Pcr test nasal swab and an antigen test difference for covid 19

What is COVID-19?COVID-19 is an epidemic disease caused by SARS-CoV-2. An acute respiratory infectious disease broke out at the end of 2019. So far, WHO has been making the latest tracking report on the new pneumonia on the Internet every day.

What are the current methods of COVID-19 test?

Virus detection includes two types: nucleic acid amplification test (NAAT) (PCR test) and antigen test.

Antibody tests (also known as serological tests) can prove whether you have been infected in the past.

What is the COVID-19 PCR test?

PCR (polymerase chain reaction): similar to the natural replication process of DNA, its specificity depends on oligonucleotide primers complementary to both ends of the target sequence.

Basic principle: the basic principle of PCR technology is similar to the natural replication process of DNA. Its specificity mainly depends on the oligonucleotide primers complementary to both ends of the target sequence. It consists of three basic reaction steps: denaturation, renaturation and extension.

PCR test sample collection method include:

If the sample contains a virus, the researchers will extract its RNA.

Why use the PCR test ?

PCR nucleic acid examination is a direct detection of COVID-19 RNA in human body by sampling from the nasal cavity. The structure of virus is composed of DNA or RNA combined with external lipid protective capsule. Therefore, direct detection of virus DNA itself is the most accurate, fastest and effective new detection method. PCR nucleic acid test can detect infection immediately after the human body obtains the virus, and the accuracy is much higher than antibody test.

ABOUT PCR TEST_Pcr test nasal or Throat swab sampling

How does the PCR test nasal swab work?

Nasopharynx swab is to wipe the secretion of the patient’s nasal cavity or pharynx. And then make the secretion into smear for examination and bacterial culture to clarify what bacterial infection is in the patient’s nasal cavity and pharynx.

Nasal swab sampling procedure

1. Keep the patient’s head still and remove the secretions on the middle surface of the anterior nostril;

2. Gently and slowly insert the swab through the nasal cavity to the nasopharynx;

3. After encountering resistance, it reaches the posterior nasopharynx and stays for several seconds to absorb secretions;

4. Gently rotate and take out the swab and place it in the transport medium;

5. For the swab used for virological test, immerse the swab head into the virus delivery medium, discard the tail, and tighten the tube cover;

If it is necessary to collect from both nostrils, the sampler should use the same swab.

How does the antigen test work?

Rapid antigen detection can play an important role in guiding patient management, public health prevention and control decision-making and covid-19 monitoring.

It is especially valuable for grass-roots areas that may hinder clinical diagnosis and control due to lack of nucleic acid detection capacity or long detection time.

According to WHO, high specificity based on antigen detection indicates that the positive results indicate new crown virus infection.

For patients within 9 days of onset, sampling personnel can use antigen detection as a diagnostic test.

Especially for the staff of medical institutions, inpatients and visitors in the epidemic area.

When nucleic acid detection cannot be effectively implemented, antigen detection can be used as an important screening method.

Rapid antigen test sampling procedure.

Rapid antigen test sampling process

Generally speaking, nucleic acid detection: it has high requirements for laboratory environment, detection personnel and instruments. The detection has high sensitivity and good specificity.Generally, we can get the results in 2-3 hours.

Antigen detection: it has low requirements for the laboratory. For early screening and early diagnosis. It is suitable for large-scale screening in grass-roots hospitals. we can obtain the results within 15 minutes at the fastest.

At present, PCR test nasal swab is widely used, and the sensitivity and specificity of antibody / antigen detection reagents are still limited.

Each has its own emphasis and cannot replace each other. We should combine multiple virus detection methods.

It can effectively shorten the detection window period and improve the positive detection rate.