Objective: To evaluate immunoglobulin G (IgG) and immunoglobulin A (IgA) responses to tuberculous-glycolipid antigen (TBGL-IgG and -IgA) in pulmonary tuberculosis (TB) patients and healthy controls in Thailand.
Design: Anti-TBGL antibody titres and other TB related markers were measured in the serum samples of 24 adults with pulmonary TB (PTB), 28 healthy adults (HA), 23 children with TB (CTB) and 24 healthy children (HC).
Result: Both TBGL-IgG and -IgA titres were significantly higher only in adult PTB cases compared to controls (P < 0.001 for all). TBGL-IgG was highly sensitive (92%) in PTB patients, but frequent positive proportions of TBGL-IgG (46%) and -IgA (36%) in HAs were the cause of low specificities of TBGL-IgG (54%) and -IgA (64%); that of TBGL-IgG+IgA (75%) was the highest. Antibody titres were positively correlated in TBGL-IgG+IgA double-positive HAs (HA+, 7/28, P < 0.01), but not in HA- (P > 0.05). Serum IgG and IgA levels were not correlated with TBGL-IgG or -IgA levels (P > 0.05). KL-6 and leptin levels were normal and were not different between HA+ and HA-, indicating absence of active TB in HAs.
Conclusion: Enhanced TBGL-IgG+IgA responses in HAs could indicate latent TB infection. Careful follow-up studies in HAs could clarify the significance of elevated TBGL antibodies as early disease markers.