Rapid identification of the invading microorganism.

There has been great progress in recent years in the development of sensitive techniques for the rapid identification of microorganisms in material obtained from patients with a wide variety of infections. While some of these methods employ chemical and microscopic analysis, most investigative interest has centered on the detection of specific antigens by exquisitely sensitive immunologic tests. Properly used, these techniques can yield specific diagnoses within a matter of a few hours, thus facilitating management of both patient and others who are at risk for contracting the infection. Because these techniques detect antigens rather than viable organisms, specific diagnosis is also possible when antibiotic therapy administered prior to testing has rendered cultures sterile. In some instances assay of the concentration of antigen present in biologic fluids can be used in prognosis.