Choosing the Right Hematology Analyzer

Horiba impedance hematology analyzer

It is important to know the counting technology used by the device because it may cause results to vary. For hematology analyzers, we usually distinguish between:

• Flow cytometry: this is the most sophisticated and expensive method available today. It consists of moving the cells in a narrow flow before a laser beam. The laser beam hits them one by one and a light detector captures the light reflected from the cells. This is called laser flow cytometry. There is also fluorescence flow cytometry, which works on the same principle as laser flow cytometry except that the type of detection differs.
  In general, flow cytometry allows for much more than just counting, such as analyzing the shape of cells and their internal and external structure. As a result, this technique is rarely used for the sole purpose of counting cells.
• Electrical impedance: this technique is used to determine the number and volume of erythrocytes and thrombocytes. For this purpose, EDTA blood is diluted with an isotonic solution inside the device and aspirated through a capillary opening. The cells then move one by one through an electric voltage field where they induce a pulse (increase in electrical resistance) according to their size. This makes it possible to differentiate between large cells and small ones and thus to count them.
• Laser scattering: this technique measures the size distributions of particles. In order to do this, it measures the angular variation in the intensity of scattered light when a laser beam passes through a sample of scattered particles. Large particles scatter light at small angles in relation to the laser beam, while small particles scatter light at larger angles. This means we can calculate the size of the particles from the diffraction pattern they create.

In addition to the measurement technology, it is important to consider several other points:

• The number of parameters that the device can provide. This refers to all of the types of data the device can provide concerning the measured elements. For example, the number, volume and concentration of each element. Depending on the equipment, hematology analyzers can range from prodviding nine to over 50 parameters.
• White blood cell differentiation. Leukocytes can be divided into three types: lymphocytes, monocytes and granulocytes. Granulocytes can also be differentiated into three groups: basophilic granulocytes, eosinophilic granulocytes and neutrophilic granulocytes. There is therefore a total differentiation into five types. Some analyzers do not offer leukocyte differentiation.

The major brands in the sector offer fully integrated systems however. These are intended to be part of a high-capacity diagnostic platform and can be linked to other analytical modules (biochemistry, immunology, etc.)

When choosing reagents, it is very important to pay close attention to the brands, depending on whether the analyzer is in a closed system or not. Closed systems only accept reagents of the same brand as the device. Analyzers compatible with any reagent brand are called “open.”

There are many types of reagents depending on the specific applications (diagnostic and clinical) of the device. To ensure the proper functioning of the analyzer, you will need to have calibrators, control solutions, diluents and dyes.

There are several different advantages:

• Speed because the analysis process is generally automated, this reduces or even eliminates the need for manual intervention. This also has the positive impact of increasing the level of accuracy and limiting the number of errors. Human errors are one of the main problems with manual counting.
• Accurate results with better cell differentiation.
• Versatility with a diversity of measured parameters.

The disadvantages can be as follows:

• Cost as the acquisition of a hematology analyzer requires a significant investment. You will also have to take into account the cost of reagents.
• Maintenance as the equipment requires regular monitoring and quality control to ensure that the device is functioning properly. Depending on the laboratory’s resources, this can be a limiting factor.
• Size as depending on the product range and characteristics, some analyzers can be very cumbersome.

In addition to the ability to differentiate leukocytes (see question 2), a hematology analyzer can include different options such as:

• An auto-sampler to manage the samples.
• A system for staining and preparing slides in case a test result requires a smear.
• CRP (C-reactive protein) analysis to see if there is a risk of inflammation.
• A touch screen for a better user experience.