The biological false positive reaction to serological tests for syphilis

Acute and chronic biological false positive reactions to serological tests for syphilis are discussed. Three cases are presented, one showing an acute and one a chronic reaction, and one in which it was not possible to determine if the reaction was acute or chronic. Once a biological false positive reaction is found, serum from the patient should be tested at intervals for at least six months to determine if the reaction is acute or chronic. If a chronic reaction is found the patient should then be investigated to find the underlying cause. Problem sera from 753 patients are reviewed. Biological false positive reactions were shown by 47 sera and 257 sera gave results indicating they came from patients infected with syphilis. The reactive sera were divided into four groups: sera from blood donors, antenatal patients, cases of recent vaccination, and a miscellaneous group. It was found that in the first three groups the number of sera from patients showing biological false positive reactions was equalled or exceeded by the number showing syphilitic reactions. Biological false positive reactions in sera from cases of lepromatous leprosy and in sera from the inhabitants of the Okapa region of New Guinea are also discussed. It is concluded that sera which give reactive results to reagin detection tests for syphilis and come from patients known to have conditions which cause acute or chronic biological false positive reactions should never be dismissed as such. Experience has shown that a number of these sera will give reactive Treponema pallidum immobilization test results, that is, they come from patients who have or have had syphilis.