FALSE-POSITIVE TREPONEMAL SEROLOGY IN PATIENTS WITH DIABETES-MELLITUS

In sera from 476 diabetic outpatients, positive reaction in the Fluore scent Treponemal Antibody-Absorption (FTA-Abs) test, a commonly used s erological test for syphilis, was found in 36 of the patients. None of 100 healthy control subjects were positive in the FTA-Abs test. Addit ional treponemal and nontreponemal tests confirmed the diagnosis of sy philis in only three of the diabetic patients. In 10 of the 36 patient s, the positive FTA-Abs reactivity appeared to be due to cross-reactiv ity between the treponemal antigen and Borrelia burgdorferi, which cau ses Lyme borreliosis. In the remaining 23 patients (5%), no other expl anation for a false-positive FTA-Abs reactivity was found besides diab etes. Diabetic patients with false-positive FTA-Abs reactivity had sim ilar degree of long-term metabolic control and prevalence of islet cel l antibodies (ICA) as well as late diabetic complications as FTA-Abs n egative diabetic patients, matched regarding to sex, age, type, and du ration of diabetes. In conclusion, false-positive FTA-Abs reactivity i s not rare in diabetic patients. The reason for this phenomenon is unk nown, but could be a sign of autoimmunity of its own. Hence, in diabet ic patients with FTA-Abs test indicating syphilis, the diagnosis must be verified with a combination of other tests.