Where should one read the percentage of packed red blood cell column from a microhematocrit reading device?

In a microhematocrit reading, the percentage of packed red blood cells (RBCs) is determined by measuring the height of the red blood cell layer in relation to the total height of the blood column after centrifugation. The correct approach is to read the percentage at the top of the red blood cell layer, as this accurately reflects the packed cell volume.

When using a microhematocrit tube, after centrifugation, the components separate into three distinct layers: plasma at the top, a thin layer of white blood cells and platelets (the buffy coat) in the middle, and then the red blood cells at the bottom. The height of the packed red blood cells is crucial for determining the hematocrit value. This is typically indicated just above the boundary line where the red blood cells meet the buffy coat, providing a clear separation to ensure accurate measurement.

Reading from the correct point not only yields a precise hematocrit value but also helps when comparing results across different samples or testing conditions. Thus, measuring at the top of the red blood cell layer is essential for obtaining accurate and reliable hematocrit values in clinical settings.