Diagnostic and prognostic values of antikeratin antibodies (AKA) and collagen III propeptides (PIIINP) in juvenile rheumatoid arthritis

Abstract

Background: The need for specific and sensitive diagnostic as well as prognostic markers for juvenile rheumatoid arthritis (JRA) has urged  scientific research toward this field.
Objective: We sought to assess the diagnostic and prognostic values of serum and synovial fluid collagen III propeptides (PIIINP) and antikeratin antibodies(AKA) in JRA.
Methods :Thirty-one JRA patients with a mean age of 10.6±4.2 years were enrolled in the study. They were compared to 10 SLE patients with arthritis and 15 age and sex matched healthy children as control groups. All  patients were subjected at enrollment to laboratory evaluation by CBC,  ESR, CRP, serum PIIINP and AKA. Patients with knee effusion were  subjected to AKA and PIIINP analysis in their synovial fluid samples. Clinical evaluation was done by examination of joint swelling, tenderness and limitation of movement scores. Also, radiological evaluation by plain X-ray films for hands, knees and feet using modified Larsen score (MLS) was performed. Laboratory, clinical and radiological evaluation methods were re-performed after 3 months of proper treatment. A third radiological evaluation was done one year after the first evaluation.
Results: Serum PIIINP was significantly elevated in JRA patients  (12.8±8.7) ìg/L in comparison to healthy controls (7.0±1.9 ìg/L, p<0.05). However, no significant difference was observed when compared to SLE patients. Reduction of serum PIIINP was observed after 3 months of treatment with no significant difference between JRA patients (10.5±8.8 ìg/L) and the healthy controls. Synovial fluid PIIINP (56.4±6.6 ìg/L) was significantly higher than that of the serum (p<0.05). Neither serum nor synovial fluid PIIINP correlated with any of the laboratory, clinical or radiological parameters. The serum AKA positivity rate was significantly higher in JRA patients (77% at the study onset and 90% after three months) as compared to the control group (7%, p<0.001). Serum AKA values recorded a sensitivity, specificity and diagnostic efficiency in JRA patients of 77%, 93% and 83% at the study onset. These values increased after 3 months to 90%, 93% and 91% respectively. Synovial AKA levels displayed no significant difference in comparison to that of the serum.
Conclusion :AKA is a specific and sensitive diagnostic marker for JRA. Meanwhile, PIIINP was significantly elevated during JRA disease activity particularly in the synovial fluid. Neither AKA nor PIIINP proved to have prognostic values in JRA.

Key words: juvenile rheumatoid, arthritis, antikeratin antibodies, collagen III propeptides, SLE.