Which artifact is associated with under-filled EDTA tubes in hematology testing?

Which artifact is associated with under-filled EDTA tubes in hematology testing?

• A. Falsely decreased microhematocrit
• B. Falsely elevated hemoglobin
• C. ESR value not affected
• D. Falsely decreased RBC count

Answer: (A)

The main idea is that filling accuracy matters for measurements that rely on the actual blood volume in a tube. For microhematocrit, you measure the proportion of red blood cells by comparing the height of the red cell column to the total column after centrifugation. If the EDTA tube is under-filled, there is an air space and less blood in the capillary. After centrifugation, the red cell layer ends up shorter than it would with a properly filled sample, so the hematocrit value appears lower than the true value. The anticoagulant itself isn’t causing this error—the issue is the insufficient blood volume and the resulting air space in the column.

The main idea is that filling accuracy matters for measurements that rely on the actual blood volume in a tube. For microhematocrit, you measure the proportion of red blood cells by comparing the height of the red cell column to the total column after centrifugation. If the EDTA tube is under-filled, there is an air space and less blood in the capillary. After centrifugation, the red cell layer ends up shorter than it would with a properly filled sample, so the hematocrit value appears lower than the true value. The anticoagulant itself isn’t causing this error—the issue is the insufficient blood volume and the resulting air space in the column.