Capillary loss reflects disease activity and prognosis in patients with systemic sclerosis

Capillary density on nailfold capillaroscopy (NFC) is considered a promising instrument for assessing disease characteristics in patients with systemic sclerosis (SSc), however, there is no agreement yet over how to analyze and interpret the results. The objective of this study was to investigate the possible associations of the mean number of capillaries with disease characteristics, disease activity [measured by the European Scleroderma Study Group (EScSG) disease activity score] and survival in a single-center cohort of patients with SSc. Sixty-eight patients were included; 54 had follow-up at 6 months. Thirty-two images per patient were assessed independently by two raters, scoring the mean number of capillaries in all fingers (N), in the 3rd finger of the dominant hand (dN₃) and in the 4th finger of the non-dominant hand (ndN₄) for each patient. NFC 'early', 'active' and 'late' patterns were also assessed. Two thousand and seventy-six images were scored at baseline, 1,728 at follow-up. Baseline N was median (IQR) 5.1 (2.7) for rater 1, and 4.9 (1.7) for rater 2, respectively. N was significantly lower in patients with a history of digital ulcers (DUs), vs. those who never had DUs 4.8 (1.4) vs. 6.4 (3.1), P=0.016. A lower N was associated with higher disease activity at baseline and follow-up (linear regression adjusted for age, sex and history of DUs). A lower ndN₄ was associated with increased mortality (logistic regression adjusted for age and sex). In conclusion, in patients with SSc, a lower mean number of capillaries assessed by NFC was associated with higher disease activity after 6 months of follow-up and with shorter survival.