Re-evaluation of nailfold capillaroscopy in discriminating primary from secondary Raynaud's phenomenon and in predicting systemic sclerosis: a randomised observational prospective cohort study.

BACKGROUND

Primary Raynaud's phenomenon (pRP) is difficult to distinguish from secondary (sRP). Although nailfold capillaroscopy (NFC) may detect early alterations, no universal criteria yet discriminate between pRP from sRP.

OBJECTIVES

To create and validate two NFC scores that could distinguish pRP from sRP and that could predict systemic sclerosis (SSc), respectively.

METHODS

We performed NFC on two separate cohorts with isolated RP, and recorded number of capillaries per field, enlarged/giant capillaries, crossed/bizarre patterns, microhemorrhages, neoangiogenesis, rarefaction, edema, blood flow velocity, stasis. By multivariate regression analysis, we evaluated the adjusted prognostic role of these features in a derivation cohort of 656 patients. Results were used to construct algorithm-based prognostic scores (A and B). These scores were then tested on a confirmation cohort of 219 patients.

RESULTS

Score A was unable to discriminate sRP from pRP (low negative predictive values with high positive predictive values for any cut-point); score B was unable to discriminate progression to SSc or a SSc-spectrum disorder (low positive predictive values with high negative predictive values for lower cut-points).

CONCLUSION

NFC patterns, believed as specific, showed low discriminatory power and on their own are unable to reliably discriminate sRP from pRP or predict evolution to SSc.