Quantitation of haptens by homogeneous immunoprecipitation. 1. Automated analysis of gentamicin in serum

A new homogeneous immunoprecipitation inhibition assay has been developed to quantitate concentrations of hapten in human serum or plasma without the use of radioactive isotopes, enzymes, fluorescent markers, or laser nephelometers. This immunoprecipitation is based on spectrophotometric measurement of the inhibition by free hapten of the precipitating reaction between antihapten antibody and polyhaptenic antigen. The immunoprecipitation analysis of the antibiotic gentamicin in human serum is reported here. A serum test sample is mixed with gentamicin-human serum albumin polyhaptenic conjugate and rabbit antiserum to gentamicin on a centrifugal analyzer, and the subsequent reaction monitored for 3 min. No sample dilution or pretreatment is required. The within-run and between-run coefficients of variation are well below 10%. The results on patients' test samples correlate well with those obtained by commercially available radioimmunoassay and enzyme immunoassay kits.