The Doubt of ＂False Negative＂ in Nucleic Acid Detection： Fine-tuning the diagnosis and treatment plan and increasing ＂clinical diagnosis＂

　　Wu Juan, who lives in Qingshan District, Wuhan, never expected his father to get a positive result of nucleic acid test.

　　Wu Juan’s father has been waiting for a definite diagnosis — — If novel coronavirus was not diagnosed with pneumonia (hereinafter referred to as "COVID-19"), he would not be admitted to hospital. Because of repeated fever, Wu Juan’s father has been weak and unable to stand.

　　The problem faced by Wu Juan’s family is not unique. As the "gold standard" for COVID-19’s diagnosis, the detection of viral nucleic acid has been false negative in practice.

　　Xu Shunqing, vice president of the School of Public Health, Huazhong University of Science and Technology, said at a press conference in Hubei Province on the evening of February 9 that novel coronavirus mainly invaded the lungs, so there was a certain false negative in nucleic acid detection, that is, some patients were not detected, that is, missed diagnosis, which may cause some sources of infection not to be really identified, and there is a risk of expansion.

　　But at the same time, it is very important to screen out the confirmed patients in the shortest time and then treat them centrally, which is still in the high incidence period of the epidemic. At present, nucleic acid detection still plays a very important role in the process of diagnosis.

　　Li Taisheng, director of the Department of Infectious Diseases of Peking Union Medical College Hospital who participated in the prevention and control of SARS in 2003, said in an interview with The Paper that COVID-19 could be diagnosed as soon as possible through nucleic acid detection, which is more favorable than the prevention and control in 2003.

　　At the same time, with the adjustment of the national diagnosis and treatment plan and the attention of many medical experts, the loopholes caused by false negative nucleic acid testing are shrinking.

　　"After the discovery of this problem, National Health Commission began to use CT and clinic as the basis for the trial of the fifth edition of COVID-19’s diagnosis and treatment plan. Now the judgment of the condition is not only the appearance of positive nucleic acid test, but also the clinical standard. There has been no fever for three consecutive days, and CT imaging has improved. These three aspects are combined." Xu Shunqing said on the evening of February 9.

　　At noon on the 11th, Wu Juan v. The Paper, and his father was admitted to the centralized isolation point in Qingshan District on the 10th. They are still waiting for the results of their father’s second nucleic acid test. Because of the limited medical conditions at the isolation point, my father still has to go to the Ninth Hospital of Wuhan for injections every day after living in the isolation point.

　　A "door" that must be passed for diagnosis.

　　Wu Juan realized the seriousness of the epidemic from the "city closure" in Wuhan. But she never imagined that the haze of the epidemic would come to her family.

　　On January 26th, the second day of the first month, Wu Juan’s father developed symptoms such as waist ache, fatigue and cough. At this time, it has just been three days since Wuhan "closed the city".

　　In order to buy anti-inflammatory drugs for his father, Wu Juan went to the drugstore near his home, but he didn’t get any. Even oseltamivir for treating influenza was sold out. In desperation, she had to buy 10 boxes of children’s version of oseltamivir for her 71-year-old father.

　　At this point, my father is still very stubborn. He always thinks that his symptoms are just a cold caused by falling asleep while opening the window for air. Until February 3, my father didn’t take medicine, and his physical discomfort became more and more serious.

　　On the morning of February 4th, my father was too tired to get up, and his face was red. His temperature was measured at 37.4 C. After going to a community clinic in Qingshan District for routine blood tests, he found that his white blood cells and lymphocytes were low, accompanied by fever. The community hospital suggested that he be sent to the General Hospital of China Resources WISCO for CT examination.

　　On the same day, the CT diagnosis was infectious lesions of both lungs, and the doctor thought it was viral pneumonia. He was prescribed oseltamivir and Lianhua Qingwen granules, and suggested that he go home and observe in isolation. If the high fever is above 38.5°C, he should go to the hospital again.

　　Despite the CT diagnosis results, according to the "Diagnosis and Treatment Plan for Pneumonia Infected by novel coronavirus (Trial Fourth Edition)" issued by National Health Commission at that time, the confirmed cases should be "real-time fluorescent RT-PCR for novel coronavirus nucleic acid detection", which simply means that the nucleic acid detection results are positive.

　　This has become a "door" that Wu Juan’s father must open if he can be diagnosed.

　　"False Negative" Doubt Cloud

　　On the evening of February 4th, Wu Juan’s father had a high fever of 39 C.

　　Wu Juan hurriedly sent his father to the General Hospital of WISCO. Although the hospital is not a designated hospital, it is close to home. The doctor prescribed the medicine for 10 days, and he could only infuse it in the outpatient department. Fortunately, that night, the doctor told me that I could come to the hospital for nucleic acid testing the next morning, and Wu Juan felt that there was hope again.

