Clinical impact of rapid susceptibility testing.

The clinical impact of susceptibility testing in general, and rapid same-day susceptibility tests in particular, was assessed from two perspectives: does the performance of susceptibility testing in the laboratory influence the clinical use of antibiotics? Does laboratory susceptibility testing affect the outcome of patients with infectious diseases? The following conclusions were derived from this investigation. In vitro susceptibility testing does significantly influence antibiotic usage, but it is difficult to demonstrate a direct relationship between the results of the susceptibility tests and disease outcome. There is little objective evidence to support the contention that rapid susceptibility tests have a greater clinical impact than traditional overnight procedures. Additional studies directed at addressing this issue are clearly necessary, however; in the absence of such studies, routine performance of same-day susceptibility testing should be considered only if the cost of such testing is less than the cost of overnight procedures, or if cost is not a limiting consideration.