First of all what is the definition of "gold standard"? The so-called "gold standard" refers to the most authoritative diagnostic standards, the new crown test mainly has three kinds of methods: new crown nucleic acid rapid test, antibody testing and antigen testing, and new crown nucleic acid rapid test is the "gold standard" for its diagnosis, someone only new crown nucleic acid rapid test positive to say that he (or she). The rapid nucleic acid test is the "gold standard" for diagnosis, and a person can only be said to be a confirmed patient if he or she has a positive nucleic acid test; otherwise, even if the CT and MRI images are clear, they can only be considered positive.
First, the expression of diagnostic principles was added. It is emphasized in the diagnostic principles that a comprehensive judgment should be made based on the epidemiological history, clinical manifestations and laboratory test results.
Second, a positive rapid nucleic acid test for new coronavirus is the primary criterion for confirming the diagnosis. The new coronavirus-specific antibody test for those who have not received the new coronavirus vaccine can be used as a reference basis for diagnosis. (In principle, antibodies are not used as a diagnostic basis for those who have received the novel coronavirus vaccine and those with previous novel coronavirus infection.)
The current technique for rapid detection of new coronaviruses is fluorescent quantitative RT-PCR (polymerase chain reaction) for the rapid detection of new coronaviruses (beta genus coronaviruses, single-stranded RNA viruses). It has been reported that the order of detection rate for rapid detection of neo-coronavirus in respiratory samples is lung tissue (gold standard) > bronchoalveolar lavage fluid (BALF) > aspirated sputum or cough sputum > nasopharyngeal swab or oropharyngeal swab > nasal swab. In our daily testing, rapid New Coronary Nucleic Acid testing using pharyngeal swabs and nasal swabs is the more common way.
And why use the new crown nucleic acid rapid test technique as the gold standard?
Because nucleic acid (DNA or RNA) is the genetic material of viruses, and any species has unique nucleic acid (DNA or RNA) sequences, so nucleic acid testing of the characteristic sequences of the new coronavirus can tell whether or not you are infected with new coronavirus.
The purpose of the rapid nucleic acid test for neo-crown is to amplify the trace amount of viral DNA in the sample by (35-40 times of 2), making it possible to detect the concentration read by the testing device.
However, whenever a fluorescent quantitative PCR assay is performed, there exists a limit of detection (LOD, limit of detection, also known as limit of detection), so sequencing of the sample for detection may be considered, and detection of IgM and IgG antibodies to the new coronavirus has been initiated.
In clinical significance: novel coronavirus IgM is the earliest antibody to appear in the initial humoral immune response. elevated IgM in serum indicates a new infection and can be used for early diagnosis of novel coronavirus infection in the acute phase. IgG antibody testing is used to confirm the infection status of a case.
In conclusion, more sensitive rapid nucleic acid detection methods for new coronaviruses such as digital PCR have also been used, and the new coronavirus antibody test can be used as a complement to the fluorescent quantitative RT-PCR nucleic acid test, and their combined testing will significantly improve the sensitivity of the test, greatly reduce the false-negative rate, and decrease the rate of misdiagnosis or missed diagnosis.
