Measurement Techniques for Counting White Blood Cells and Red Blood Cells: From Manual Methods to Modern Automated Analyzers

Introduction

The measurement of white blood cells (WBCs) and red blood cells (RBCs) in blood is a crucial component of a complete blood count (CBC) test, which provides valuable insights into a person's overall health and can indicate various medical conditions such as anemia, infections, and more.

Modern Automated Hematology Analyzers

Today, the most common method for counting WBCs and RBCs is through the use of automated hematology analyzers. These advanced devices employ sophisticated techniques such as electrical impedance, laser light scattering, and fluorescent dyes to rapidly and accurately count and classify blood cells.

Automated Cell Counters:

Electrical Impedance: These devices use an electrical current to detect the presence of cells based on their size and shape. As the cells pass through the detection field, the electrical resistance changes, allowing the analyzer to count and classify the cells.

Laser Light Scattering: This technique measures the light scattered by cells, providing information about cell size, shape, and complexity. The detector records the intensity and angle of scattered light to characterize the cells.

Fluorescent Dyes: Some analyzers use fluorescent dyes that bind to specific cell components, allowing for precise identification and counting of particular cell types.

The automated process is both time-efficient and highly accurate, making it the preferred method in most clinical settings for routine health checks and the diagnosis of various medical conditions.

Manual Blood Count Methods Before Modern Analyzers

Before the advent of modern electronic analyzers, manual methods were employed to count WBCs and RBCs. These techniques, while less precise and more labor-intensive, provided a foundation for modern practices and garnered important insights into blood cell behavior.

Sample Collection: A healthcare professional would draw a small sample of blood from a vein in the arm using a sterile needle and collection tube.

Laboratory Analysis:

Preparation of Blood Smears:

Samples were prepared by diluting the blood with normal saline.

Dyes were added to the white blood cells to enhance their visibility under a microscope.

The blood was then smeared onto specialized glass slides, which were then dried and stained with specific dyes.

Manual Counting:

Etched glass square chambers were used to count cells. These chambers had different sizes to accommodate various cell types.

A hand clicker was used to count the cells within a specified area of the chamber.

The cells were counted in multiple chambers, and the results were multiplied by the dilution factor to obtain an accurate count.

Results Interpretation: The manual counts provided valuable information about the patient's overall health and helped diagnose various medical conditions, including anemia and infections.

User-Friendly Automated Counters: The Coulter Counter

The Coulter Corporation introduced the Coulter Counter in the late 1960s, marking a significant advancement in blood cell counting technology.

Counting Mechanism:

Cell Dyeing and Dilution:

Cells were dyed with specific stains to increase their optical differences.

The sample was then diluted to create a very thin suspension of cells.

Flow-Through Technology:

The diluted sample was passed through a narrow aperture.

An electric charge was applied across the aperture, and each cell that passed through the charge field created an interruption.

The size of the interruption was used to calculate the cell's size and shape.

Automated Results:

The machine would automatically print out the results, providing a quick and accurate count of WBCs and RBCs.

The Coulter Counter was a groundbreaking innovation that transitioned blood cell counting from a highly labor-intensive and time-consuming process to a fast, efficient, and highly accurate one.