Failure of the Treponema pallidum immobilization test to provide additional diagnostic information about contemporary problem sera.

Two hundred forty-five sera submitted to the Center for Disease Control, Atlanta, Ga., (CDC) were analyzed serologically in an attempt to demonstrate the diagnostic value of the Treponema pallidum immobilization (TPI) test when performed in addition to the fluorescent treponemal antibody-absorption (FTA-Abs) test. Diagnoses for the patients whose sera were tested were based on information supplied by the referring physicians. Fifty-four per cent of the diagnostic problems were resolved merely by the finding of a negative result with the FTA-Abs test. There was agreement between the serologic results of the referring laboratory and those of the CDC for 76% of sera tested by the Venereal Disease Research Laboratory test and for 71% of sera tested by the FTA-Abs test. For patients with treponemal disease, the sensitivity of the TPI test was 56% and that of the FTA-Abs test was 78%. When the FTA-Abs test was reactive, a negative TPI test was not significantly associated with systemic lupus erythematosus (P > 0.6) or other collagen vascular disease (P > 0.6), nor was a positive TPI test associated with treponemal disease (P > 0.09). It is concluded that once the result of the FTA-Abs test is known, the TPI test does not provide additional diagnostic information.