FricTest® is a validated, easy to use dermographometer for diagnosing patients with symptomatic dermographism (urticaria factitia) and for measuring their trigger thresholds and disease activity. The comb-like, four-pronged design of FricTest® 4.0, the newest version of this instrument, allows for simultaneous dermal stimulation with four tips of different lengths exerting four different provocation levels, from I (the weakest) to IV (the strongest). To obtain a response, FricTest® is placed vertically so that the four tips are touching the skin, and then stroked once with moderate pressure across the width of the volar surface of the forearm (or the patient´s back) for a distance of approximately 6 centimeters. A positive response is defined by a palpable weal of ≥ 3 mm in width (the diameter of FricTest® tips) at 10 min after provocation. Positive test responses to provocation with the longest FricTest® tip provocation level IV) confirm the presence of symptomatic dermographism.
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