ObjectiveTo assess the frequency of CD4+ T-lymphocyte depletion in selected populations in West Africa and to determine whether an association exists between AIDS-like illnesses and CD4+ T-lymphocytopenia in HIV-negative individuals.DesignRetrospective review of databases and prospective case-control study.SettingProjet RETRO-CI, an AIDS research project in Abidjan, Côte d'lvoire, a University Hospital and tuberculosis treatment and maternal and child health centres in Abidjan.MethodsWe conducted a retrospective review of CD4+ T-lymphocyte counts performed between 1991 and 1992 on hospitalized medical patients, outpatients with tuberculosis, and women participating in a study of HIV-1 and HIV-2 mother-to-child transmission. A prospective case-control study was conducted in 1992 to examine the relationship between HIV-negative CD4+ T-lymphocyte depletion and wasting syndrome (wasting and chronic diarrhoea and/or chronic fever).ResultsIn the retrospective data review, CD4+ T-lymphocyte counts < 300 × 106/l were found in 9.6% of 115 HIV-negative hospitalized patients, in 4.2% of 312 ambulatory tuberculosis patients, and in 0.4% of 263 healthy women after delivery. In the case-control study, no association was found between CD4+ T-lymphocyte depletion in HIV-negative individuals and the presence of wasting syndrome. Increased mortality in HIV-negative individuals was associated with wasting but not with reduced CD4+ T-lymphocyte counts. In contrast, a trend existed for increased mortality with increasingly severe CD4+ T-lymphocyte depletion in HIV-positive patients. Tuberculosis was the most frequently proven or suspected diagnosis in HIV-negative individuals with wasting and CD4+ T-lymphocytopenia.ConclusionsIn the absence of HIV infection, CD4+ T-lymphocytopenia is uncommon ( < 1%) in West African asymptomatic individuals but is more frequent in those with tuberculosis (4%) and hospitalized patients (10%). CD4+ T-lymphocytopenia in HIV-negative individuals was not associated with wasting syndrome or increased mortality. There was no evidence for frequent, clinically relevant immune deficiency other than that associated with HIV infection.