Before initiating omalizumab in a patient with severe allergic asthma, which two parameters must be measured to determine the appropriate dose?

• A Serum total IgE level and body weight ✓
• B Body weight and peripheral eosinophil count
• C FeNO and serum specific IgE titre
• D Blood group and total IgG level

Explanation

Omalizumab is a humanised monoclonal antibody that binds free IgE at the same site as the Fc epsilon RI receptor, preventing mast cell sensitisation. Dosing tables are based on baseline serum total IgE concentration and body weight, since the amount of antibody required depends on circulating IgE mass. Eosinophil counts guide IL-5 directed biologics such as mepolizumab, not omalizumab. FeNO is used to assess type 2 inflammation but does not set the omalizumab dose.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.