Diagnostic value of nailfold capillaroscopy in suspected secondary Raynaud phenomenon: a cross-sectional analytical study

Abstract Background Nailfold capillaroscopy (NFC) is a widely used rheumatology tool for assessing Raynaud phenomenon (RP). Nonspecific abnormal findings observed through NFC may appear in patients with primary RP, suspected secondary RP, secondary RP, and healthy individuals. Differentiating between these findings remains a subject of ongoing research. This study aimed to describe capillaroscopic alterations in patients with suspected secondary RP and compare them with healthy subjects. Methodology This was a cross-sectional study. A total of 159 participants were included: 74 with suspected secondary RP and 85 healthy volunteers. NFC was performed with an emphasis on nonspecific abnormal findings. Results The overall population was predominantly female (63.5%). The median age was 42 in the suspected secondary RP group and 30 years in the healthy group. The number of tortuous capillaries, abnormal morphology, and dilated loops >30–50 μm were associated with suspected secondary RP (odds ratios: 1.14, 1.54, and 33.96, respectively). The number of tortuous capillaries showed the best discriminative performance for identifying suspected secondary RP (AUC: 0.84). The optimal cutoff point was ≥10 tortuous capillaries per examination, yielding 85% sensitivity and 70% specificity. Conclusion Among the nonspecific abnormal capillaroscopic findings, the number of tortuous capillaries and the presence of dilated capillary loops >30–50 μm showed the strongest association with suspected secondary RP compared with those in healthy individuals.