Many people think that if the nucleic acid is tested directly by a machine, the results will be obtained soon.But the reality is...

I've tried many times, why haven't the results come out yet?

In fact, after the medical staff samples your nose or pharynx, there are still seven or eight links for nucleic acid testing!

Let's take a look at how a complete nucleic acid report was born.↓

The first step, specimen collection

The nucleic acid test that citizens feel is actually just the first step in the whole process of nucleic acid testing——poke the nose, poke the throat, or both.

The second step, specimen transfer

Specimens collected at the sampling point need to be transported to the testing laboratory. The transporter needs to check the barcode information of each specimen, and then put it into a special and tightly packed transport box, and the surface of the transport box needs to be sterilized to avoid Cross-infection occurs during transit.

After the specimen is transferred to the laboratory, the inspection cannot be started immediately, and the information needs to be reconfirmed.

The third step, specimen acceptance and entry

After the handover is completed, the staff unpacks one by one, and manually enters the information of each specimen into the system. When entering information, a specimen needs to be handled 4 to 5 times.

At this time, the heart of precaution can not be relaxed at all. Inspectors are to identify the occurrence of empty pipes or spills. Especially in the 10:1 mixed collection of large groups, the small test tubes are crowded with swabs. Once the positive samples are spilled, on the one hand, it may cause contamination of other sample results (false positives), and on the other hand, it will affect the laboratory's results. Threats to biosecurity.

检验人员为刚刚送到的样本进行编号和信息录入工作

The entire input process of an information takes at least 1 to 2 minutes, which is to ensure the accuracy of each sample information. So rough statistics, the information input time of 100 people will take at least nearly two hours.

On the 16th and 17th, Shanghai conducted screening for key areas. A total of more than 14 million people were sampled to complete the test, and the number of samples on the 18th and 19th reached more than 21 million people.

The fourth step, extract nucleic acid

After the sample information is stored, professional technicians extract the nucleic acid from the sample, and then add the extracted nucleic acid to the amplification system.

According to different extraction reagent systems, it generally takes about 1 hour. This step requires inspection professionals to be wrapped and carried out in a biological safety cabinet. Sun Fenyong, vice president of Shanghai Tenth People's Hospital, said: "This step has high requirements for laboratory personnel, and it is also the step that has the greatest impact on the quality of the results in the nucleic acid detection process."

检验人员正在进行核酸提取环节中的加样步骤

So what is amplification?

Wu Wenjuan, director of the PCR laboratory of the Southern Hospital of Tongji University Affiliated East Hospital, said that if the nucleic acid extracted from the sample is regarded as a piece of land, and the COVID-19 virus is a seed, how do you know if there are seeds in the land? The simple way is to add some water and fertilizers (reagents) to change one seed to two, two to four, and four to eight..." Micro samples are not easy to detect, so it is convenient to make it more detection."

The fifth step, on-board detection

After adding the nucleic acid to be detected, the reaction system performs a fluorescent PCR amplification reaction. The time is slightly different depending on the PCR reagents and instruments used. Generally, it takes 90-120 minutes.

Once the instrument is started during the process, the amplification procedure cannot stop to add new samples, and the next batch of sample amplification must be completed after this batch is completed. This is one of the reasons why nucleic acid testing cannot be done on-the-go.

When the reaction tube is tested on the machine, it means "there is no turning back"——problems in any link from sampling to nucleic acid preparation may lead to rework and retesting, thus doubling the reporting time.

The sixth step, Review the results

After the nucleic acid amplification results are obtained, the laboratory personnel need to re-test the suspected positive samples in the results and the samples that have an impact on the interpretation of the results due to various reasons to ensure the reliability of the results. Generally, re-tests account for 1% of the total number of tests.

Once the test is repeated, you need to check the samples and repeat the fourth and fifth steps. These results need to be delayed for at least 2 hours.

The seventh step, quality assurance

In addition to the retested samples, the laboratory has a complete set of quality assurance procedures for nucleic acid testing. Once a suspicious quality problem occurs during the experiment, the possible links will be verified and reviewed, and these tasks will take up the original detection time. The most common is that if there is a suspected positive nucleic acid contamination of the experimental environment, the laboratory environment and instruments need to be completely disinfected immediately, and the possible nucleic acid contamination can be removed before continuing the experiment.

The eighth step, upload the results

In the final step, the staff uploads the results.This is the complete nucleic acid detection cycle.

Due to the recent large-scale nucleic acid testing in key areas in the city, and the requirement of multiple districts to work with negative test reports, the number of test samples has surged. They are racing against time to ensure quality and quantity.

这几天，检验人员都在超负荷工作

After so many steps,Delays are inevitable, The doctors have stepped up their horsepower,I hope you will understand and support more.Let's beat the epidemic together!

Source: Shangguan News, Xinmin Evening News, Chatbox, etc.