Final answer:
Hematocrit is the test used to measure packed RBCs in a blood sample.
Explanation:
Hematocrit is the test that measures the amount of packed RBCs in a blood sample. It determines the percentage of red blood cells (erythrocytes) compared to other components of blood by spinning the blood in a centrifuge, which separates the heavier elements like RBCs at the bottom. This test is also known as packed cell volume (PCV), with normal values around 45% in a blood sample.
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