Background/Purpose:

Nailfold capillaroscopy is a non-invasive, sensitive and specific technique used in the diagnosis of scleroderma-spectrum disorders. Abnormalities predict progression from Raynauds phenomenon to connective tissue disease, sometimes years in advance, as well as serious complications such as pulmonary hypertension. Its inclusion in the most recent diagnostic criteria for systemic sclerosis enable them to perform better to identify patients with early systemic sclerosis in particular, important for prognostication, risk stratification, screening regimens and hopefully, in future, therapeutic intervention.

The current gold standard techniques are nailfold videocapillaroscopy and widefield microscopy. The equipment required for both remains expensive and relatively inaccessible, typically only available in centers with a special interest. Novel approaches utilizing new technologies may help improve accessibility to the wider rheumatology community.  

We sought to evaluate the novel combination of a smartphone digital camera with two devices, a commercially produced lens attachment and a dermatoscope, with both techniques offering the possibility of a rapid bedside evaluation at a fraction of the cost of other techniques.

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:

This was a single-center cross-sectional study. All patients referred for capillaroscopy between May 2016 and January 2017 were eligible for inclusion.  Patients nailfolds were classified by widefield microscopy before proceeding, double-blinded, to have their nailfolds photographed using both novel techniques. Randomized photographs were assessed after the completion of enrolment by three independent investigators. Sensitivity, specificity, inter- and intra-observer variability were calculated.

Results:

65 participants contributed 1040 digital photographs for independent assessment by three investigators. 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 improve accessibility to nailfold capillaroscopy, an important diagnostic tool and putative biomarker in scleroderma-spectrum disorders, whilst retaining accurate results.