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CSU Investigations — SCE Dermatology MCQ

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ModerateInflammatory DermatosesCSU InvestigationsSCE Dermatology

A 40-year-old woman has severe chronic spontaneous urticaria. She has failed maximum antihistamines. Before starting Omalizumab, what baseline investigations are recommended?

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Correct answer: A — Baseline IgE level, FBC with differential, CRP/ESR, thyroid function (anti-thyroid antibodies), and consideration of autoimmune screen

Before starting Omalizumab for CSU, recommended baseline investigations include: total IgE (baseline for monitoring — though Omalizumab dosing in CSU is fixed, unlike asthma), FBC with eosinophil count, CRP/ESR (to exclude systemic inflammation), thyroid function tests and anti-thyroid peroxidase antibodies (autoimmune thyroid disease is associated with CSU in approximately 10-20%), ANA if clinically indicated, complement levels (C3, C4 — to exclude hypocomplementaemic urticarial vasculitis), and D-dimer (may predict antihistamine response). Skin biopsy should be performed if urticarial vasculitis is suspected. Tryptase baseline excludes mastocytosis. These investigations also help classify CSU subtype and guide prognosis.

Reference: EAACI/GA²LEN 2022; BAD; NICE TA339