An evaluation of two novel capillaroscopy techniques in suspected scleroderma-spectrum disorders: A single-centre cross-sectional study

Abstract

Objectives: The primary aim was to evaluate the diagnostic performance of digital photographs taken with a smartphone camera using both a lens attachment and, separately, a dermatoscope. The secondary aims were to assess the influence of prior capillaroscopy experience and familiarity with the novel techniques on diagnostic accuracy. Methods: All patients referred for capillaroscopy between May 2016 and January 2017 were eligible for inclusion. Nailfolds were classified by widefield microscopy before proceeding double-blinded to nailfold photography using both novel techniques. Randomised photographs were assessed by three independent investigators and results were compared to widefield microscopy. Sensitivity, specificity, inter- and intra-observer variability were calculated. Results: Sixty-five participants contributed over 1000 digital photographs for assessment. The ‘smartphone-lens’ technique performed with moderate sensitivity (65%; 58–72) and high specificity (90%; 84–96). The ‘smartphone-dermatoscope’ technique performed with higher sensitivity (74%; 66–82) and excellent specificity (95%; 88–100) and was used more accurately by a novice. Prior assessor experience with nailfold capillaroscopy in general and prior experience with the novel techniques positively modulated the diagnostic accuracy. Conclusion: New technologies, in this case utilising a smartphone camera, could help to improve accessibility to nailfold capillaroscopy, an important diagnostic tool and putative biomarker in scleroderma-spectrum disorders, whilst retaining accurate results.