Several histological studies suggest a vascular involvement in rheumatoid arthritis (RA). We evaluated morphological and functional changes of skin capillaries in patients with RA.
We studied capillary permeability by nailfold fluorescence videomicroscopy in patients with RA with and without systemic vasculitis to establish the sensitivity, specificity, and the prognostic value of the technique for the diagnosis of systemic rheumatoid vasculitis (SRV). Nine patients with SRV, 22 patients with active RA without signs of vasculitis, and 16 controls were evaluated.
No difference in conventional capillaroscopy was observed when we compared patients with SRV and RA. Using fluorescence videomicroscopy after intravenous injection of fluorescein sodium, we observed an increase of transcapillary dye diffusion in 9/9 patients with SRV, in 13/22 patients with RA without vasculitis and in 4/16 control patients. Our results give a sensitivity of 100% in SRV, a specificity of 44%, a positive predictive value of 34% and a negative predictive value of 100%.
Our present study points out the functional alteration of the capillary wall in patients with RA with or without vasculitis and suggests the usefulness of dynamic fluorescence nailfold capillaroscopy in patients with RA when systemic vasculitis is suspected, not as a diagnostic tool, but because of the high negative predictive value of the technique.