A 20-year-old man of Mediterranean descent presents with jaundice and dark urine 2 days after starting trimethoprim-sulfamethoxazole for a urinary tract infection. Peripheral smear shows bite cells and blister cells. Which statement about G6PD testing is correct?
- A G6PD level should be measured during the hemolytic crisis for accurate diagnosis
- B G6PD level may be falsely normal during hemolysis because reticulocytes have higher enzyme levels ✓
- C The methemoglobin reduction test is the gold standard confirmatory test
- D Heinz bodies are best visualized with Wright-Giemsa stain
Correct answer: B. G6PD level may be falsely normal during hemolysis because reticulocytes have higher enzyme levels
Explanation
During acute hemolysis, older enzyme-deficient RBCs are destroyed, and the remaining young reticulocytes have near-normal G6PD levels, potentially masking the deficiency. Testing should be repeated 2-3 months after the crisis or during a stable period. Heinz bodies require supravital staining with brilliant cresyl blue, not Wright-Giemsa. Quantitative spectrophotometric assay, not the methemoglobin reduction test, is the gold standard.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.