What is the Rule of 3 relationship between Hgb, Hct, and MCHC?

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Multiple Choice

What is the Rule of 3 relationship between Hgb, Hct, and MCHC?

The Rule of 3 in a CBC is a quick check that ties together hemoglobin, hematocrit, and MCHC. In adults, the hematocrit is roughly three times the hemoglobin concentration, so Hct ≈ Hgb × 3. Allowing for small measurement variation, this is often written as Hgb × 3 ≈ Hct ± 3. The MCHC (mean corpuscular hemoglobin concentration) reflects how concentrated hemoglobin is inside red cells and normally stays within a narrow range around 32–36 g/dL, which is 320–360 g/L depending on units. So the best choice matches both parts: Hgb × 3 ≈ Hct ± 3 and MCHC is about 320–360. The other options misstate the Hgb–Hct relationship (using a different multiplier or tolerance) or give an incorrect MCHC range that doesn’t align with the typical normal values.

The Rule of 3 in a CBC is a quick check that ties together hemoglobin, hematocrit, and MCHC. In adults, the hematocrit is roughly three times the hemoglobin concentration, so Hct ≈ Hgb × 3. Allowing for small measurement variation, this is often written as Hgb × 3 ≈ Hct ± 3. The MCHC (mean corpuscular hemoglobin concentration) reflects how concentrated hemoglobin is inside red cells and normally stays within a narrow range around 32–36 g/dL, which is 320–360 g/L depending on units.

So the best choice matches both parts: Hgb × 3 ≈ Hct ± 3 and MCHC is about 320–360. The other options misstate the Hgb–Hct relationship (using a different multiplier or tolerance) or give an incorrect MCHC range that doesn’t align with the typical normal values.

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