Diagnostic value of interferon-γ release assay in patients with COPD complicated with pulmonary tuberculosis

The common diagnostic methods for tuberculosis have been showing reduced sensitivity among chronic obstructive pulmonary disease patients. This study was conducted to evaluate and analyse the diagnostic value of an interferon-γ release assay in COPD patients complicated with pulmonary tuberculosis.

A nested case-control study was conducted on 123 COPD patients hospitalized at the Fifth Hospital of Shijiazhuang, Hebei Province, from January 2019 to June 2021. Thirty-one patients with active pulmonary tuberculosis complicated with COPD composed the observation group (Group A), 31 patients with nonactive pulmonary tuberculosis complicated with COPD composed the COPD control group (Group B), and 31 patients with active pulmonary tuberculosis not complicated with COPD composed the non-COPD control group (Group C). An interferon-γ release assay, a purified protein derivative of tuberculin (PPD) test, an anti-tuberculosis antibody test, a test of Mycobacterium tuberculosis by sputum smear microscopy and a test of Mycobacterium tuberculosis by PCR method were used to test patients in each group. The positive detection rates generated from the five test methods were compared and analysed.

In COPD patients complicated with active pulmonary tuberculosis, the differences in the percentage of patients with positive interferon-γ release between the PPD test, anti-tuberculosis antibody test, Mycobacterium tuberculosis by sputum smear microscopy and PCR test results were statistically significant.

In patients with COPD complicated with active pulmonary tuberculosis, the percentage of patients who were positive according to the interferon-γ release assay was higher than that according to the sputum smear microscopy, PCR detection of Mycobacterium tuberculosis in sputum specimen, and detection of anti-tuberculosis antibodies. COPD-related complications did not affect the T-SPOT; the greater the T-SPOT value was, the greater the likelihood of active TB. For patients who are T-SPOT positive but clinically considered to have inactive tuberculosis, regular follow-ups should be performed to observe changes in the patient's condition.