Epidemic prevention science | a nucleic acid testing report is born…

2022-08-04 0 By

For citizens, nucleic acid testing may seem like a two-step process: register, sample, and wait for the results.In fact, behind these seemingly easy two steps, there is a lot of work by the inspectors in the GENE amplification laboratory (PCR laboratory).The birth of a nucleic acid report must go through sampling, specimen transport, specimen receipt, nucleic acid extraction, nucleic acid transfer, nucleic acid amplification, results review……Sweat oozed from his forehead and hot breath blurred his goggles as an examiner in a thick protective suit meticulously examined nucleic acid samples at a laboratory table.Many people think that nucleic acid samples, directly with the machine test results can be quickly.In fact, after the sampling nurse “gently twirls slowly” in the pharynx, the follow-up also includes sample receipt, nucleic acid extraction, nucleic acid transfer, nucleic acid amplification, results review and other steps.After nucleic acid test samples are collected, the collection personnel will count the number, pack them in sealed bags, spray them with disinfectant, and then put them into the sample transfer box, and send them to the nucleic acid test laboratory by special personnel.After receiving the samples, the inspectors will disinfect the container first, and disinfect the inner wall of the container and the sealed bag of specimen collection for a second time after opening it, before opening the sealed bag and taking out the samples.There is barcode information on the nucleic acid collection tube, and the receiver should clarify which community or population the sample comes from, and whether it is single collection or mixed collection.Also, pay attention to the time on the sample so that you can go back if you need to.After that, the nucleic acid sample will go through the second step of the “life of life” – the “ID card”.Inspectors refer to this step as “sample pre-processing.”PCR was performed on a 96-well plate, with each well site having its own unique identity.It may seem like “pre-processing” for inspectors to number and input information into the samples just delivered, but they should not let their guard down at all.The inspector should identify the occurrence of atC or spillage.Especially in the case of 10:1 mixed sampling in a large population, small test tubes are crowded with swabs. Once positive samples are spilled, on the one hand, other sample results may be contaminated (false positive).On the other hand on laboratory biological safety threat, it is also the PCR laboratory inspection personnel also dressed as the cause of the “white” appearance – medical hat, N95 mask, face screen, goggles, medical protective clothing, protective clothing, disposable shoe covers, two layers of gloves, these “bound” can give inspection personnel to create the safest environment.In addition, PCR laboratories require strict zoning, preferably a negative pressure laboratory.Air flows only from the outside in, so the pollution in the laboratory will not spread to the outside, which can ensure the safety of the outside of the laboratory.Nucleic acid samples that “pass by” the virus or are only 2 millimeters short of an ID card cannot be tested directly, but nucleic acid must be extracted and amplified.So the next stage of the nucleic acid adventure is the PCR addition zone, where the examiner pinpoints the genetic material (RNA) of the virus.At this point, the inspector wearing double gloves unscrewed the screw cover one by one in the biosafety cabinet, manually absorbed the sample, added the nucleic acid extraction plate hole, and then screwed the screw cover to put the specimen back to its original place.The coronavirus “brush” may come within two layers of latex gloves — that is, 2mm — but nucleic acid testing does not allow for fear.After obtaining the nucleic acid, the inspector transfers the nucleic acid with a pipette gun to the reaction tube prepared with the reaction liquid in advance to make the reaction system and let it enter the next stop of “Fantasy” : the amplification analysis area.No mistakes, no omissions, no biosafety incidents.It can be said that inspectors are always in a state of high tension.To take “sample” alone, inspectors must use tiny spear tips to add each extracted nucleic acid, about a quarter of a drop of water, to the reagent, and every step must be taken with great care.Although there are instruments to open and add samples, the speed of the existing instruments is not satisfactory, and the screening of large samples can only rely on manual operation.After a complicated and time-consuming preparation process, the sample finally arrives at the crucial stop in Life.The quality of the sample, the quality of the nucleic acid extraction, and the results will be determined here.Here have to mention who won the Nobel Prize of polymerase chain reaction (PCR), which is developed in the mid – 1980 – a in vitro nucleic acid amplification techniques, it can target gene fragment amplified one million times within a few hours to hundreds of millions of times, become the modern life science research one of the most important and widely used technology.How do you understand amplification?If the nucleic acid extracted from a sample is regarded as a piece of land, and the novel coronavirus is the seed, how do we know if there are seeds in the soil?The simple way is to add water and fertilizer (reagent) to make one seed become two, two become four, four become eight…You can’t see the virus, and it’s not easy to detect a tiny sample, so you have to make it big enough to detect it.When the reaction tube is tested on the machine, it means that “there is no turning back” — any problems in the process from sampling to nucleic acid preparation can lead to retesting, doubling the reporting time.On March 15, the National Health Commission released COVID-19 Diagnosis and Treatment Protocol (Trial Version 9).Among them, the Protocol has modified the criteria for release of isolation management and discharge to “Ct values of BOTH N gene and ORF gene in two consecutive Novel Coronavirus nucleic acid tests are ≥35 (fluorescence quantitative PCR method, cut-off value is 40, sampling time interval is at least 24 hours)”, which also lets many “white people know that the” Ct “here is not to go to the hospital for Ct examination.It refers to the threshold of amplification.In simple terms, the lower the Ct value, the stronger the positivity;The higher the Ct value, the weaker the positivity.As a primary screening laboratory, it can only report “suspected positive” to CDC and then transfer primary specimens for review as required by CDC.PCR LABS are also sterilized by ultraviolet light, and negative samples are usually stored for a day or two for testing.Behind the report rushing to you is sweat detection personnel who also need to analyze the amplification results, including whether the Yin and Yang properties of the same batch of samples are under control, baseline setting, internal standard of hole by hole analysis and whether the sample results are normal.When all the Yin and Yang property controls meet the test requirements, and the possibility of false negative and false positive is excluded, the abnormal result samples shall be rechecked in time to ensure that there is no error before the final report and upload.These days, the inspectors in the PCR lab have been working overtime as the nucleic acid sample size has been increasing.The protective suit is airtight, so it gets hot when you put it on.In addition, the machine does not stop all the time, and the whole laboratory will be very hot and stuffy after a day of heat accumulation. Even if the air conditioner is turned on, the indoor temperature will reach 28-30℃.In addition, the static electricity in the laboratory is also very strong, and therefore very dry.Many people work in a “5+2” or “white + black” rhythm to get work done on time.Source: Healthy Binzhou