COMPARISON OF HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH FLUORESCENCE POLARIZATION IMMUNOASSAY FOR THE ANALYSIS OF VANCOMYCIN IN PATIENTS WITH CHRONIC-RENAL-FAILURE

Eighty-two plasma samples from patients with chronic renal failure und ergoing vancomycin treatment and hemodialysis (HD) were analyzed with fluorescence polarization immunoassay (FPIA) and high-performance liqu id chromatography (HPLC). Vancomycin was infused once and the samples were collected during three subsequent HD sessions at 2 h, 3 days and 5 days post-infusion. The HPLC method, modified from an earlier assay, was simple. There was a wide variation in the estimated concentration between the two assay methods. The results obtained by HPLC were 69% lower than those obtained by FPIA. This difference in vancomycin conce ntration was independent of the sampling time after vancomycin infusio n. HPLC analysis commenced approximately 1.5 year after that of FPIA. To study the effect of in vitro degradation, the vancomycin concentrat ion in ten of the samples was redetermined with FPIA during HPLC analy sis. The concentrations of those samples decreased to 78-98% (average 92%) of the original concentration. Because FPIA appears to lack speci ficity, there is a need of other methods such as HPLC for vancomycin m easurements, particularly in samples from patients with end-stage rena l failure.