Comparative Diagnostic Utility of Neopterin and IFN-γ/IL-2 in Extrapulmonary Tuberculosis

Resurgence of TB has emphasized the need for newer methods of diagnosis. Extrapulmonary tuberculosis (EPTB), being paucibacillary, is a diagnostic dilemma. The aim of the present study was to correlate IFN-γ/IL-2 with neopterin in diagnosis of EPTB. Extrapulmonary specimens from 69 clinically diagnosed cases were stained by Ziehl-Neelsen and cultured on Lowenstein-Jensen medium for Mycobacterium tuberculosis. ELISA was used to assess serum IFN-γ, IL-2 and neopterin levels. Median serum levels of IFN-γ/IL-2 and neopterin were 3.22 and 21.6 nmol/L in clinically diagnosed EPTB cases and 0.52 and 4.20 nmol/L in healthy controls respectively (p < 0.001). Both IFN-γ/IL-2 and neopterin were significantly higher in culture positive (14.64 and 49.8 nmol/L) than culture negative cases (3.01 and 17.5 nmol/L) respectively (p < 0.05). IFN-γ/IL-2 was significantly higher in AFB smear positive cases (8.63) than smear negative cases (3.04) (p = 0.003), whereas no significant difference in neopterin levels was seen (p = 0.307). A positive correlation between IFN-γ/IL-2 and neopterin was seen in EPTB cases (spearman's rho = 0.453, p < 0.001), whereas in healthy controls no such correlation existed (spearman's rho = 0.018, p = 0.884). An urgent need for research in the field of biomarkers exists to utilize them as point of care test in the diagnosis of EPTB.