Diagnostic value of recombinant tuberculosis allergen and T-SPOT for the diagnosis of tuberculosis in patients with HIV infection

The aim of the study . To determine the diagnostic significance of recombinant tuberculosis allergen and T-SPOT for the diagnosis of tuberculosis in patients with HIV infection. Materials and methods . In 25 patients (72.0% (18/25) male and 28.0% (7/25) female), who had verified tuberculosis in combination with HIV infection, an immunological study was performed using the recombinant tuberculosis allergen and the TSPOT test. The statistical modeling method was simple logistic regression, calculating the likelihood ratio for intervals of the number of CD4 lymphocytes. Results and discussion . From the CD4 lymphocyte level of 200 cells/ml, the probability curve of a positive test result with the recombinant tuberculosis allergen increases sharply and, starting from the CD4 lymphocyte level of 600 cells/ml (the minimum threshold of a healthy person), takes on a probability close to 1.0 (100%). For the T-SPOT immunological test, the probability curve of a positive test result is more than 50% at a CD4 lymphocyte level of less than 200 cells/mll, approximately 100 cells/mll, and at a CD4 lymphocyte level slightly above 200 cells/ml, the probability curve approaches 1.0 (100%). Conclusion . In diagnostically difficult cases in a patient with HIV infection, it is preferable to use an immunological test with T-SPOT to detect tuberculosis when the number of CD4 lymphocytes decreases to less than 200 cells/ml.