HEMATOLOGY ANALYZERS

Hematology analyzer is a computerized, highly specialized machine to count the number of red and white blood cells, blood platelets, hemoglobin, and hematocrit levels in a blood sample. There are hematology analyzers that are for human blood or animal blood, which is useful for veterinarians, zoos, and research labs. Features vary from one hematology analyzer to another, such as closed vial testing and open sampling testing. Certain hematology analyzers allow the user to choose the preferred testing type. Other features to consider in a hematology analyzer are the sample size required, type and quantity of testing modes, speed in which the results are available, automatic flagging of results that are out of normal range, and the capacity of test results it can store.Basic analyzers return a complete blood count (CBC) with a three-part differential white blood cell (WBC) count. Sophisticated analyzers measure cell morphology and can detect small cell populations to diagnose rare blood conditions.

The three main physical technologies used in hematology analyzers are:

• Electrical impedance,
• Flow cytometry
• Fluorescent flow cytometry

These are used in combination with chemical reagents that lyse or alter blood cells to extend the measurable parameters. For example, electrical impedance can differentiate red blood cells (RBC), WBCs, and platelets by volume. Adding a nucleating agent that shrinks lymphocytes more than other WBCs makes it possible to differentiate lymphocytes by volume. A single-cell stream passes through a laser beam. The absorbance is measured, and the scattered light is measured at multiple angles to determine the cell’s granularity, diameter, and inner complexity These are the same cell morphology characteristics that can be determined manually from a slide.

Electrical impedance

The traditional method for counting cells is electrical impedance, also known as the Coulter Principle. It is used in almost every hematology analyzer.

Whole blood is passed between two electrodes. through an aperture so narrow that only one cell cant pass through at a time. The impedance changes as a cell passes through. The change in impedance is proportional to cell volume, resulting in a cell count. and measure of volume.

Flow cytometry

Flow cytometry is a laboratory method used to detect, identify, and count specific cells. This method may be used to evaluate cells from blood, bone marrow, body fluids such as cerebrospinal fluid (CSF). or tumors. Laser flow cytometry is more expensive. than impedance analysis, due to the requirement for expensive reagents, but returns detailed information about the morphology of blood cells. It is an excellent method for determining five-part WBC differentials.

Fluorescent flow cytometry

Adding fluorescent reagents extends the use of flow cytometry to measure specific cell populations. Fluorescent dyes reveal the nucleus-plasma ratio of each stained cell. It is useful for the analysis of platelets, nucleated RBCs, and reticulocytes.