In a healthy adult, what is the typical upper limit for Hgb A2 fraction?

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Multiple Choice

In a healthy adult, what is the typical upper limit for Hgb A2 fraction?

HbA2 is a small delta-chain hemoglobin fraction that normally makes up only a few percent of total hemoglobin in adults. In a healthy adult the upper limit of HbA2 is typically about 3.5% of the total Hb. That’s why the best choice is the one stating “Under 3.5%.” In practice, the normal range is roughly 2.0–3.5%, so values above 3.5% can raise concern for conditions like beta-thalassemia trait, while values well below 3.5% are still within normal variation. The other options are not as close to the common reference range: 5% is higher than normal for most adults, 2% would be too low as an upper limit, and 10% is far outside the normal range.

HbA2 is a small delta-chain hemoglobin fraction that normally makes up only a few percent of total hemoglobin in adults. In a healthy adult the upper limit of HbA2 is typically about 3.5% of the total Hb. That’s why the best choice is the one stating “Under 3.5%.” In practice, the normal range is roughly 2.0–3.5%, so values above 3.5% can raise concern for conditions like beta-thalassemia trait, while values well below 3.5% are still within normal variation. The other options are not as close to the common reference range: 5% is higher than normal for most adults, 2% would be too low as an upper limit, and 10% is far outside the normal range.

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