Lack of direct correlation between CD4 T-lymphocyte counts and induration sizes of the tuberculin skin test in human immunodeficiency virus type 1 seropositive patients

Setting: The study was conducted in Bobo-Dioulasso, Burkina Faso, where Mycobacterium tuberculosis infection and human immunodeficiency virus type 1 (HIV-1) infection are prevalent.Objective: To identify proportions of representative (test) populations who are reactive to the tuberculin skin test, and to study the relationship between CD4 T-lymphocyte counts and the induration size of the tuberculin skin test in these groups.Design: A group of 435 healthy students was tuberculin skin tested in order to evaluate the intensity of skin testing in a 'normal' population. The study group consisted of 195 subjects with or without tuberculosis, and with or without HIV-1 infection, who received a tuberculin skin test and a CD4 T lymphocyte count on the same day.Results: In total, 90% of the control (nontuberculous, HIV negative) subjects, 32% of the HIV-1 seropositive subjects, 76.5% of the tuberculous patients and 57% of the tuberculous HIV-1 seropositive patients were tuberculin positive. There was no direct correlation between the induration size of reactions to the tuberculin skin test and CD4 T-lymphocyte count in these study groups using linear regression analysis.Conclusion: In vivo skin testing using tuberculin yields clinically significant information on the degree of immunodeficiency which is different from that of CD4 T-lymphocyte counts. The tuberculin skin test should therefore be used as an independent marker of the weakened immunological status of HIV-1 seropositive subjects.