Value of nailfold capillaroscopy in the classification of the systemic sclerosis pattern

Nailfold videocapillaroscopy (NVC) is the gold-standard to identify scleroderma patterns. Our aim was to establish the minimum requirements; number of fingers, length of nailbed samples, location of nailbed areas, to diagnose the existence of systemic sclerosis patterns (SSc-P) and further identify non-SSc-P and SSc-P subtypes reliably.

NVCs were taken during routine explorations by capillaroscopists from 12 hospitals, who made four diagnosis per patient according to the examination of the following: 32 images (4 images/finger, mean 59.43mm); 16 images (2 medial images/finger [mean 29.28mm]); 8 images (1 medial image/finger [mean 14.50mm]); 4 images (1 medial image per middle fingers [mean 7.22mm]). Diagnosis matches and discrepancies considering 32 versus 16, 8 or 4 images, were calculated, with the goal of estimating the information loss when not covering the whole nailbed. The same analysis was performed using the CAPI-Score and CAPI-Detect algorithms.

A total of 2,387 NVCs were used. Disagreement in pattern assignment was 26.7%, 36.6% and 41.5% when the analysis was performed over 16, 8 or 4 images, respectively. When 16 images were used, 18.5% of expert observers changed their assigned pattern in 18.5% of cases from SSc-P to non-SSc-P, and >30% of patients diagnosed were assigned a different subtype. Although to a lesser extent, diagnosis discrepancies were observed when CAPI-Score and CAPI-Detect algorithms were applied.

All fingers but thumbs have to be considered to identify scleroderma patterns accurately. Four nailbed areas in the analysis demonstrated to be superior than using a partial sample.