LABORATORY DIAGNOSIS AND INTERPRETATION OF TESTS FOR SYPHILIS

The lack of a method for demonstrating the presence of Treponema palli dum by growth necessitates the use of alternative methods. Traditional ly, these methods are divided into direct detection methods (animal in oculation, dark-field microscopy, etc.) and serologic tests for the pr esence of patient antibody against T. pallidum. Serologic methods are further divided into two classes. One class, the nontreponemal tests, detects antibodies to lipoidal antigens present in either the host or T. pallidum; examples are the Venereal Disease Research Laboratory and rapid plasma reagin card tests. Reactivity in these tests generally i ndicates host tissue damage that may not be specific for syphilis. Bec ause these tests are easy and inexpensive to perform, they are commonl y used for screening, and with proper clinical signs they are suggesti ve of syphilis. The other class of test, the treponemal tests, uses sp ecific treponemal antigens. Confirmation of infection requires a react ive treponemal test. Examples of the treponemal tests are the microhem agglutination assay for antibodies to T. pallidum and the fluorescent treponemal antibody absorption test These tests ave more expensive and complicated to perform than the nontreponemal tests. On the horizon a re a number of direct antigen, enzyme-linked immunosorbent assay, and PCR techniques. Several of these techniques have shown promise in clin ical trials for the diagnosis of congenital syphilis and neurosyphilis that are presently difficult to diagnose.