Interferon-γ Release Assay Effective in Patients with COPD Complicated with Pulmonary Tuberculosis

By LabMedica International staff writers
Posted on 27 Jan 2025

Image: The diagnostic sensitivity of the interferon-γ release assay was higher in patients with COPD complicated with active pulmonary tuberculosis (Photo courtesy of Adobe Stock)

Chronic obstructive pulmonary disease (COPD) is a common respiratory condition and a major chronic lung disease that significantly impacts public health and work capacity. Long-term respiratory infections in COPD patients can weaken local respiratory immunity. Due to their immunosuppressive status and frequent corticosteroid use, COPD patients are more vulnerable to developing pulmonary tuberculosis. Conventional diagnostic methods for tuberculosis have shown decreased sensitivity in COPD patients, highlighting the need for more effective diagnostic tests that are easily accessible, well-accepted, simple to administer, and, most importantly, more sensitive in detecting tuberculosis. In a new study, an interferon-γ release assay has demonstrated higher diagnostic sensitivity in COPD patients with pulmonary tuberculosis than other diagnostic methods.

The nested case-control study, conducted between January 2019 and June 2021 at the Fifth Hospital of Shijiazhuang (Hebei, China), involved 123 COPD patients. Thirty-one patients with active pulmonary tuberculosis and COPD formed the observation group (Group A), 31 with nonactive pulmonary tuberculosis and COPD made up the COPD control group (Group B), and 31 patients with active pulmonary tuberculosis without COPD were the non-COPD control group (Group C). Diagnostic tests including interferon-γ release assay, purified protein derivative of tuberculin (PPD) test, anti-tuberculosis antibody test, sputum smear microscopy, and PCR for Mycobacterium tuberculosis were administered to each group. The researchers compared the positive detection rates from all five diagnostic methods.

The results, published in BMC Infectious Diseases, showed that the interferon-γ release assay had higher diagnostic sensitivity for active pulmonary tuberculosis in COPD patients than sputum smear microscopy, PCR, or serum anti-tuberculosis antibody tests. COPD complications did not impact the T-SPOT test results, and higher T-SPOT values indicated a greater likelihood of active tuberculosis. Based on these findings, the researchers recommend that T-SPOT-positive patients, who are clinically considered to have inactive tuberculosis, undergo regular follow-ups to monitor any changes in their condition.