A patient taking methotrexate and adalimumab (Humira) is scheduled for oral surgery. Which laboratory test is most important preoperatively?

Correct answer: B. Complete blood count with differential

• A. Glucose would matter for a diabetic or a patient on systemic corticosteroids, but it is not the key test for methotrexate and a biologic.
• B. CORRECT. The dominant risk of this combination is MYELOSUPPRESSION and IMMUNOSUPPRESSION. Methotrexate is a folate antagonist that suppresses the bone marrow — producing leukopenia, thrombocytopenia and anaemia — and adalimumab is a TNF-alpha inhibitor that further impairs the response to infection. A COMPLETE BLOOD COUNT with differential gives you the neutrophil count (infection risk) and the platelet count (bleeding risk), which are the two numbers that determine whether surgery can safely proceed. Baseline renal function is also monitored, since methotrexate is renally cleared.
• C. PT/INR assesses the extrinsic coagulation pathway and is the test for warfarin or liver disease. Neither drug here acts on coagulation factors.
• D. Electrolytes are not the primary concern with these agents.

Note: ⚠️ The source keyed creatinine. Renal function IS monitored on methotrexate and is a reasonable secondary test, but CBC is the standard preoperative test for myelosuppression, and current perioperative guidance specifies baseline CBC and renal function. Worth discussing with the group. Note also that methotrexate is generally NOT stopped for dental surgery.