virus infected patient; Human immunodeficiency virus infection; immunoassay; liquid chromatography; major clinical study; priority journal; tandem mass spectrometry; therapy; antiretroviral therapy; efavirenz; immunoassay; LC-MS/MS; method evaluation; TDM; Anti-HIV Agents; Benzoxazines; Chromatography, Liquid; HIV Infections; Humans; Immunoenzyme Techniques; Tandem Mass Spectrometry