Diagnosis of PCP in HIV seropositive patients.

We read with interest the article by Sauleda and colleagues on the use of a simplified exercise test for the initial differential diagnosis of Pneumocystis carinii pneumonia (PCP) in HIV positive patients (February 1994;49:112-4) and would like to make the following points. Firstly, the risk factors for the acquisition of HIV infection were not given other than to state that 36 of the patients were intravenous drug users. It was not clear how these 36 patients divided between the two groups. Intravenous drug use is associated with impaired lung function independently of acquired infection and, in addition, intravenous drug users are more susceptible to pyogenic infections. Of the initial 60 subjects enrolled in the study 25%