Which instrument is used as the standard method for keeping track of cell counts in a sample?

Which instrument is used as the standard method for keeping track of cell counts in a sample?

• A. Standard WBC counting device
• B. Hemocytometer
• C. Hematocrit tubes
• D. PCV card reader

Answer: (A)

Using a hemocytometer is the standard approach because it provides a direct count of cells in a precisely defined volume. You dilute the sample, load a small, known volume into the counting chamber, and count cells in specific grid squares under a microscope. Since the chamber depth and the grid area are fixed, those counts can be converted into cells per microliter by applying the dilution factor. This method has long served as the reference for manual counts of WBCs, RBCs, and platelets and is used to validate automated counters. Hematocrit tubes measure the proportion of red blood cells in blood after centrifugation, giving hematocrit (or PCV) rather than the actual cell concentration per volume. A PCV card reader reads that hematocrit value, not the cell count. A generic “standard WBC counting device” isn’t a specific, recognized instrument for counting cells; counting is done with a hemocytometer or an automated hematology analyzer.

Using a hemocytometer is the standard approach because it provides a direct count of cells in a precisely defined volume. You dilute the sample, load a small, known volume into the counting chamber, and count cells in specific grid squares under a microscope. Since the chamber depth and the grid area are fixed, those counts can be converted into cells per microliter by applying the dilution factor. This method has long served as the reference for manual counts of WBCs, RBCs, and platelets and is used to validate automated counters.

Hematocrit tubes measure the proportion of red blood cells in blood after centrifugation, giving hematocrit (or PCV) rather than the actual cell concentration per volume. A PCV card reader reads that hematocrit value, not the cell count. A generic “standard WBC counting device” isn’t a specific, recognized instrument for counting cells; counting is done with a hemocytometer or an automated hematology analyzer.