Evaluation of the anthraxin skin test for diagnosis of acute and past human anthrax.

A skin test for the diagnosis of human anthrax was evaluated as an alternative to bacteriological confirmation of human anthrax, which is possible in 10-40% of cases within the first three weeks of the disease only. The anthraxin skin test, which detects anthrax cell-mediated immunity, was positive in 81.8% of cases in the first three days of the disease, and in 97-99% of cases in the next two to three weeks. The positivity rate was 98.5% in the first 1.5 months of convalescence, 92.8% in the next 3 years, 82.8% in the following 4 to 15 years, and 72.7% 16 to 31 years after recovery. Thus, the anthraxin skin test appears to be a valuable method for early diagnosis of acute anthrax as well as the only method available for retrospective diagnosis of human anthrax.