A STUDY OF SERODIAGNOSIS OF SYPHILIS

I. A COMPARATIVE STUDY OF TPHA, FTA-ABS AND TWO METHODS OF STS

Abstract

Seroreaction tests for syphilis are indispensable before blood donation, at pre-marital health examination and during pregnancy, and the exclusion of biological false positive reaction (BFP) may be regarded as an urgent social problem, for the solution of which no efforts should be spared.
Since August, 1969, our blood center has adopted TPHA (Treponema Pallidum Hemagglutination Test) with a view to minimizing the appearance of BFP, but we have found that this method, too, is not free from defects. Accordingly in January, 1970 we began to employ FTA-abs (Fluorescent Treponemal Antibodies Absorption Test) together with TPHA. The sera of blood donors which positively reacted to CL-antigens were subjected to the above two methods in order to clarify the essential nature of BFP. The sera of some healthy persons, pregnant women and patients of the dermatological clinic were also used in this investigation.
It is inferred from results of the present investigation that a fairly large percentage of BFP is inevitable with two methods of CL reaction (slide and Ogata's tests).
TPHA and FTA-abs proved themselves excellent methods, and their results were generally in correspondence, but not in all cases. In FTA-abs non-specific reactions were sometimes not completely absorbed in the 1:5 serum dilution. Non-specific fluorescence was noted in 10% of healthy persons and in 13% of pregnant women. That is, with the 1:5 serum dilution very sensitive reactions were noted, but at the same time specificity was also fairly reduced.
Therefore, in FTA-abs serum dilution should be prepared in two gradations. Results obtained with the 1:20 dilution should be used for reading with especial reference to those with the 1:5 dilution.
Several interesting cases of the dermatological clinic were also reported in detail.