POCT (point-of-care inspection) has developed rapidly in recent years, mainly due to the application of some new technologies. The development of POCT products has gone through the first generation of qualitative detection (test strip test paper); the second generation of semi-quantitative (swatch card colorimetry or semi-quantitative instrument reading); the third generation of full quantitative system (manual operation); the fourth generation of technology Platform (automation, informatization and intelligence).
The basic principles of POCT technology can be roughly divided into four categories:
(1) Immerse the relevant liquid reagents in the traditional method into the water-absorbing materials of filter paper and various microporous membranes to form an integrated dry reagent block, and then fix it on a rigid substrate to become various forms of diagnostic reagents strip.
(2) Miniaturize the traditional analytical instrument and simplify the operation method, making it a portable and palm-type device.
(3) Integrate the above two into a unified system.
(4) Apply bio-sensing technology and use bio-sensors to detect objects to be tested.
The specific technologies currently used can be summarized as follows:
1. Dry chemical technology
Dry chemical technology is to dry a variety of reaction reagents on a paper sheet, and use the liquid existing in the tested sample as a reaction medium, and the tested components directly react with the dry reagents solidified on the carrier. After adding the test specimen, a color reaction is produced, which is qualitatively or instrumentally detected by visual inspection (semi-quantitative). It is suitable for all kinds of samples such as whole blood, serum, plasma, urine, etc.
For example, the semi-quantitative detection of procalcitonin (PCT) uses this method. General chemical tests such as urine protein and glucose also belong to this category.
In recent years, dry chemical urinalysis has made great progress, and various types of urine sediment analyzers have come out one after another, providing a simple and fast screening method for clinical use, that is, to screen out completely normal specimens through a dry chemical urine analyzer. , which is conducive to the normative inspection of abnormal specimens.
After three expert seminars, the Chinese Medical Association formulated the screening criteria, that is, when all the dry chemical urine test strips are negative, microscopic examination of red blood cells and white blood cells can be omitted, and if there is a positive result, microscopic examination must be carried out at the same time.
In other words, so far no instrument can completely replace microscopy, and urine sediment microscopy is still an indispensable means of urinalysis with its unique clinical value.
2. Multilayer coating technology
The multi-layer coating technology is transplanted from the photosensitive film production technology. A variety of reaction reagents are sequentially coated on the film base to make dry films. The dry sheet made of multi-layer coating technology is smoother and more even than dry chemical paper sheet, and can be accurately quantified by instrument detection. For the monitoring of sugars, lipids, enzymes, electrolytes, non-protein nitrogen and some blood drug concentrations, dozens of items can be detected, almost covering the commonly used clinical biochemical test items. Because of its simple and fast operation, it is often used in emergency examinations, and some small instruments have also been introduced accordingly, which can be used for bedside examinations, but the cost of dry slices is relatively high.
3. Immunochromatography, Chromatography
POCT strip technology can be used to determine proteins and enzymes, such as myocardial markers, hormones and various proteins, etc., mostly qualitative tests. Separation of analytes in the matrix is accomplished by paper chromatography, and the analytes of interest are captured by specific antibodies immobilized on the surface of the chromatographic strip for qualitative analysis, which can be accomplished by color observation.
In addition, there are also small quantitative analyzers, such as the Cardiac Reader of Roche Company in Switzerland, which can be used to determine troponin T and myoglobin, as well as D-dimer. Males RG et al. found that biochemical markers are increasingly important in the diagnosis of acute myocardial infarction (AMI), especially when electrocardiography is not helpful. POCT technology can be used for in situ diagnostic analysis of the patient, and the biochemical markers most commonly used by doctors to help diagnose AMI are myoglobin (Mb), CK-MB, troponin I (cTnI) and troponin T (cTnT) ), which can be examined with POCT techniques and whose performance is comparable to laboratory-based myocardial markers.
Colloidal gold technology also belongs to the category of POCT. Colloidal gold, silver, selenium and pigments (including fluorescent and non-fluorescent pigments) can be firmly adsorbed on the surface of the antibody without affecting the activity of the antibody. When the labeled antibody reacts with the antigen and aggregates to a certain concentration , the color can be directly rendered. At present, the methods of gold, silver, selenium and pigment-labeled immune reactions mainly include spot diafiltration and immunochromatography, which are used to rapidly detect protein and polypeptide antigens, such as cTnT, serum albumin, hs-CRP and some viruses. Such as HBV, HCV, HIV, etc. antigen and antibody characterization. With the small detector, semi-quantitative and quantitative can be done.
