Comparison of Serum Vancomycin Concentrations using a New Automated Analyzer based on High-Performance Liquid Chromatography and Chemiluminescent Immunoassay

Many immunoassay methods have been developed for quantifying vancomycin levels in biological fluids. Recently, the LM1010, a high-performance liquid chromatography-based medical diagnostic device was approved. This study compared the results obtained with LM1010 with those obtained using ARCHITECT plus chemiluminescent immunoassay (CLIA) to measure vancomycin levels in patient serum samples. The retention times measured with LM1010 for vancomycin and its major and minor crystalline degradation products (CDP-1) were 2.50, 2.38, and 1.91 min, respectively, and the separation was satisfactory. When five CLIA calibrator samples (5.0 – 100 μg/mL) were analyzed using LM1010, the concentrations were lower than expected, with an average of −12.96％ (range: −7.07％ to −17.53％). In addition, in a Japanese external quality control survey examination, LM1010 demonstrated high accuracy (0.33％ to −6.68％). A strong correlation was observed between the results obtained using LM1010 (calculated by peak height) and CLIA (r = 0.9682). The slope of the Deming regression comparing LM1010 to CLIA was 0.831, and a Bland–Altman plot for LM1010 relative to CLIA showed a mean negative bias (±1.96 standard deviation) of −2.356 (−6.108 – 1.396) μg/mL. Thus, the results obtained with CLIA were higher than those obtained with LM1010. If the calibrators for CLIA are adjusted by considering cross-reactivities with CDP-1 or other metabolites, the vancomycin concentrations in patient samples determined using CLIA may be higher than those determined using LM1010. Overall, vancomycin concentrations should be analyzed using an assay with higher accuracy, such as LM1010.