Antiperinuclear and hidden rheumatoid factors in monitoring disease activity of juvenile rheumatoid arthritis

الملخص EN

Objective: The serological diagnosis of juvenile rheumatoid arthritis (JRA) is difficult, as classical 19S IgM rheumatoid factors (RF) as detected by the latex fixation test (LFT) are usually found in the sera of only 5-10% of JRA children, as compared with 80% of rheumatoid arthritis adults (RA).

Hidden 19S IgM rheumatoid factors (hidden RF), i.e., 19S IgM RF that can be detected in the IgM containing fraction after acid gel filtration of the serum, are found in 59-68% of seronegative JRA patients.

This test correlates strongly with the disease activity in JRA patients, but it requires serum separation and is not available in most laboratories.

Antiperinuclear factor (APF) has been described in both seropositive and seronegative adult rheumatoid arthritis (RA) patients, but has not been thoroughly evaluated in JRA children Materials: The study was conducted on 76 patients, 58 JRA with mean age 12.7 ± 3.0 years and 18 SLE cases with mean age 10.3± 3.7 years.

The group of JRA was subdivided into 2 subgroups, JRA children (mean age 11.5 ±2.7 years) and group of adolescents JRA onset (mean age 18.3 ± 1.1 years).

Thirteen healthy children served as a control group who were matched for age and sex.

Methods: We tried to evaluate the diagnostic sensitivity and specificity of both antiperinuclear factor and hidden rheumatoid factor in JRA, and their correlation with the disease activity.

The levels of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) assessed the disease activity.

Sera from JRA children, systemic lupus erythematosus (SLE) and control children were tested for the presence of antiperinuclear factor with indirect immunofluorescence technique (IIF) and hidden rheumatoid factor was determined with Rose-Waaler test (RWT) in the IgM-containing fraction of serum after separation by ion exchange chromatography.

Results: Thirty-eight of 58 patients (65.5%) showed the presence of hidden 19S IgM RF in their serum, only 3/18 (16.6%) in SLE patients and none was found in the control group.

APF was found in 22/58 (38%) JRA, in 2/18 (11%) SLE and was not detected in the control group.

The disease activity correlated positively only with hidden RF titers in the evaluated group of JRA, while no positive correlation was found between APF and the disease activity parameters (erythrocyte sedimentation rate and C reactive protein).

As expected both hidden RF and APF tests showed high specificity of 90.3% and 93.5% respectively.

Conclusion: Although APF detection technique is indeed easier than hidden RF technique, the detection of APF alone will not be of a good diagnostic value in seronegative cases suspected to have JRA.