Background Antikeratin antibodies (AKA) have been described as the most specific serologic markers of RA. However, whether these antibodies can identify a particular RA population it remains controversial.
Objectives To compare the immunogenetic features (HLA-DRB1 and TNF-a polymorphism) and radiological severity of a group of patients with early RA, according to the presence or not of AKA.
Methods 65 patients with early RA (48F/17M, mean age: 50 ± 14 y, mean disease duration 15 ± 12 mo, RF+:71%) were genotyped for HLA-DRB1 and TNF-a alleles. Hands and feet x-ray were taken at entry and then yearly during follow-up. The Larsen method was used to assess radiographic damage. AKA was determined by immunofluorescence using a modified Young method (sensitivity/specificity 60.2%/98.3%).
Results AKA were present in the sera of 34 patients (prevalence of 52.3%). RF was more frequently found in AKA+ patients than in those without (85.3% vs. 54.8%; p = 0.007). No differences were observed according to the shared epitope and the frequency of HLA-DR4. The different TNF-a polymorphisms were equally distributed in AKA positive and negative populations. No significative radiological differences (presence of erosive disease and Larsen score) were observed at study entry between both populations. A trend to a more progressive radiological damage was observed at the end of follow-up.(32 ± 6 mo) in those patients with AKA, although the differences were no significative (Larsen score of 6.1 ± 4.3 in AKA(+) vs. 4.5 ± 5.5 in AKA (-). This trend is also observed when only RF positive patients were evaluated.
Conclusion These results indicate that AKA cannot identify a distinct immunogenetic subgroup in Spanish reumatoid population. The role of AKA as a possible marker of a more aggressive joint disease merits further investigation.
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