The incidence of tuberculosis is increased in HIV positive patients. Purified protein derivative (PPD, tuberculin) testing has not been performed routinely on patients infected with HIV in the UK and its usefulness in diagnosing tuberculosis in these patients is unclear.
198 HIV positive patients were Tine tested and a CD4+ lymphocyte count and chest radiograph were performed. Of the 179 male patients 164 were homosexual or bisexual, 11 were injecting drug users (IDUs), and four were both homosexual and IDUs. Of 19 women 14 were heterosexual and five were IDUs. Patients assessed their own skin reactions at 72 hours, recording the grade on a card which was returned by post. Patients with a grade 0 reaction were requested to have a second test one month later.
Details were available on 168 of the 198 patients. Grade 0 reactions occurred in 89 of the 168 patients, requiring a second Tine test, and 73 completed Tine 2 results were received. Of 57 patients with CD4+ lymphocyte counts below 200/mm3, low grade PPD reactivity was seen in 18 on Tine 1 and nine on Tine 2. No history of BCG immunisation of tuberculosis was found in 33 Tine positive patients. Two patients treated for tuberculosis in the previous six months were PPD positive with CD4+ counts of 60/mm3 and 4/mm3 respectively.
PPD reactivity may be maintained despite a CD4+ count of 100/mm3 or less when there is a history of tuberculosis or BCG immunisation.
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