- Buffy coat for Mycobacterium intracellulare-avium (MAI) and cytomegalovirus (CMV) cultures; serum cryptococcal antigen; some measure of pulmonary function to exclude Pneumocystis carinii pneumonia including chest x-ray and either gallium scan, blood gases, or DLCO; stool culture and special stains for Salmonella, Isospora belli, cryptosporidium, CMV, and MAI in patients with diarrhea; computerized tomography (CT) scan or magnetic resonance imaging (MRI) of brain, or lumbar puncture for India ink, acid-fast bacilli smear, cryptococcal antigen, or fungal/mycobacterial culture.