Anti-cyclic citrullinated peptide (anti-CCP) antibodies have been considered very specific for rheumatoid arthritis (RA). Some studies have shown that these antibodies can be positive in infectious diseases like TB, HIV, etc.
Fifty patients of tuberculosis both pulmonary and extra-pulmonary were enrolled in the study from inpatient and outpatient departments from May 2012 to November 2013. Anti-CCP antibody test was done in all the patient by ELISA.
Thirty one were pulmonary and 17 were extra-pulmonary and two were disseminated extra-pulmonary TB. Of the 31 cases of pulmonary tuberculosis, 12 cases (38.7%) were positive for anti-CCP antibodies and 19 cases (61.3%) were negative for same. Of the 19 cases of extra-pulmonary tuberculosis, two cases (10.52%) were positive for anti-CCP antibodies and 17 cases (89.48%) were negative. Of the 31 patients of pulmonary TB, nine were sputum positive and 22 were negative. Of those with sputum positive five (55.56%) were positive for anti-CCP antibodies and those with sputum negative 7 cases (31.81%) were positive for anti-CCP antibodies.
Anti-CCP can be falsely positive in cases of tuberculosis. Positivity of anti-CCP antibodies for tuberculosis is more for pulmonary (more for sputum-positive than sputum-negative) than extra-pulmonary TB. Anti-CCP thus is not very specific for rheumatoid arthritis.