antikeratin antibodies As A Diagnostic Marker For Rheumatoid Arthritis: The Significance of The Laminated Fluorescence Pattern

1Manal H. Abbas, 1Mohamed Khaled M. Metwally, 1Magda Abd-Elmegid Amer and 2Magda Z. Kenawy.

1Rheumatology and Endocrinology units and 2Internal Medicine Department, Ain Shams University Hospitals, Cairo, Egypt.

Sera from 30 adult patients with rheumatoid arthritis (RA) with mean age of 40 ± 10.8 years, 8 patients with juvenile rheumatoid arthritis (JRA) with mean age of 10 ± 4.1 years and 41 non-RA arthritides (controls) with mean age of 39 ± 11.1 years were studied. The last group included patients with systemic lupus erythematosus, sjogren’s syndrome, mixed connective tissue diseases and progressive systemic sclerosis. Sera were tested for antikeratin antibodies (AKA) by indirect immunofluorescence (IIF) utilizing rat oesophagus as substrate. IgM rheumatoid factor(RF) was investigated in all sera by Rose-Waaler test (RWT). Anti-nuclear antibodies (ANA) were estimated by enzyme linked immunosorbent assay (ELISA). The immunofluorescence staining revealed 6 different patterns. Three patterns were associated with a characteristic fluorescence on the stratum corneum (stc) layer and the other three were mainly nuclear or cytoplasmic staining on the stratum spinosum (sts) and stratum basale (stb). Out of the three stc patterns only one showed a marked laminated fluorescence on stc layer and a concomitant weak cytoplasmic staining on sts and was present in 53.3% of RA patients as compared to 4.9% of non-RA arthritidis. This pattern was absent in all patients with seronegative JRA. The nuclear staining of the epithelial cell nucleus of sts and stb layers correlated with the presence of positive ANA. The mean RF titer of RA patients with positive AKA test was significantly elevated when compared to the mean RF titer of AKA negative ones (p < 0.001). It is concluded that the laminated fluorescence pattern of the AKA assay may be a valuable diagnostic marker for RA. A large scale study is recommended for evaluation of the sensitivity and specificity of the assay.