The optical coagulation meter measures coagulation function based on the changes in turbidity during plasma coagulation. According to the different optical measurement principles of the instrument, it can be divided into two categories: scattering turbidimetry and transmission turbidimetry.
Scattering turbidimetry determines the detection endpoint based on the changes in scattered light of the sample to be tested during the coagulation process. In this method, the monochromatic light source of the detection channel is at a right angle of 90° to the light detector. When a coagulation activator is added to the sample, the scattered light intensity of the sample gradually increases with the formation of fibrin clots in the sample. When the sample is completely solidified, the intensity of scattered light no longer changes. Usually, the starting point of solidification is regarded as 0%, the end point of solidification is regarded as 100%, and 50% is regarded as the solidification time. The light detector receives this optical change, converts it into an electrical signal, amplifies it and then transmits it to the monitor for processing to draw the coagulation curve.
Transmission turbidimetry determines the end point of coagulation based on the absorbance change of the sample to be tested during the coagulation process. Different from scattering turbidimetry, the light path of this method is the same as a straight line like the general colorimetry method. Arrangement: The light from the light source is processed and turned into parallel light. After passing through the sample to be measured, it shines on the photoelectric tube and turns into an electrical signal. After amplification, it is monitored and processed. When the coagulation activator is added to the sample, the initial absorbance is very weak. As the fibrin clot forms in the reaction tube, the absorbance of the sample gradually increases. When the clot is completely formed, the absorbance tends to be constant. The coagulometer can automatically draw the absorbance change curve and set the time corresponding to a certain point as the coagulation time. The magnetic bead method measures coagulation function based on changes in viscosity during plasma coagulation. According to the different measurement principles of the magnetic bead movement of the instrument, it can be divided into photoelectric detection method and electromagnetic bead detection method.
Photoelectric detection method. The role of the photodetector in the magnetic bead method is different from that in the optical method. It only measures the movement pattern of the magnetic beads during the plasma coagulation process and has nothing to do with the turbidity of the plasma. In the magnetic bead method, a pair of electromagnets are placed at both ends of the test cup. They generate a constant alternating magnetic field to make the magnetic beads swing in the test cup. A pair of photoelectric receiving devices are placed in the perpendicular direction to the swing of the magnetic beads. When the magnetic beads swing, The end point of solidification is determined when the bead swing amplitude decays to 50%.
There is another photoelectric detection method that uses an infrared light reflection monitor to monitor the movement of magnetic beads. This will be introduced in the following introduction to the BE series semi-automatic coagulation analyzer.
The electromagnetic detection method can also be called the dual magnetic circuit magnetic bead method. One pair of magnetic circuits is used to attract the magnetic beads to swing, and the other pair of magnetic circuits uses the cutting of magnetic lines of force generated by the magnetic beads during the swing process. The electrical signal is used to monitor the magnetic bead swing amplitude reading. When the magnetic bead swing amplitude attenuates to 50%, the coagulation end point is determined. Currently commercially available semi-automatic hemagglutination meters mainly consist of samples, reagent pre-warming tanks, sample injectors, detection systems (optics, magnetic field) and microcomputers. Some semi-automatic instruments are also equipped with a chromogenic detection channel, so that such instruments have the function of detecting the activity of anticoagulant and fibrinolytic systems at the same time. In view of the shortcomings of the optical semi-automatic coagulation meter, which are affected by human factors and have poor repeatability, there should be an automatic timing device in the instrument to inform the pre-warming time and the optimal reagent addition time; a reagent sensor is added to the test position. The latter automatically vibrates after sensing the reagent dropped from the pipette needle, so that the plasma and reagents can be well mixed during the reaction; in addition, this type of instrument is equipped with a pipette guide plate on the top of the test cup, which is guided by the guide plate when adding reagents. To fix the pipette needle, it ensures that reagents can be added at a fixed and optimal angle every time and prevents the generation of bubbles. This series of improvements has improved the accuracy of optical semi-automatic coagulometer detection.
Generally, semi-automatic coagulation meters can be used for coagulation tests, while coagulation tests that require other testing methods can be performed with biochemical analyzers, microplate readers, etc. The basic components of this type of instrument include: sample transfer and processing device, reagent refrigeration position, sample and reagent distribution system, detection system, electronic computer, output equipment and accessories, etc.
1. Sample transmission and processing device: Generally, plasma samples are moved from the transmission device to the position of the sample suction needle. Most instruments are also equipped with emergency positions, which can suspend routine specimen testing when necessary to comply with the immune ratio. In the turbidimetric method, the test substance is mixed with its corresponding antibody to form a complex, resulting in large enough precipitated particles, which are measured by transmittance or scattering turbidimetry. This method is simple to operate, has good accuracy and is easy to automate.
2. Reagent refrigeration position: In order to avoid the deterioration of reagents, the instrument often has a reagent refrigeration function. Generally, dozens of reagents can be placed for refrigeration at the same time.
3. Sample and reagent distribution system: The sample arm will automatically lift the test cup in the specimen tray and place it in the sample pre-warming tank for pre-warming. Then the reagent arm injects the reagent into the test cup (the fully automatic coagulometer with superior performance has an independent thrombin suction needle to avoid contamination of other detection reagents by thrombin), and a device with a vortex mixer mixes the reagent with the sample. After thorough mixing, it will be sent to the testing position, and the tested test cup will be automatically discarded in a special waste bin by the device.
4. Detection system: This is the key part involving the measurement principle of the instrument. The coagulation of plasma can be detected by the coagulation reaction detection method, that is, when the fibrin clot is formed, the change in the absorbance of the turbid liquid at 660nm of scattered light is detected; or by the coagulation point detection method, that is, by calculating the preset absorbance value. The coagulation time of the magnetic bead method is to determine the plasma coagulation point by measuring the change in the swing amplitude of a small steel ball under a certain magnetic field strength. The chromogenic substrate method and immunological method detect the absorbance changes of the reaction solution at 405nm, 575nm and 800nm ??to reflect the activity of the substance being detected.
5. Electronic computer: According to the set program, the computer directs the coagulation instrument to work and analyzes and processes the detected data, and finally obtains the test results. The computer can also store the patient's test results, remember various errors during the operation, and perform quality-related work.
6. Output device: Output the test results through the computer screen or printer.
7. Accessories: Mainly include system accessories, capping system, barcode scanner, positive sample analysis scanner, etc.