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

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.