Article is from WeChat public account: Digital Visual (ID: VDataWorks) , Data Editing: Jiang Liu, Hua Yihe
On February 5, 2020, the National Health and Health Commission released the “Pneumonitis Diagnosis and Treatment Program for New Coronavirus Infection (trial version 5) ” Among them, the standard for suspected cases in Hubei Province was relaxed: those suspected cases with pneumonia imaging characteristics are clinically diagnosed cases. Earlier, many first-line imaging doctors in Wuhan proposed that the positive diagnosis of new coronary pneumonia should be based on CT lung film test instead of nucleic acid test as soon as possible.
The dispute between “nucleic acid test” and “CT confirmed diagnosis” directly points to the shortage of reagents, false negative results of reagents, and fewer institutions with testing qualifications. Among them, the shortage of reagents is the key to ensure the efficiency of diagnosis. But is “insufficient reagent volume” the only factor holding back the rate of diagnosis? After the standards for suspected cases are relaxed, will the efficiency of diagnosis be changed?
Hubei has only detected 200 copies per day
The improvement of diagnosis efficiency in Hubei Province, with January 16 as the dividing line.
Before January 16, there were no kits in Hubei Province. The samples even had to be sent to a nationally designated testing agency for testing in Beijing. The results returned in about 3 to 5 days. On January 16, after the Hubei Provincial Center for Disease Control and Prevention received the kit issued by the state, it began to conduct pathogenic testing on specimens of patients with unexplained viral pneumonia submitted for examination in Wuhan.
According to public reports, from January 16 to January 22, the process of detecting suspected cases in Wuhan is as follows.
After receiving the kit issued by the state on January 16, according to the number of 200 that can be tested per day, as of January 22, the acceptable testing capacity of Hubei Province has barely reached 1200 copies, according to the cumulative Hubei Province that day Of the 444 confirmed cases, a rough estimate of the diagnosis rate at that time was 37%-this is basically in line with the “early 38%” diagnosis rate announced by the Hubei Provincial Government at a press conference on February 1.
This shows that the testing organization was running at full capacity. With the spread of the disease and the increase of suspected cases, the testing capacity of 200 copies per day could not meet the actual needs.
Production of nucleic acid reagents increased after special approval
In order to improve the efficiency of diagnosis, the State Drug Administration has approved 7 companies on January 31. (Zijiang Biotechnology, Shengxiang Biotechnology, Huirui Biology, Geneno Bio, Berger Medical, Daan Gene, BGI Gene) Research and development of new crown virus nucleic acid detection reagents, prompting them to enter mass production as soon as possible. According to the normal speed of approving medical devices, the time for approval of medical devices by the FDA is two years.
With the green light of policies, the production capacity of various enterprises has risen sharply.
Why nucleic acid reagents are so important
But in the opinion of experts advocating the replacement of nucleic acid reagents with CT lung films, the quality of nucleic acid detection kits is uneven. Currently waitingThe number of nucleic acid detections greatly exceeds the detection capacity; doctors who support nucleic acid reagents believe that nucleic acid detection is still the “gold standard” that must be adhered to, and CT imaging alone cannot truly confirm the diagnosis.
How does the controversial nucleic acid reagent work, and why is it so important?
A nucleic acid reagent is a more accurate method of detection than a method such as pathogen isolation. The researchers will first study the sequence of the coronavirus, and then develop specific fluorescent primers that can be combined with this virus sequence. The designed primers will be combined with specific DNA fragments obtained by retrovirus coronavirus and polymerized in DNA. With the help of the enzyme, the target fragment is continuously extended, and the newly synthesized DNA fragment carries a fluorescent signal.
After the reagent is applied to the test, if the sample provided by the tester contains a virus-specific fragment, a fluorescent signal is displayed, which means that the tester carries a coronavirus.
From the extraction to the amplification result, the process of detecting the virus by the nucleic acid reagent may only take half a day. At a press conference held on January 19, Huang Chaolin, an expert from the Hubei Provincial Medical Group and vice president and chief physician of Wuhan Jinyintan Hospital, stated that The Hubei Provincial Center for Disease Control and Prevention used the nationally issued viral nucleic acid detection reagents After the box, more than 100 confirmed cases were added within two days.
Can I pass this level with the help of CT diagnosis?
While the number of kits has soared, Wuhan residents still report that it is difficult to diagnose. The reason is that in the process of testing, in addition to test factors such as reagents, there are also non-test factors such as laboratories, instruments, and personnel.
Since the country has incorporated pneumonia of the new coronavirus into a Class B infectious disease and adopted Class A management, the samples of this type of pathogen are detected according to highly pathogenic pathogenic microorganisms （第Type 2) for management. Laboratories that can detect the virus have fairly high standards. On January 22, Wuhan released 10 laboratories capable of detecting pathogenic nucleic acids, and Hubei Province has been expanding the number of laboratories.
Can the rapidly expanding inspection agencies meet the inspection needs? The official did not disclose no specific demand-side numbers for comparison, but there is such a set of numbers that can be calculated:
On January 29, Hubei’s full-load testing organization had a capacity of 6,000 tests, and the number of newly diagnosed people in Wuhan reached 1,032 on that day. If you divide the number of confirmed diagnoses by 1,032 people by the detection capacity of 6,000 copies, you will get a rate of 17.2%. This is again the same as the “The diagnosis rate in recent days is only about 18%.” “Are consistent. This shows that the number of testers is completely limited by the maximum number of testers.
The diagnosis rate should be equal to the number of people diagnosed / the total number of people tested. It ’s like 100 people doing a physical examination. The daily test volume of the instrument is 200 people. 10 people have detected a disease. The method of calculating the diagnosis rate is 10/100. Instead of 10/200. If the diagnosis rate is also equal to the number of confirmed patients / the maximum number of tests, the total number of testers and the maximum number of tests are the same.
In other words, The reason why Hubei is able to diagnose so many people is because the detection capability allows only so many people to be detected; even if it is significantly increased compared to the previous detection volume, it still cannot meet the detection needs. After the mass production of nucleic acid reagents, the number of detection institutions has become another shortcoming.
At the same time, there is also a shortage of professional PCR talents. According to the Beijing News, more than 220 people participated in the technical training of gene amplification laboratory in Hubei province the year before last year, which increased to 268 people last year. In the face of tens of thousands of cases of infection, this number is tantamount to a drop in the bucket.
The nucleic acid detection process of new coronary pneumonia requires the latest research reagents, rapid policy guarantees, rapid mass production, cutting-edge laboratory conditions and large numbersProfessionals. No wonder some experts in the field of imaging have called for the use of “positive CT lung film test” instead of “positive nucleic acid test” as a basis for clinical diagnosis.
The Hubei Provincial Epidemic Prevention and Control Command issued a task letter on February 2 requiring medical testing institutions to issue a “Military Warrant” to maximize testing potential and digest the stock within 2 days; on the 5th, Hubei Province increased the “clinical diagnosis “, And relaxed the criteria for” suspected cases “: those with suspected cases with imaging characteristics of pneumonia are clinically diagnosed cases. A two-pronged approach is only to improve the efficiency of diagnosis. Can the news around the beginning of spring bring a new hope to the patients who have been diagnosed in the cold winter?
Article is from WeChat public account: Digital Visual (ID: VDataWorks) , Data editing: Jiang Liu, Hua Yihe