Which of the following laboratory tests can be taken using an EDTA vacutainer tube?

The use of an EDTA vacutainer tube is specifically suited for tests that require the preservation of cellular components and whole blood analysis. Among the options provided, the Erythrocyte Sedimentation Rate (ESR) test is commonly performed in EDTA tubes because it measures the rate at which red blood cells settle in a period of one hour. This test relies on the intact red blood cells and their behavior in plasma over time, making the anticoagulation properties of EDTA essential for maintaining sample integrity.

In contrast, while INR (International Normalized Ratio) is a test used to assess blood coagulation, it is typically performed on citrate tubes to prevent coagulation rather than on EDTA tubes. Electrolytes are generally measured in serum or heparinized plasma samples, not in EDTA tubes. Finally, although fibrinogen can be tested using various sample types, it is most commonly done using serum or citrated plasma rather than using EDTA, where the presence of anticoagulants can interfere with the measurement.

Thus, the choice of the ESR test aligns with the unique properties of EDTA, making it the appropriate test for a sample collected in an EDTA vacutainer.