Development history of blood analyzers

Routine blood examination refers to the analysis of the quality and quantity of various parameters of the blood system such as red blood cells, white blood cells, hemoglobin and platelets in the blood through the detection of trace amounts of blood.

A routine blood test report includes red blood cells (RBC), hemoglobin (Hb), white blood cells (WBC), white blood cell differential count and platelets (PLT).

The blood routine report has a lot of content, which can be divided into three major parts, namely the red blood cell system, the white blood cell system and the platelet system.

Under a light microscope, leukocytes can be divided into two types: agranulocytes and agranulocytes according to whether they have special granules in their cytoplasm.

Granulocytes are further divided into neutrophils, eosinophils and basophils based on the chromophilic nature of the granules. There are two types of agranulocytes: monocytes and lymphocytes.

So, since blood cells are so small, how can we know the number of various blood cells in a drop of blood? How are the various blood routine data on our physical examination report sheet calculated?

The invention of the "automatic blood cell counter" is indispensable.

automatic blood cell counter
In the 13th century AD, Arab medicine began to realize the small circulation of blood. In 1628 AD, Harvey of England proved the theory of blood circulation.

The systematic and scientific study of blood began after the advent of the microscope. Using a microscope to observe red blood cells, white blood cells and platelets in the blood, called the tangible part of the blood, is the focus of hematologists' research.

The detection of blood cell numbers relies on the successive invention of blood cell pipettes, blood cell counting boards, hemoglobin meters and cell sorting technology.

The earliest counting was done with the naked eye using a counting board (the most commonly used is a bovine Bowen counting board), and using 1% hydrochloric acid to destroy the red blood cells and then count the white blood cells. Then use a Salieto colorimeter to calculate hemoglobin. Hemoglobin multiplied by 3.3 is approximately the number of red blood cells.

The world's first automatic blood cell counter was born in 1953.

In 1946, in a basement laboratory in Chicago, Wallace H. Coulter and his brother Joseph R. Coulter began their research.

The original method was to flow a suspension containing cells through a capillary tube under a microscope and use a beam to count people like people marching in a parade, but did not achieve a good pulse sensing signal.

Blood cells are insulators, they thought of electric current.

The two poles of the power supply are separated by cellophane. When cells suspended in the solution flow through the small hole, the blood cells change the resistance in the small hole circuit, and a voltage pulse signal appears.

In this way, cells can be accurately counted by counting the number of pulses.

The amount of liquid displaced by the cell in this small hole (equal to its own volume) is proportional to the voltage pulse. Moreover, the signal strength is about 10 times that of the photoelectric method!

In 1949, they submitted a patent application. But several lawyers, including patent examiners, doubted whether a "tiny hole" could be patented.

However, Kurt and the others provided some similar application examples of small holes in other fields. In the defense statement, they described particle sensing in narrow current channels and also described situations with non-circular holes.

On October 20, 1953, the U.S. Patent Office granted its invention patent.

This is the classic Coulter principle.

If you don’t understand, in layman’s terms, it’s like a funnel. When you put beans of different colors in the funnel, let it slowly leak out. When you see white beans, you know they are white beans. When you see red beans, you know they are white beans. You know it is a red bean, and you count each bean you pass by, so that you know the number of each bean.

This funnel actually acts as a hemocytometer.

Changes in routine blood testing instruments
A blood cell analyzer essentially refers to an instrument that analyzes the number and heterogeneity of blood cells within a certain volume.

The original blood cell counter (Cell Counter) could only count red blood cells (RED) and white blood cells (WBC). Later, hemoglobin (HBG), platelets (PLT), hematocrit (HCT), mean corpuscular volume (MCV), etc. several parameters.

After developing into a hematology analyzer (Hematology Analyzer), many analysis and calculation parameters were added:

Such as red blood cell volume distribution width (RDW), mean platelet volume (MPV), platelet volume distribution width (PDW), platelet packed volume (PCT), large platelet ratio, three white blood cell groups, five white blood cell groups, hemoglobin concentration distribution width, abnormal lymphocytes Various parameters and functions such as cell prompts and naive cell prompts are also continuously added to some brands of instruments.

In 1974, a white blood cell analyzer called HEMALOG D with preliminary white blood cell classification function came out.

In 1982, Technicon produced the H6000 blood cell analysis instrument, which should be the first instrument with five-differentiation capabilities for white blood cells.

Around 1990, many manufacturers in Europe and Japan successively launched various types of blood cell analysis instruments with five-differentiation functions for white blood cells.

Such blood cell analyzers designed and produced by various manufacturers have different principles in white blood cell classification technology, slightly different analysis and measurement items, various forms, and complex structures.

Three categories and five categories refer to the white blood cell groups in blood routine.

The three classifications divide white blood cells into large cells (neutrophils), intermediate cells (other white blood cells), and small cells (lymphocytes), that is, small, medium, and large cell groups;

The five-category classification is more accurate and divides white blood cells into lymphoid group, mononuclear group, neutral group, eosinophilic group and basophilic group.

Many machines can produce many derivative projects, such as other various subgroups, etc. The more detailed the classification items are and the more derived items they are, the more meaningful they are for clinical guidance.