A multicentre study on the reliability of qualitative and quantitative nail-fold videocapillaroscopy assessment

Objective. To investigate the inter-and intra-observer reliability of both qualitative and quantitative parameters used in the assessment of nail-fold capillaroscopy images. Methods. Fifty mosaic nail-fold images of healthy controls (n = 10), patients with primary RP (n = 10) and SSc (n = 30) were assessed in random order by two blinded observers on two occasions at centres in Sweden, UK and The Netherlands. Each image was therefore scored by six observers twice. Results. Inter- and intra-observer reliability of quantitative parameters showed substantial to almost perfect agreement [inter- and intra-observer weighted kappa's for the number of widened capillaries was 0.75 and 0.87 and giant capillaries was 0.84 and 0.92, intra-class correlation coefficients (ICCs) for capillary density was 0.87 and 0.92 and total loop width was 0.94 and 0.98, respectively]. Qualitative parameters including architecture, avascularity, haemorrhage, crossed, ramified and bushy capillaries showed moderate to substantial inter-observer reproducibility (weighted kappa ranging from 0.47 to 0.73), and substantial intra-observer repeatability (weighted kappa ranging from 0.71 to 0.80), whereas the scoring of tortuous and bizarre capillaries showed poor inter-observer and substantial intra-observer agreement (inter-observer weighted kappa's was 0.39 and 0.21 and intra-observer weighted kappa's was 0.68 and 0.76, respectively). Conclusion. All quantitative and certain qualitative parameters are highly reliable in terms of inter- and intra-observer agreement. A combination of parameters with the highest reliability should be incorporated into future capillaroscopic scoring systems in studies of prediction and monitoring of SSc spectrum disorders.