Which bedside test is used to confirm acquired cold urticaria?

• A Measurement of serum tryptase immediately after cold exposure
• B Temporal artery thermometry after cold water immersion
• C Intradermal histamine challenge
• D Application of an ice cube to forearm skin for 5 minutes, observing wheal formation on rewarming ✓

Explanation

The ice cube test is diagnostic: an ice cube held on the forearm for about 5 minutes produces an urticarial wheal as the skin rewarms. In patients with systemic features or onset in adulthood, cryoglobulins should be sought because secondary cold urticaria occurs with cryoglobulinaemia, hepatitis C infection and other conditions. Histamine challenges and tryptase measurement are not validated tests for cold urticaria.

Reference: Fitzpatrick's Dermatology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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