1Amina
M. Medhat, 2Manal H. Abbas, 3Magda Z. Kenawy, 3Maha
M. Hendy and 2Mohamed Khaled M. Metwally
1Biochemistry Department, Faculty of Science, Ain
Shams University, 2Rheumatology Unit and 3Internal
Medicine Department, Ain Shams University Hospitals
Hidden 19S IgM rheumatoid factor (RF), is a 19S IgM RF that can be detected in the IgM containing fraction serum but not in the unfractionated serum. Hidden RF was investigated in 30 patients with seronegative juvenile rheumatoid arthritis (JRA) (mean age 8.7 ± 3.5 years old), 18 children with systemic lupus erythematosus (SLE) (mean age 9 ± 4.25 years old), 40 adult patients with seronegative rheumatoid arthritis (RA) (mean age 42.9 ± 13.5) and 88 adult patients with other connective tissue diseases (CTD) (mean age 30.2 ±15.2 years old). Sixty normal subjects (20 children with mean age 6 ± 6.4 years old and 40 adults with mean age 30 ± 10.2 years old) were also included. All patients were seronegative for RF by the classic methods. Disease activity was assessed by measuring the levels of erythrocyte sedimentation rate and C-reactive protein. In the children, the hidden RF was present in 66.6% of JRA patients and 16.6% of SLE, while in adults it was detected in 27.5% of RA, 11.3% of those with other CTD. In contrast none of the healthy controls was positive. Correlation between hidden RF titer and disease activity was significant (p<0.001) only in patients with JRA and RA. We concluded that the determination of hidden RF may be a useful tool and a mean for following disease activity in seronegative JRA and RA.