Differentiation between irritant and allergic skin reactions in epicutaneous patch testing is based largely on subjective clinical criteria, with the risk of high intra- and interobserver variability. Novel dermatological imaging using optoacoustic mesoscopy allows quantitative three-dimensional assessment of microvascular biomarkers.
We investigated the potential of optoacoustic imaging to improve the precision of patch test evaluation by examining 69 test reactions and 48 healthy skin sections in 52 patients with suspected type-IV-allergy.
We identified biomarkers from the optoacoustic images. Allergic reactions were associated with higher fragmentation of skin vasculature than irritant reactions (19.5±9.7 vs. 14.3±3.7 fragments/100 pixels2 ; P≤.01), as well as lower ratio of low- to-high-frequency acoustic signals (1.6 ±0.5 vs. 2.0±0.6, P≤.0045). Allergic reactions graded “++” showed higher vessel fragmentation than reactions graded “+” (25.4±13.2 vs. 17.1±6.5 fragments/100 pixels2 ; P≤.0074). A linear model combining the biomarkers fragmentation and frequency ratio could differentiate allergic from irritant test reactions with an area under the receiving operator characteristic curve of 0.80 (95% CI 0.64-0.91), reaching a sensitivity of 81% and specificity of 63%.
Optoacoustic mesoscopy shows potential to help in differentiating allergic and irritant test reactions based on novel biomarkers that may reflect vasodilation, vessel tortuosity and edema.