At present, some companies have successively developed dozens of items in reproductive endocrinology, infectious diseases, venereal diseases, tumor markers, drugs, etc., using the principles of immunochromatography double antigen and double antibody sandwich method, combined with colloidal gold labeling technology, and nearly 100 specifications. Colloidal gold detection test product. Such as HCG test card, HBV test card and so on. Shiach CR et al. used POCT to measure prothrombin time (PT) in the laboratory and found that the two groups of INR times were similar, 60.19% and 59.13%, respectively, and the questionnaire showed that patients were very satisfied with POCT monitoring.
4. Selective Electrode Technology
Combining sensors including biosensors and chemical sensor technologies with ion-selective electrodes, a portable instrument for rapid detection of blood gas (PH, PCO2, PO2, etc.) and electrolytes (K+, Na+, Cl-, etc.) has been made, which has been widely used in clinical practice. .
5. Infrared and far-infrared spectrophotometric technology
It is often used to make percutaneous testing instruments, which can be used to detect blood hemoglobin, bilirubin, glucose and other components. This type of testing instrument can continuously monitor the target components in the patient's blood without blood drawing, which can avoid cross-infection and contamination of blood samples that may be caused by blood drawing, reduce the cost of each test and shorten the reporting time. However, the accuracy of the results of such percutaneous tests needs to be improved.
6. Biosensors
The new generation of POCT instruments uses biosensors. A biosensor couples a specific biodetector (such as an enzyme, antibody or nucleic acid probe) to a transducer for the direct measurement of the target analyte without separating it from the matrix. It embodies the combination of enzymatic chemistry, immunochemistry, electrochemistry and computer technology. It can be used for ultra-trace analysis of analytes in biological fluids, becoming the best framework for laboratory medicine. Such as the detection of electrolytes. Commercial POCT instruments use electrochemical techniques (eg, miniature ion-selective electrodes) and optical biosensors to measure glucose, electrolytes, and arterial blood gases. With the application of antibody immobilization technology and specific DNA sequences, biosensor probes will soon be used to detect hormones, drugs, difficult-to-cultivate bacteria, viruses such as chlamydia, tuberculosis, and human immunodeficiency virus.
7. Biochip
Biochip uses the concept of iniaturized Total Analysis System (uTAS) based on Micro Electro Mechanical System (MEMS) proposed at the end of the last century, and combines all sample processing and measurement steps into one. , analysts can obtain chemical information expressed in the form of electrical signals in a very short time and space interval. Microfluidic chip (Microfluidic Chip) is currently the most active field and development frontier in uTAS, which embodies the ideal of transferring analytical laboratory functions to chips, namely Lab-On-a-Chip (Lab-On-a-Chip, LOC), which is the crystallization of system integration microlithography technology, is a microchip that can complete the biochemical analyzer. Realize the miniaturization of the original inspection instrument and make it into a portable instrument for bedside inspection. Such as blood cell analysis, enzyme-linked immunosorbent assay (ELISA), blood gas and electrolyte analysis, etc. can be performed POCT.
At present, biochips can be divided into gene chip (Gene chip or DNA chip), protein chip (protein chip), cell chip (cell chip) and Lab-On-a-Chip (LOC), which have high sensitivity, It has the advantages of short analysis time and many simultaneous analysis items. It combines many analysis steps involved in life science research, using microelectronics, micromachines, physical technology, sensor technology, and computer technology to make the sample detection and analysis process continuous. , integration, miniaturization, and it can also promote the construction of microscale laboratories. The miniature laboratory has the characteristics of small size, easy portability, and can test a variety of biomolecules at the same time. It has great application value in the field of military medicine. With the development of science and technology, in the near future, the chip-based POCT instrument will gradually applied to various fields. For example, protein chips have been used in many fields, including the detection of biomarkers, the study of interactions between biomolecules and mass spectrometry, and the study of drug targets and their mechanisms of action.