　　However, the next day, when they arrived at the General Hospital of WISCO on time, the fever clinic doctor said that there were only 20 nucleic acid detection reagents that day, and Wu Juan’s father’s name was not on the registration list. The reagents on that day had been used up, and it would take another day to go to the hospital for testing.

　　Because of repeated fever, Wu Juan’s father was unable to stand, so he had to rest in the corridor of the hospital.

　　Wu Juan said that on the same day, just a leader went to the General Hospital of WISCO to inspect the epidemic prevention and control work. When she saw her father crouching in the hospital corridor, she went forward to understand the situation, and then arranged for the elderly to take the "green channel", and finally achieved the key step of diagnosis — — Nucleic acid detection.

　　Only when the nucleic acid test is positive can the diagnosis be considered, and it is possible, qualified and hospitable for the father. "But what if it’s not positive?" Wu Juan was still worried.

　　In fact, her worries are not groundless. The false negative of COVID-19 virus nucleic acid test has surfaced one after another.

　　On the evening of February 5th, Wang Chen, vice president of China Academy of Engineering and president of China Academy of Medical Sciences, said that not all patients can detect nucleic acid positive, and only 30% to 50% of patients are infected with novel coronavirus. There are still many false negatives by collecting throat swabs from suspected cases.

　　On the evening of February 6th, Li Wenliang of central hospital of wuhan Eye Hospital, which attracted the attention of the whole network, was critically ill and died after several hours of rescue. According to the Weibo released by Li Wenliang before his death, he was officially diagnosed after three nucleic acid tests, and the results of the previous two nucleic acid tests were negative.

　　At noon on February 7th, Wu Juan’s father’s first nucleic acid test results came out, showing negative results. But at this point, my father still has a high fever and his consciousness is a little blurred. In the afternoon, her father went to WISCO General Hospital again for blood routine and CT examination, and the CT image diagnosis was more serious than the first time.

　　The doctor suggested that Wu Juan’s father go to No.9 Hospital for reexamination, because the General Hospital of WISCO does not belong to the designated hospital, and COVID-19 could not be judged to be false negative, and she was given a notice of transfer.

　　On the morning of February 8th, Wu Juan’s father went to the Ninth Hospital of Wuhan, and showed the test results to the doctor, but he had to wait for infusion in the outpatient department first.

　　The community is also working hard. On the morning of February 9, after receiving a phone call from the community staff, Wu Juan took her father to the Ninth Hospital for the second nucleic acid test, and the results could be obtained in about two to three days. She said that she even expected her father’s nucleic acid test result to be positive, so that she could be hospitalized as soon as possible.

　　In an interview with The Paper, Zhou Xin, the leader of the first group of experts supporting Hubei medical team, also said that false negatives also involve many aspects, including differences in respiratory sensitivity of different people, differences in sampling methods and differences in production of different kit companies, and all kinds of reasons may lead to false negatives.

　　Here comes the "supplementary plan"

　　The appearance of false negative in nucleic acid test also makes the diagnosis and treatment plan for COVID-19 be fine-tuned.

　　After the outbreak, the "Diagnosis and Treatment Plan for Pneumonia Infected in novel coronavirus" was constantly updated at the national level, and the fifth trial version was released as of February 5. This version of the diagnosis and treatment plan distinguishes Hubei Province from other provinces outside Hubei Province in case diagnosis.

　　Other provinces outside Hubei are still divided into "suspected cases" and "confirmed cases". However, the classification of "clinical diagnosis" has been added in Hubei Province. The standard of "suspected case" is revised as follows: whether there is epidemiological history or not, as long as it meets the two clinical manifestations of "fever and/or respiratory symptoms" and "normal or decreased white blood cell count or decreased lymphocyte count at the early stage of onset", it can be considered as a suspected case. It is equivalent to relaxing the standard of suspected cases. Suspected cases with imaging features of pneumonia are clinically diagnosed cases. The diagnostic criteria for confirmed cases have not changed.

　　The problem of missed diagnosis caused by false negative nucleic acid detection is also attracting the attention of experts.

　　On the evening of February 9th, at the press conference held in Hubei Province, Xu Shunqing, vice president of the School of Public Health of Huazhong University of Science and Technology, said that the main part of novel coronavirus’s invasion was the lung, so there was a certain false negative in nucleic acid detection, that is, some patients were not detected, that is, missed diagnosis, which might cause some infectious sources not to be really identified and there was a risk of expansion.

　　Xu Shunqing believes that after this problem was discovered, the trial of the fifth edition of the diagnosis and treatment plan was based on clinical symptoms such as CT detection. Now the judgment of the condition is not only the appearance of positive nucleic acid detection, but also the clinical standard. There is no fever for three consecutive days, and CT imaging has improved. These three aspects are combined.

