Comparison of radioimmunoassay with a new immunofluorescent method (FIAX) for measuring tobramycin in serum.

A new immunofluorescent method (FIAX) was compared with a radioimmunoassay procedure for the determination of tobramycin serum concentrations. When assaying three tobramycin control sera repeatedly, within-run and run-to-run variations by the FIAX method were all within acceptable limits, and no statistically significant differences were found. Results of 155 sera from patients who had been treated with tobramycin showed a correlation coefficient of 0.93 between the two methods. The FIAX method represents another practical alternative for determining tobramycin serum levels.