When is G6PD testing most reliable?

When is G6PD testing most reliable?

• A. After the acute hemolytic episode resolves (1–2 weeks)
• B. During the acute hemolysis
• C. At birth only
• D. Only by direct gene sequencing

Answer: (A)

G6PD testing is most reliable after the acute hemolytic episode has resolved because the test measures enzyme activity in red cells, and the composition of those cells shifts during hemolysis. During an episode, older G6PD-deficient cells are destroyed, leaving a higher proportion of younger reticulocytes that have relatively higher G6PD activity. This can mask the deficiency and yield a falsely normal result. Once the acute event passes and the red cell population returns to baseline, the measured enzyme activity more accurately reflects the true G6PD status. Testing during an acute attack is unreliable for this reason, and testing at birth is not consistently reliable due to ongoing reticulocytosis and perinatal factors; direct gene sequencing isn’t needed for initial evaluation because enzyme activity is the standard first-line test.

G6PD testing is most reliable after the acute hemolytic episode has resolved because the test measures enzyme activity in red cells, and the composition of those cells shifts during hemolysis. During an episode, older G6PD-deficient cells are destroyed, leaving a higher proportion of younger reticulocytes that have relatively higher G6PD activity. This can mask the deficiency and yield a falsely normal result. Once the acute event passes and the red cell population returns to baseline, the measured enzyme activity more accurately reflects the true G6PD status. Testing during an acute attack is unreliable for this reason, and testing at birth is not consistently reliable due to ongoing reticulocytosis and perinatal factors; direct gene sequencing isn’t needed for initial evaluation because enzyme activity is the standard first-line test.