PD10 Retrospective analysis of phototesting wavelength sensitivity to optimize patient coverage and phototesting efficiency

Abstract Narrow-waveband phototesting is considered the gold standard for diagnosing photosensitive disorders. It spans the solar spectrum covering ultraviolet (UV)B, UVA and visible light wavelengths, typically ranging from 300 nm to 600 nm in all UK phototesting centres (Ibbotson SH, Allan D, Dawe RS et al. Photodiagnostic services in the UK and Republic of Ireland: a British Photodermatology Group workshop report. J Eur Acad Dermatol Venereol 2021; 35: 2448–55). Sensitivity to specific wavelengths varies depending on the individual and their condition. However, narrow-waveband phototesting is currently limited to tertiary centres and can be time consuming and resource intensive. This study aimed to identify the most effective phototesting waveband combination that would cover the majority of photosensitive patients and could potentially serve as a screening tool. A retrospective review was conducted of abnormal monochromator phototest results from 2021 to 2024 in a UK national photobiology unit. The study assessed the following phototesting wavebands: 305 ± 5 nm (UVB), 335 ± 27 nm (UVA), 365 ± 27 nm (UVA), 400 ± 27 nm (visible) and 430 ± 27 nm (visible). In total 217 abnormal monochromator phototest results were included in this study. Among these, 35 (16%) were of abnormal immediate sensitivity, while 182 (84%) showed abnormal delayed sensitivity. The Table summarizes the percentage of photosensitive individuals who exhibited heightened sensitivity to various phototesting wavebands and their combinations. In conclusion, combining multiple phototesting wavebands significantly improves detection rates of photosensitive individuals. Almost 90% of photosensitivity would be detected if screening with UVB and UVA wavelengths (305 nm and 365 nm), which could be improved to 96% by combing with 400 nm. Limited-wavelength phototesting has the potential to be a useful screening approach for photosensitivity.TablePositive phototesting in 217 individualsTesting wavebandPositive results, n (%)305 nm (UVB) only138 (64)335 nm (UVA) only160 (74)365 nm (UVA) only154 (71)400 nm (visible) only85 (39)430 nm (visible) only35 (16)305 nm + 335 nm (UVB + UVA)183 (84)305 nm + 365 nm (UVB + UVA)193 (89)335 nm + 365 nm (UVA)189 (87)400 nm + 430 nm (visible)111 (51)305 nm + 335 nm + 400 nm (UVB + UVA + visible)203 (94)305 nm + 365 nm + 400 nm (UVB + UVA + visible)208 (96)305 nm + 335 nm + 430 nm (UVB + UVA + visible)198 (91)305 nm + 365 nm + 430 nm (UVB + UVA + visible)202 (93)305 nm + 335 nm + 365 nm + 400nm (UVB + UVA + visible)212 (98)UV, ultraviolet.