Automation in Hematology | Term Paper | Laboratory | Hematology

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Term Paper on Automation in Hematology

The automation is mechanization of various duties performed by machines or analyzers which helps to lessen the work load in laboratories.

The various duties are performed which are as follows:

1. Collecting, labelling, separating and preserving various specimens (such as blood, plasma, scrum, etc.)

2. Pipetting reagents.

3. Mixing reagent and specimen.

4. Incubating reaction mixtures at specific temperatures.

5. Calculating test results.

6. Printing Test reports.

Introduction of automation in the routine test performed in hematology has considerably improved the accuracy of results and also the efficiency of the laboratory.

There are two major technique currently used for automated cell counting:

1. Electrical impedance cell counting.

2. Light scatter cell counting

Advantages of an Auto Analyzer:

The following are the various advantages if auto analyzers are:

1. Large number of samples can be tested in a short time.

2. Variety of tests can be performed by using various methods such as end point and rate of reaction.

3. By using techniques such as ELISA etc. it is possible to determine concentration of hormones, drugs and various antibodies.

4. Most of methods performed in automation are accurate, precise and specific.

Electrical Impedance Cell Counting:

This electrometric method of cell counting, first devised by the coulter counter is still the most popular one.

Blood cells are suspended in an electrolyte solution (Isotone) and made to flow from an outer chamber into an inner chamber through an orifice of 100 (am diameter. An electrode is placed in each chamber to sense the electric current flowing through the orifice. When a cell (Poor conductor of electricity) passes through the orifice, it imparts resistance to the electrical.

Conductivity between the two chambers the resistance shown when each cell flows through the orifice is recorded as a voltage pulse that corresponds to counting of cell. The degree of resistance, which is proportional to the volume of cell, gives the machine the capability of measuring the size of the cell.

Red cells and white cells are counted separately by diluting the blood in different diluents. The white cell diluents is Drabkin solution, which in addition to the WBC count, reports Hb concentration.

Measurement of Red Cell Indices:

Measurement of red cell indices of all the indices, MCV is actually measured from the average amplitude of voltage pulse in the region of red cell size (6-9µm)

Hematocrit value is calculated from MCV and RBC count (MCV X RBC in Millions divided by 10).

Diluents for Red Blood Cell Counting:

Always use the diluents suggested by the manufacture as it increases the work capacity of machine. Eagle’s solution can be used in place of Isoton. Phosphate-Buffered Physiological saline (0.85% NaCL), adjusted to pH 7.4 is acceptable.

Use a combination of kh₂po4 and Na₂HPo4 (0.1 % solution of each) and adjust the pH before the final volume of NaCl solution is made. The diluents must be particle free, hence use distilled water and good quality reagents, filter it necessary through millipore filters.

Light Scatter Cell Counting:

In this method, a laser or a tungsten halogen lamp is pointed towards the blood stream, which passes through a channel that is a so narrow that cells can only pass through one by one. This is achieved through a hydro-dynamically focussed flow, called sheath flow.

When the cell passes through the light beam the light is scattered or reflected into a particular direction, which depends mainly on the size of the cell but also in the shape and the refractive index.

A photo detector is placed at the angle at which the light is scattered. The use of lasers is preferred due to the focussed light beam they produce. Calibration of these instruments has to be performed using human blood.

Automated Differential Count:

In order to achieve differential counts, it is necessary that the instrument can distinguish the different cell types. This can be done in both two techniques of cell counting.

The basic principles that are used are:

i. For the electrical impedance based instruments such as the Beckman coulter series, the cells are subjected to special reagent which shrinks the cytoplasm of each type white blood cell (WBC) to a different degree. This allows classifying the cell by size.

ii. Instruments like the Hemalog Diluted stain from technicon corp. use chemicals that influences or stain the cells in specific ways and the cell can thus be distinguished when illuminated by a laser beam either by their scattering properties or the colour of the light that they emit.

iii. The light scattered method can be refined such that the intensity of the scattered light is measured in various angles.

iv. With the availability of digital camera and computing power, the computer can also emitate the manual methods.