Pathology · patient case question
Which laboratory test is most important to obtain before continuing her care given the methotrexate and adalimumab combination?
Patient case: Joints, immunosuppression and a sore mouth
demo: 58-year-old female
chief: Painful mouth ulcers that appeared over the last three weeks and are interfering with eating.
history: Seropositive rheumatoid arthritis for eleven years, currently in low disease activity. She was also treated for latent tuberculosis before starting her biologic.
meds: Methotrexate 20 mg weekly with folic acid. Adalimumab (Humira) every other week. She completed a nine-month course of isoniazid last year.
findings: Multiple shallow, painful ulcers on the buccal mucosa and lateral tongue with erythematous halos. No vesicles. Mild pallor of the conjunctivae.
Show answer and explanation
Correct answer: B. Serum creatinine with a complete blood count and liver enzymes
- A. Thyroid function is not affected by methotrexate or adalimumab and is not part of routine monitoring for them.
- B. Correct. Methotrexate is cleared renally, so a rising creatinine causes the drug to accumulate and become toxic. Standard monitoring pairs renal function with a complete blood count, because methotrexate suppresses marrow and causes macrocytic anaemia and neutropenia, and with liver enzymes because of hepatotoxicity.
- C. Amylase relates to pancreatic and salivary pathology and has no role in monitoring either of these agents.
- D. A lipid panel is a cardiovascular risk tool, not a safety monitor for these drugs.
Note: The recall keyed this simply as 'creatinine test.' That is defensible because renal clearance governs methotrexate toxicity, but the real-world panel is creatinine plus CBC plus liver enzymes, and for a patient on a TNF inhibitor also a check for reactivated infection.