Piloting Photographic Photonic Patch Testing: Pioneering Equitable Diagnosis of Contact Dermatitis

ABSTRACT

Objectives: Due to restricted access to cutaneous patch testing (PT) during the SARS-CoV-2 pandemic innovative strategies were necessary to promote equitable healthcare. Photonics generates, detects and manipulates physical light (photons) which can assess blood-flow in a clinical photograph and potentially act as a surrogate marker for cutaneous inflammation. We wished to assess if clinical photography and photonic image analysis could improve the virtual interpretation of PT results. Methods: PT photographs of 30 consecutive patients were taken using a 40- megapixel colour camera contemporaneous to PT assessment by study investigators. Photographs were then analysed using HyperCube using Principal Component Analysis (PCA), a technique used to reduce the dimensionality of datasets. Photonic images were then examined to determine a combination of variables or colour patterns indicating a positive result. Results: Thirty patients were recruited from September-November 2020. Two blinded investigators determined whether the results were positive, ?positive, irritant or other. Photonic, photographic and clinical results were compared. Initial blinded photonic evaluation captured 40% of positive PT while photographic assessment captured 51%. Unblinded evaluation captured 90% of both PCA and clinically positive results. Conclusions: The SARS-CoV-2 pandemic catalysed many changes in healthcare delivery and introduced opportunities to produce patient centred care. This pilot study employs innovative technology to improve rural accessibility to PT, promote inclusivity and reduce carbon emissions by reducing patient travel. Further development is necessary as while PCAanalysis of digital images improves pick-up of positive PTvirtually it remains inferior to face-to-face assessment. Multispectral imaging has the potential to expand the range of wavelengths further.