Dynamic IgG antibody response to immunodominant antigens of M. tuberculosis for active TB diagnosis in high endemic settings.

Balaji, P.; Prabhavathi, M.; Anbarasu, D.; Pugazhvanthen, P.; Raja, A.

Clinica Chimica Acta; 2016; 461:25-33.

Abstract: Background: Even though various techniques have been developed for rapid diagnosis of tuberculosis (TB), still there is an immense need for a simple, cost effective, highly sensitive and specific test. Hence, one of the possibilities is identification of Mycobacterium tuberculosis specific antibodies in infected serum by using specific antigens.

Methods: We tested 10 recombinant M. tuberculosis antigens to evaluate IgG levels among Healthy control subjects (HCS), Healthy household contacts (HHC) and pulmonary TB patients (PTB) by ELISA.

Results: The median IgG levels specific to all the antigens are higher in PTB than HHC and HCS. Amongst single antigens, 38-kDa antigen has showed maximum sensitivity of 50% than any other antigens at 95.5% specificity. Among the two antigen combination, 38-kDa + Rv1860 has showed maximum sensitivity of 66.6% with specificity of 92.2%. The same antigen combination (38-kDa and Rv1860) predominantly identifies smear negative and culture positive TB patients with 68% sensitivity and 92.2% specificity. Most of the antigens have exhibited higher antibody titre in cavitary TB than non cavitary. With regard to latent TB infection (LTBI) identification, Rv1860 has exhibited maximum sensitivity of 53.3% with 95% specificity.

Conclusions: IgG response to combination of recombinant mycobacterial antigens (38-kDa, Rv1860, Rv2204c and Rv0753c) presents good specificity with acceptable level of sensitivity for TB diagnosis.

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