Evaluation of four assay methods for determination of tobramycin in human serum

Four assay procedures for tobramycin in serum--enzyme immunoassay (I), substrate-labeled fluorescent immunoassay (II), radioimmunoassay (III), and bioassay (IV)--were compared and evaluated by replicate and analytical recovery studies. I and II were about 50% more precise than III and IV. II was substantially more nearly accurate than the other methods and also gave the best reproducibility (correlation coefficient 0.992 between-day). The least expensive method was IV. Ease of handling favored I and II. Overall, we find II to be the most acceptable procedure for use in the clinical laboratory.