Performance of a fluorescence polarization immunoassay for teicoplanin in serum

Teicoplanin is a new glycopeptide antibiotic that is structurally related to vancomycin, but has six major components and is > 90% protein bound. We have developed a competitive homogeneous fluorescence polarization immunoassay (FPIA) for the quantitative determination of teicoplanin in serum. The teicoplanin FPIA uses six serum-based calibrators over the range 0-100 micrograms/ml, with the lowest teicoplanin concentration at 5 micrograms/ml and a lower limit of detection of < 1.5 micrograms/ml. Samples with concentrations > 100 micrograms/ml can be analyzed after 1:5 dilution with serum. Intra- and interassay precision are < 2% and < 4.5%, respectively, for controls at 7.5, 35, and 75 micrograms/ml on an automated FPIA analyzer. Recovery results for 30 samples prepared from the teicoplanin analytical reference standard over the range 3.4-358 micrograms/ml were linearly correlated with target concentrations; the linear regression equation and correlation coefficient are FPIA = 0.976 x target + 0.120, r = 0.999. Abnormal levels of bilirubin, hemoglobin, albumin, triglycerides, or cholesterol did not significantly affect recovery. Cross-reactivity with vancomycin was < 0.2%, and there was no significant interference from above therapeutic levels of likely concomitant medications. Results on patient samples from the teicoplanin FPIA were highly correlated with both a high-performance liquid chromatography (HPLC) method (FPIA = 1.032 x HPLC + 2.79, r = 0.979, n = 203) and the reference teicoplanin microbiologic assay method (orthogonal regression; FPIA = 1.111 x bioassay + 2.107, r = 0.969, n = 1014). A version of the teicoplanin FPIA for use with a modular clinical research FPIA analyzer showed comparable performance in all respects to the automated assay.