[Problems in the diagnosis of AIDS].

Diagnosis of human immunodeficiency virus (HIV) infection depends mainly on the detection of HIV-specific antibodies in the serum. If a seropositive patient has symptoms and signs of AIDS indicator diseases he (or she) will be diagnosed as having AIDS. If a patient is seronegative to HIV, some other diseases should be evaluated to explain the symptom related to the immunodeficiency. However, diagnosis of AIDS may be possible when a patient has AIDS indicator diseases and decreased CD4 positive cell count (< 400/microliters). We should also pay attention to the HIV-2 infection and idiopathic CD4 lymphocytopenia (ICL) which has been reported to be related to clinical immunodeficiency. We had a few cases with indeterminate antibody positivity. If a patient's serum is repeatedly HIV-positive in a screening assay but repeatedly indeterminate in a confirmation assay, some other confirmation tests such as RIPA, PCR, p24 antigen assay, or virus isolation should be employed to demonstrate the presence of HIV-infection.