What's the difference between a throat swab and a blood sample

2020/08/10

The current methods for detecting COVID-19 include nucleic acid testing, blood test, and combined lung CT. So what is the difference between a new crown detection throat swab and a blood draw? Let's take a look together.

New coronavirus testing is currently mainly divided into two types: nucleic acid testing and (blood) antibody testing. Generally speaking, in clinical diagnosis, a joint test of the two will be used to determine whether the tested person is infected with the virus and the stage of the disease.

The specimens for the new crown nucleic acid test are collected from the secretions of the respiratory tract, and the virus ribonucleic acid (RNA) in the patient’s secretions is tested to see if it is infected by the virus. The blood samples are collected from the patient's blood, which is used for antibody testing to see if there are antibodies stimulated by the virus in the patient's blood, and to detect whether the patient is infected by the virus and the stage of the disease. Nucleic acid positivity is related to viral load. The higher the viral load, the greater the possibility of nucleic acid positive. In theory, viral nucleic acid can be detected within 1 to 2 days of infection.

No matter what the disease is, blood test is an indispensable item in clinical diagnosis and treatment. For the new coronavirus, routine blood tests can help doctors first identify bacterial infections or viral infections. If the patient's blood routine tests have a normal or reduced peripheral blood white blood cell count and a decreased lymphocyte count, then it is most likely a viral infection, and then combined with the patient's epidemic Only with the disease and symptoms, the doctor can judge whether the patient is a suspected case of new coronavirus infection, and then there will be follow-up viral nucleic acid testing. So in this respect, blood testing is also helpful for the investigation of the new coronavirus.

The new coronavirus nucleic acid test results are an important reference for the diagnosis and efficacy evaluation of new coronavirus pneumonia. Nucleic acid test screening samples are mostly derived from deep cough sputum or throat swabs. Because the oropharyngeal swab can be operated by opening the mouth, it is relatively simple, so it is more commonly used clinically. However, if the collection of throat swab nucleic acid test specimens is not standardized, it may cause "false negative" results and cause delays in treatment. Therefore, nucleic acid and blood drawn antibody tests need to complement each other to confirm whether infection has occurred and the status of the patient.