Clinical significance of rheumatoid factor positivity in patients with smear-positive pulmonary tuberculosis

Background: Pulmonary tuberculosis (PTB) is a persistent infectious disease with immune disorder. Autoantibody, including rheumatoid factor (RF), is described during chronic infection; however, the clinical significance of RF in patients with smear-positive PTB has not been established. Objectives were to test the prevalence of RF positivity and its relation with severity of disease in the smear-positive PTB patients. Methods: A cross-sectional study was undertaken among 100 smears positive PTB patients. Information on demographics and clinical history was obtained through a structured questionnaire. Serum RF concentrations were determined by standard immunoassays. Sputum smear grading was done as per the national TB guidelines. Results of descriptive statistics were calculated for all variables and associations were tested employing chi-square tests. Results: Thirty percent of patients had RF positivity. The median serum RF concentration was 37.50 IU/ml (IQR: 27.75-55.50). It was found that patients with high sputum smear grading (2+ to 3+) were positive more for RF compared to low sputum smear grading (41.2% vs. 24.2%), but this association was not statistically significant (p=0.080). Conclusions: Positivity of RF was prevalent in smear-positive PTB patients and tended to be associated with higher bacillary load. Our data indicate that RF elevation may be associated with immune activation during active TB.