Statistical reappraisal of the clinical significance of nail beading in rheumatoid arthritis.

Nail beading has previously been reported as an accompaniment of rheumatoid arthritis. In order to assess the clinical significance of this form of nychodystrophy the fingernails and toenails of 119 patients with rheumatoid arthritis and an equal number of control subjects were studied. Analysis of data based on 4642 nails indicates that the presence of a global pattern of beading (i.e. greater than or equal to 50% involvement of the nail area) on the surface of at least six fingernails or four toenails is highly suggestive of underlying rheumatoid disease. The positive predictive value of these configurations is in the order of 95%. Nail beading, however, is infrequent in early disease and therefore its diagnostic value is limited. Although there is a strong association between nail beading and rheumatoid arthritis, the aetiology and prognostic implications of this clinical sign remain obscure.