Final answer:
For a typical hematology test like a CBC, a lavender or purple top tube containing EDTA as an anticoagulant is used. This enables the proper separation and analysis of blood components upon centrifugation, critical for determining the hematocrit and overall cell counts.
Step-by-step explanation:
The correct tube for a typical hematology test, such as a complete blood count (CBC), is one that contains an anticoagulant. For a CBC, the tube commonly used is a lavender or purple top tube, which contains EDTA (ethylenediaminetetraacetic acid) as an anticoagulant. This prevents the blood from clotting and prepares it for the various measurements in the CBC, including the hematocrit, which measures the volume percentage of erythrocytes (RBCs) in the blood. When blood is centrifuged, the erythrocytes settle at the bottom, above which the buffy coat forms, consisting of leukocytes (WBCs) and thrombocytes (platelets). Plasma, the liquid component, makes up the top layer of the centrifuged sample. The hematocrit is especially important in assessing conditions such as anemia or polycythemia.
Heparin is another anticoagulant that can be used in blood collection tubes, like those containing lithium heparin, but these are generally used to obtain plasma for chemistry tests rather than for a hematocrit measure. Blood type testing, separate from a CBC, involves using anti-A and anti-B antibodies to determine the presence of specific antigens on the surface of erythrocytes. The process of crossmatching, critical in transfusions, ensures compatibility to prevent adverse reactions.