A 30-year-old man presents with haemolytic anaemia (Hb 7.2 g/dL), jaundice, and episodic dark urine after infections and medications. G6PD assay during crisis shows borderline low value. What is the most appropriate next step to confirm G6PD deficiency?
- A Repeat G6PD assay 2–3 months after haemolytic episode resolution ✓
- B Heinz body preparation
- C HPLC haemoglobin analysis
- D Direct Coombs test
Correct answer: A. Repeat G6PD assay 2–3 months after haemolytic episode resolution
Explanation
G6PD activity is measured in red blood cells; during an acute haemolytic episode, the oldest (most G6PD-deficient) red cells are preferentially haemolysed, leaving a younger reticulocyte-rich population with higher G6PD activity. A quantitative G6PD assay measured during crisis may therefore give a falsely borderline or normal result. The assay should be repeated 2–3 months after complete resolution of haemolysis when the RBC population is stable, to reliably identify deficiency. DNA mutation analysis is the definitive test when the enzyme assay is inconclusive.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.