Significance of Tuberculin Testing in HIV Infection: An Indian Perspective

Area of Science:

• Immunology
• Infectious Diseases
• Public Health

Background:

• Tuberculin skin testing (TST) is crucial for diagnosing tuberculosis infection.
• However, TST can yield false-negative results in immunocompromised individuals, including those with HIV.

Purpose of the Study:

• To investigate the pattern of TST results in newly diagnosed HIV-positive patients.
• To assess the relationship between TST results, CD4+ lymphocyte counts, and tuberculosis development in this population.

Main Methods:

• Analysis of TST results in 523 newly diagnosed HIV-positive patients.
• Flow cytometry was used to determine CD4, CD8, and absolute lymphocyte counts in 63 patients.

Main Results:

• A significant association was found between higher TST induration (≥10 mm) and increased likelihood of developing tuberculosis.
• Lower CD4+ lymphocyte counts were observed in patients with nil TST results compared to those with ≥10 mm induration.
• HIV-infected patients with tuberculosis and positive TST had significantly lower average CD4 counts than those without tuberculosis.

Conclusions:

• In endemic regions like India, tuberculosis can emerge early in HIV infection with preserved immunity, showing positive TST results in nearly 45% of cases.
• Patients with TST results of 0-4 mm may have CD4+ counts below 200/cmm.
• Recommended high-risk groups for tuberculosis development include those with TST ≥10 mm and those with nil induration and CD4+ counts <200/cmm.