　　Li Qing, a native of Wuhan, is the beneficiary of the above-mentioned fifth edition of the diagnosis and treatment plan.

　　On February 3rd, Li Qing’s parents-in-law and grandmother went to tongji hospital, affiliated to Huazhong University of Science and Technology, for a nucleic acid test. The results showed that their mother-in-law and grandmother were nucleic acid positive, and they were hospitalized after COVID-19 was diagnosed.

　　However, the results of CT showed that Gonggong was the most serious lung infection among the three people, and it spread, but the results of nucleic acid test showed negative, so the doctor asked him to queue up again for nucleic acid test.

　　Li Qing told The Paper that her father-in-law was admitted to the hospital on February 7th because he developed serious infection symptoms and was judged by clinical diagnostic criteria.

　　For COVID-19 patients in Hubei Province, if there are no serious symptoms, in order to reduce the risk of infection, the trial of the fifth edition of the diagnosis and treatment program requires medical staff at all levels and types of medical institutions to immediately conduct isolation treatment after discovering suspected diseases and clinically diagnosed cases that meet the definition of cases. Suspected cases and clinically diagnosed cases should be isolated in a single room, and specimens should be collected as soon as possible for pathogen detection.

　　The discharge standard is no longer single.

　　The 70-year-old mother of Wuhan native Liu Tong was admitted to the isolation ward because the results of two nucleic acid tests were negative and she could not be diagnosed, but she had certain symptoms of lung infection.

　　His mother became ill on January 23rd. After becoming a suspected case, Liu Tong’s mother was isolated in the ward of the Eighth Hospital of Wuhan. From January 26 to now, she has done two nucleic acid tests, and the hospital has not informed him of the results. However, the hospital announcement showed that it was negative if it was not notified within 48 hours, and he acquiesced that the mother’s result was also negative.

　　Liu Tong’s mother’s previous CT examination showed bilateral lung infection. What worries him more is that because he is not a confirmed patient, his mother is not living in an isolation ward with a single room, but in a six-person room, which is full of people who can’t be diagnosed like his mother. Liu Tong is worried that if there is a false negative, there will be cross-infection.

　　Fortunately, his mother’s current physical condition tends to be stable, but the epidemic is still in a high incidence period. Chen Tong can’t confirm whether her mother can leave the hospital, and whether she is not a COVID-19 patient and is not contagious. "I can only stay for a few more days." He said.

　　For discharged patients, nucleic acid detection is also a necessary procedure. The trouble of false negatives also exists.

　　In the trial fourth edition and the previous "Diagnosis and Treatment Plan for Pneumonia Infected by novel coronavirus", the criteria for COVID-19 patients to be released from isolation and discharged are that their body temperature has returned to normal for more than 3 days, their respiratory symptoms have obviously improved, and their respiratory pathogenic nucleic acid tests have been negative for two consecutive times (the sampling interval is at least 1 day), and they can be released from isolation and discharged from hospital or transferred to corresponding departments for treatment of other diseases according to their illness.

　　If the results of two consecutive nucleic acid tests for infected people are false negative, it will affect the judgment of recovered patients.

　　The corresponding supplement appeared in the trial fifth edition of "Diagnosis and Treatment Plan for Pneumonia Infected in novel coronavirus". The discharge standard of this scheme has increased, and it is necessary to judge whether it can be discharged from hospital from three aspects: nucleic acid detection, clinical symptoms and lung imaging.

　　Zhou Xin told The Paper that, generally speaking, patients can basically leave the hospital safely if they meet twice negative nucleic acid tests. It will be more scientific and safe to go home for two weeks after discharge.

　　"To reduce false negatives, the sampling should be accurate and the sampling method should be correct." Zhou Xin said that for the sampled medical staff, it is necessary to undergo standardized training. Sputum coughed by patients can be sampled, and lavage fluid can also be used for nucleic acid detection. If samples of deep respiratory tract can be obtained, its sensitivity and specificity are very high. For most patients, it can be accurately detected.

　　Li Taisheng, director of the Department of Infectious Diseases of Peking Union Medical College Hospital, who participated in the prevention and control of SARS in 2003, admitted in an interview with The Paper that COVID-19 could be diagnosed as soon as possible through nucleic acid detection, which is more favorable than the prevention and control in 2003.

　　Wu Juan v The Paper. On the morning of February 10th, his father was admitted to the centralized isolation point in Qingshan District. They are still waiting for the results of their father’s second nucleic acid test.

　　(Wu Juan, Li Qing and Liu Tong are pseudonyms, and intern Yan Caiqi also contributed to this article. )