VANCOMYCIN SERUM CONCENTRATIONS IN PATIENTS WITH RENAL DYSFUNCTION - A COMPARISON OF FLUORESCENCE POLARIZATION IMMUNOASSAY AND THE ENZYME-MULTIPLIED IMMUNOASSAY TECHNIQUE

A study was conducted to determine whether assay-specific quantitative differences exist in the determination of vancomycin serum concentrat ions obtained from patients with renal dysfunction. Vancomycin serum c oncentrations were obtained during the first week of therapy for each of three time intervals: 48-96 h, 96-144 h, and 144-192 h after admini stration of the first dose of vancomycin. Vancomycin serum concentrati ons were measured using the enzyme-multiplied immunoassay technique (E MIT) and fluorescence polarization immunoassay (FPIA). Twenty patients with an estimated creatinine clearance <40 ml/min who were receiving intravenous vancomycin were evaluated. Hemodialysis was required in 16 of 20 patients. Fifty samples were included in the data analysis. The mean (+/- SD) serum concentrations obtained with EMIT and FPIA were 1 0.9 mg/L (+/-5.3) and 12.6 mg/L (+/-5.7), respectively (p = 0.13), and were not statistically different. A linear relationship was observed between EMIT and FPIA(EMIT = 0.89 x FPIA - 0.24; r(2) = 0.93). No stat istically significant differences were observed in the calculated phar macokinetic parameters between methods. FPIA and EMIT are comparable m ethods in determining vancomycin serum concentrations within the first week of vancomycin therapy in patients with moderate to severe renal dysfunction.