Vancomycin assay performance in patients with acute renal failure

Objective: Fluorescence polarization immunoassays (FPIA) have been reported to overestimate vancomycin serum concentrations compared to high-performan ce liquid chromatography (HPLC) or enzyme multiplied immunoassay technique (EMIT) in patients with chronic renal disease. The assay manufacturer has m odified the FPIA to remedy this overestimation. The purpose of this study w as to compare the assay performance of two FPIAs to EMIT in acute renal fai lure patients receiving vancomycin and continuous venovenous hemofiltration . Design: Open-label trial. Setting: Intensive care unit in a university affiliated hospital. Patients and participants: 15 serum and ultrafiltrate samples were obtained from 14 critically ill patients (mean +/- SD; 57 +/- 12 years; 8 males/6 f emales). Measurements and results: Vancomycin concentrations were determined by a po lyclonal FPIA (pFPIA) performed on the TDx system, a monoclonal FPIA (mFPIA ) performed on the AxSYM system and EMIT. The coefficient of variation for all assays was < 5%. The mean difference +/- SD, between mFPIA vs EMIT and pFPIA vs EMIT assays in serum were: -0.08 +/- 1.55 and 1.24 +/- 2.11 mg/l, respectively. The limits of agreement between the mFPIA vs EMIT and pFPIA v s EMIT assays in serum were: -3.18 to 3.03 and -2.99 to 5.46 mg/l, respecti vely. Conclusions: Our data demonstrate that the manufacturer's changes to the pF PIA have reduced overestimation. The mFPIA appears to be an acceptable assa y for measuring vancomycin serum concentrations in acute renal failure pati ents and does not significantly overestimate these concentrations.