Poor performance of the utility of the serological diagnosis of pulmonary tuberculosis in Nigeria

Introduction Pulmonary tuberculosis (PTB) is the most common form of tuberculosis. In Nigeria, PTB is diagnosed by sputum smear microscopy. The problems associated with the diagnosis of PTB using sputum smear for acid-fast bacilli and culture has provided an urgent need to assess the utility of serological tools as an adjunctive diagnostic tool in presumptive PTB cases. This study is aimed at testing the diagnostic utility of a specific immunoglobulin G (IgG) serological assay in the diagnosis of PTB. Patients and methods A utility study was conducted on 184 participants of which 92 were smear-positive PTB cases and 92 were healthy controls at the TB and Leprosy Centre and Ahmadu Bello University Teaching Hospital, Zaria. Data were collected on age and sex, and both PTB patients and controls were screened for anti-TB IgG antibodies by enzyme-linked immunosorbent assay technique. Results The mean age of the participants was 35, and the male-female ratio was 1 : 4. Twenty-one (5.7%) of the PTB patients tested positive for IgG antibodies, and 11 (1.3%) of the controls were positive. The sensitivity of the IgG antibody assay was 18.4%, with the specificity being 92.3%, while the predictive values were 70.8 and 53.1% for positive and negative results, respectively. Conclusion The IgG antibody assay is poorly sensitive; serology may not have a role in the diagnosis of PTB in resource-limited settings, but the much higher specificity suggests that it may be useful as an adjunctive diagnostic tool, or for monitoring of patients on treatment for PTB.