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

Abstract

69 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 oedema. 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 less than 0.001, p less than 0.001, p less than 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 less than 0.001, p less than 0.001, n.s.); the mean increases were 7%, 25%, 50% and 55%. The normal thickness of the skin of the back was shown to have increased (p less than 0.02) in patients with reactions only. It is concluded that 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 ?+ less than or equal to 0.2; +0.3-0.7; ++0.8-1.3 ( greater than or equal to 1.4); relative increases were ?+ less than 15%; +15-45%, ++ ( included) greater than 45%.

Skin Irritation and Sensitization: Mechanisms and New Approaches for Risk Assessment

“…A number of studies apply ultrasound evaluation of the skin reaction elicited by irritant exposure [111][112][113] . The basis of using this method is the changes of skin thickness due to dermal oedema which were initially registered by A-mode ultrasound scanning [113] . Introducing the twodimensional B-mode ultrasound technique revealed more intimate changes in the epidermis [111,112] .…”

Bioengineering and the patch test

“…Serup et al (24) (Table 2), usmg a specially des1gned htgh-frequency pulsed ultrasound techmque, reported differentiatiOn of positive patch test reactiOns on the basts of skm thickness: doubtful reacttwns < 0.2 mm; + reactiOns 0.3-0. 7 mm; + + reactwns > 0.8 mm; + + and + + + reactions could be differentiated by the absolute mcrease m the skm thickness, but less significantly.…”

“…The naked (8) no correlatiOn with stronger reactwns (6,8) good quantification of erythema (17) artifacts could be produced positiomng the probe not helpful unless VIsible erythema IS detectable (20) difficult positionmg on the skm dimmution of edema with pressure more reliable than caliper differentiation withm ? +, + and + + reactwns (24) not all Irritants mcrease TEWL (33) good correlatiOn with SLS (33) sensitive to environmental conditions time consummg (compared to the eyes and fingers) storage of several data recorded by different operators eye still remams the simplest, qmckest and cheapest way to assess skm Irritancy, but LDV can detect mvisible changes of blood flow helpful m evaluatmg doubtful patch test reactiOns.…”

High-Frequency Ultrasound in the Evaluation of Pharmacological Effects on the Skin

“…Quantitative and more objective evaluation of patch test reactions becomes possible through the help of ultra- sound, e.g. a 15-MHz A-scan device, as demonstrated by Serup et al [21]: The ?+, +, ++ and +++ reactions can be separated by determining the difference in skin thickness between test sites and controls [21].…”

“…Since the clinical assessment of patch test reactions to a certain extent underlies subjective influences, the reading scale from ?+ to +++, suggested by the International Contact Dermatitis Research Group, is not automatically interpreted in the same way in different dermatological clinics [21]. Quantitative and more objective evaluation of patch test reactions becomes possible through the help of ultra- sound, e.g.…”