The use of Reflectance Confocal Microscopy to diagnose Basal Cell Carcinoma in the United Kingdom: A Prospective Observational Trial at a Single Centre

Background: Previous work with Reflectance Confocal Microscopy (RCM) imaging has shown high sensitivity and specificity for Basal Cell Carcinoma (BCC), but to date there have been few studies on a UK cohort.

Objectives: The study hypothesised that RCM could be used prospectively to accurately diagnose BCC in a private UK secondary care, single clinician setting. The study assessed the potential for RCM to be used as a routine diagnostic procedure.

Methods: 522 lesions were recruited prospectively where BCC featured in the differential diagnosis after clinical examination. 78 were subsequently excluded. Imaging used the arm-mounted confocal microscope unless access was restricted and required the handheld probe. The likelihood of BCC was scored for each modality, each diagnosis building on the last. Histology was assessed by a single blinded histopathologist [JJ].

Results: 444 lesions from 326 patients were included in the analysis, including 327 BCCs. Median maximum diameter was 6 mm. The sensitivity and specificity for BCC was 69.42% (64.11% to 74.37%) and 52.99% (43.55% to 62.28%) for clinical examination alone; 91.77% (88.25% to 94.51%) and 41.03% (32.02% to 50.50%) plus dermoscopy; 98.78% (96.91% to 99.67%) and 85.47% (77.76% to 91.30%) plus RCM. For RCM PPV was 95.01% (92.14% to 97.07%) and NPV was 96.15% (90.44% to 98.94%). Area under the curve increased from 0.61 to 0.66 to 0.92 as modalities were added.

Conclusion: This study demonstrates that RCM can, reliably and quickly, diagnose BCC, and that the addition of RCM to dermoscopy permits higher diagnostic accuracy for BCC in the UK. The specificity and sensitivity of the RCM diagnosis did not alter significantly with experience, reflecting the ease and speed of acquiring the skill.

Clinical trial registration: NCT03509415.