A 32-year-old woman with moderate-to-severe Crohn's disease (CDAI 280) has failed 5-ASA and two courses of steroids. Anti-TNF therapy (adalimumab) is initiated. After 14 weeks she has not achieved clinical remission (CDAI still 230). The MOST appropriate strategy according to current guidelines is:

• A Increase adalimumab dose to 80 mg every 2 weeks
• B Check serum adalimumab trough level and anti-drug antibody (ADA) titre to guide 'treat to target' optimisation ✓
• C Add 5-ASA for adjunctive mucosal healing
• D Switch immediately to vedolizumab without further assessment

Explanation

Therapeutic drug monitoring (TDM) is the evidence-based approach for anti-TNF non-response in IBD. Measuring trough adalimumab levels (target ≥7.5 μg/mL for clinical remission) and anti-drug antibodies (ADA) guides management: low drug level + high ADA = switch mechanism (e.g., vedolizumab); low drug level + low ADA = dose-intensify; adequate drug level + inadequate response = pharmacodynamic failure, switch mechanism. 'Test and treat' proactive TDM is superior to empirical dose escalation, as shown in the TAXIT and PRECISION trials.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.