Optoacoustic mesoscopy shows potential to increase accuracy of allergy patch testing

Abstract

BackgroundDifferentiation between irritant and allergic skin reactions in epicutaneous patch testing is based largely on subjective clinical criteria, with the risk of high intraobserver and interobserver variability. Novel dermatological imaging using optoacoustic mesoscopy allows quantitative three‐dimensional assessment of microvascular biomarkers.ObjectivesWe investigated the potential of optoacoustic imaging to improve the precision of patch test evaluation.MethodsSixty‐nine test reactions and 48 healthy skin sections in 52 patients with suspected type IV allergy were examined using raster‐scan optoacoustic mesoscopy.ResultsWe 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 < .05), as well as lower ratio of low‐ to high‐frequency acoustic signals (1.6 ± 0.5 vs 2.0 ± 0.6, P < .05). Allergic reactions graded “++” showed higher vessel fragmentation than reactions graded “+” (25.4 ± 13.2 vs 17.1 ± 6.5 fragments/100 pixels2; P < .05). 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% confidence interval 0.64‐0.91), reaching a sensitivity of 81% and specificity of 63%.ConclusionsOptoacoustic mesoscopy shows potential to help in differentiating between allergic and irritant test reactions based on novel biomarkers that may reflect vasodilation, vessel tortuosity, and edema.

Optical coherence tomography for patch test grading: A prospective study on its use for noninvasive diagnosis of allergic contact dermatitis

“…Dermoscopy is cheap and available worldwide; pilot studies correlated erythema, vesicles, orange‐yellowish patchy areas, and vessels with allergic reactions compared to irritant reactions; nonetheless, additional studies on doubtful reactions are needed 15,16 . Among further noninvasive diagnostic tools, RCM, OCT, and optoacoustic mesoscopy showed the most promising results 9‐14,24 . However, RCM is more time consuming than OCT and does not provide an immediate, intuitive comparison with histology in nonexpert physicians.…”

“…However, RCM is more time consuming than OCT and does not provide an immediate, intuitive comparison with histology in nonexpert physicians. Optoacoustic mesoscopy was able to associate a higher fragmentation of skin vasculature and a lower ratio of low‐to‐high frequency acoustic signals to allergic reactions compared to irritant reactions in a pilot study 24 ; however, use of the device is still limited to clinical research. The few studies with OCT reported to date were based on a small number of samples and did not systematically include irritant controls and unclear reactions.…”

Seeing through the Skin: Photoacoustic Tomography of Skin Vasculature and Beyond

“…In fact, positive tests were only reproducible in 86% of cases, and the reproducibility was far lower for mild reactions (Lazzarini et al, 2013). Using RSOM, however, Hindelang et al were able to distinguish mild (+) and strong (++) reactions to patch-tested allergens using vessel fragmentation and ratio of low-to high-frequency content as biomarkers (Hindelang et al, 2020). While Hindelang et al are one of the first to explore PAT in patch testing, their results are promising for future applications of PAT to diagnose this disease.…”

Optoacoustic imaging of the skin

“…for the detection of glucose and glycation end products in the skin. [143][144][145] Other applications include assessment of ageing effects, 146,147 allergy patch testing 148 or estimation of imaging metrics in Fitzpatrick skin. 149 New technical advances are expected to enhance imaging capabilities thus potentially defining new areas of application.…”