Quantification of cutaneous oedema in patch test reactions by measurement of skin thickness with high‐frequency pulsed ultrasound

Publisher Website
Google Scholar
Abstract
Doubtful and positive patch test readings (?+21, +23, ++18, +++7) in 15 contact dermatitis patients were studied by measurement of skin thickness as an expression of allergic edema. Exposed skin was compared with a regional control. Skin thickness was measured by 15 MHz pulsed ultrasound (A-scan) to 0.1 mm accuracy. The ?+, +, ++ and +++ reactions could be separated by measurements of absolute difference in thickness (P < 0.001, P < 0.001, P < 0.02) between exposed and non-exposed skin; the mean increases were 0.14, 0.49, 0.93 and 1.37 mm. The ?+, + and ++ reactions, but not the +++ reactions, could also be separated by measurements of relative increase in skin thickness (P < 0.001, P < 0.001, n.s. [not significant]); the mean increases were 7, 25, 50 and 55%. The normal thickness of the skin of the back increased (P < 0.02) in patients with +++ reactions only. Thus, the high-frequency ultrasound method is suitable for quantification of doubtful and positive patch test reactions. The +++ reactions are probably explained by the normal thick skin of the back, and they need no separate recording in patch testing. Standards of increase in skin thickness in doubtful and positive patch tests are defined: absolute increase (mm) was ?+ .ltoreq. 0.2; +0.3-0.7; ++0.8-1.3 (+++ .gtoreq. 1.4); relative increases were ?+ < 15%; +15-45%, ++(+++ included) > 45%.