IgG RF and anti-CCP2 antibody can be positive in undifferentiated arthritis due to streptococcal infection, hepatitis B virus, tuberculosis, trauma and hypothyroidism: a preliminary study.

Anti-CCP2 antibody and rheumatoid (RF) tests are used for the diagnosis of rheumatoid arthritis (RA). Out of these two, anti-CCP2 antibody is supposed to be more specific for RA. Aim of the study was to present 33 cases of undifferentiated arthritis (UA) in which features of RA were not present, but anti-CCP2 antibody was positive. Out of the 33 cases of UA, 19 had well-known disease like hyperthyroidism, hypothyroidism, tubercular arthritis, traumatic arthritis, pneumonia with arthritis, varicose vein with pain in legs, cervical spondylitis and SSA. The duration of disease was more than one year in 67.86% cases. Majority of the patients were females (63.64%). Knee joint involvement was seen in maximum number (i.e. 20 cases). All 33 cases were positive for anti-CCP2 Ab. Maximum number of cases (78.78%) had involvement of one or two joints. CRP positivity was seen in 23.07% cases. Morning stiffness was present in (36.36%) cases, while swelling of the joint was present in 33.33% cases. In 16 cases, only serum sample was available for further analysis. About 62.5% cases showed IgG RF positivity. Antitubercular IgM and IgG were detected in 18.75% cases; ASO was elevated in 12.5% cases, and HBs Ag was positive in 6.25% cases. None of the controls (30 cases) were positive for these infections, anti-CCP2 antibody or RF. Thus, our study concludes that chronic infections like streptococcus, hepatitis B, tuberculosis and autoimmune thyroid diseases can produce raised levels of anti-CCP2 antibody and IgG RF.