Can nailfold videocapillaroscopy images be interpreted reliably by different observers? Results of an inter-reader and intra-reader exercise among rheumatologists with different experience in this field.

Nailfold videocapillaroscopy (VCP) allows non-invasive assessment of the microcirculation. Adequate training in this field is relevant for rheumatologists. There is increasing evidence of the reliability of VCP findings among different readers. Objective: To evaluate inter- and intra-reader agreement of rheumatologists to identify normal images and systemic sclerosis (SSc) patterns on VCP ("early," "active," and "late" proposed by Cutolo et al.). Thirteen rheumatologists with different experience in nailfold VCP received training to standardize reading criteria. They rated 60 VCP images from healthy and SSc patients at baseline and 4 weeks later, using an electronic platform. The reading of an expert was considered the gold standard. Data were analyzed using Cohen's kappa for concordance and Student's t test and ANOVA to compare kappa means for inter-reader, intra-reader, and inter-pattern readings. Mean inter-reader and intra-reader kappa were 0.45 and 0.49, respectively, (moderate agreement). Kappa scores were higher among experienced vs inexperienced readers (inter-reader kappa 0.58 vs 0.34, p = 0.001, intra-reader kappa 0.65 vs 0.37, p = 0.01). Agreement was substantial (kappa = 0.61) for the identification of normal vs abnormal images and higher for the identification of active (0.48, p = 0.009) and late SSc patterns (0.56, p = 0.008) than for the early SSc pattern (0.35, p = 0.003). There is moderate agreement among rheumatologists for the identification of SSc videocapillaroscopy patterns (higher among experienced rheumatologists) and substantial agreement, regardless of previous experience in VCP, in the identification of normal and abnormal images. Agreement for the identification of active and late patterns is higher than for the early pattern.