Longer itch persistence, diminished histamine-induced flare may support diagnosis
MONDAY, Aug. 8, 2016 (HealthDay News) — Topical cowhage provocation and skin prick testing with histamine can diagnose atopic dermatitis (AD), according to a study published online July 29 in Allergy.
Tomasz Hawro, M.D., from Charité-Universitätsmedizin Berlin, and colleagues subjected 22 AD patients and 18 healthy controls to topical cowhage provocation and skin prick testing with histamine. The authors examined the differences in the quality, intensity, and persistence of itch, and in wheal diameter, volume, flare size, and intensity.
The researchers found that patients with AD had significantly smaller histamine-induced flares and markedly longer itch persistence after provocation with cowhage versus healthy controls (P < 0.01). Both parameters showed good diagnostic properties for AD, with area under the receiver operating characteristic curves of 0.78 and 0.80, respectively. Reliable thresholds for AD diagnosis were persistence of cowhage-induced itch for at least 30 minutes and a histamine-induced flare of less than 2 cm. The sensitivity and specificity of diagnosing AD increased to 91 and 94 percent, respectively, if combinations of the results of both tests were used.
“The clinical benefit of cowhage and histamine skin provocation tests should be investigated in further studies,” the authors write.
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