The prevention and control of new coronavirus pneumonia is at a critical stage. As a diagnostic method, nucleic acid testing plays an important role in rapid diagnosis, efficacy evaluation, and epidemic prevention and control. It is currently the most important method of virus infection detection. The nucleic acid diagnostic kit has become a very important detection tool due to its many advantages. Here is a brief introduction to the relevant knowledge of the nucleic acid diagnostic kit.
Most of the current nucleic acid diagnostic kits use the fluorescent quantitative PCR method. The diagnostic principle is to use the unique gene sequence of the virus as the detection target. Through PCR amplification, the target DNA sequence we choose increases exponentially. Each amplified DNA sequence can be labeled with a fluorescence label that we added in advance. The probe binds to produce a fluorescent signal. The more target genes that are amplified, the stronger the accumulated fluorescent signal. In samples without virus, since there is no target gene amplification, no increase in fluorescence signal can be detected. Therefore, nucleic acid diagnostic is actually to determine whether there is viral nucleic acid in the sample by detecting the accumulation of fluorescent signals.
The development process of nucleic acid diagnostic kits is very fast, but the premise is that a certain amount of viral gene sequences must be mastered. Once the viral gene sequence is obtained, through bioinformatics analysis, candidate nucleic acid detection targets can be determined, and primers and probes can be designed. Among the components of the nucleic acid diagnostic kit, detection primers and probes are the most critical. Sensitive and specific amplification primers play a vital role in the accuracy of the detection results. Therefore, generally in the research and development stage, multiple pairs of primer probes are designed, and the primer probes with the best amplification effect are screened out through experiments and assembled in the viral nucleic acid diagnostic kit.
Every nucleic acid diagnostic kit must complete quality inspection and pass clinical sample assessment. The samples used for assessment have clear requirements on the quantity and type. Only by passing the clinical sample assessment of more than 3 independent medical institutions and the detection accuracy meets the clinical requirements, will it be possible to pass the approval of the State Food and Drug Administration and obtain the diagnostic reagent production batch number. At the same time, the accuracy of nucleic acid detection results is not only related to the detection accuracy of the kit itself, but also related to the timing of sample collection, the type of sample to be tested, and the type of sample to be tested. Different samples collected from the same patient at the same time may have very different test results.