Coronavirus (COVID-19) tests

What is analysed?

Coronavirus (COVID-19) tests analyse the presence of the virus SARS-CoV-2, which causes COVID-19.

COVID-19 tests include:

The PCR (polymerase chain reaction) test: Analyses the genetic material of the SARS-CoV-2 virus. The test detects the presence of viral RNA to confirm an active infection. The antigen test: Analyses the presence of specific viral proteins (the nucleocapsid or spike proteins) from the SARS-CoV-2 virus. The antibody test: Analyses the presence of immunoglobulin M (IgM) and/or immunoglobulin G (IgG) antibodies in the blood, which are produced by the immune system in response to a past or current infection with the SARS-CoV-2 virus.

What does the result mean?

The PCR test and the antigen test: The result indicates whether the patient is currently infected with the SARS-CoV-2 virus. The antibody test: The result indicates whether the patient has been exposed to the virus and has developed an immune response.

Why conduct the analysis?

The PCR test: The test is conducted for the diagnosis of SARS-CoV-2 infection. The antigen test: The test is conducted for the detection of some of the proteins of the SARS-CoV-2 virus, indicating the presence of viral particles. The antibody test: The test is conducted for the detection of antibodies against SARS-CoV-2, which indicate that the patient has been previously infected with SARS-CoV-2.

When to conduct the analysis?

The PCR test and the antigen test: The tests are conducted when symptoms of COVID-19 due to SARS-CoV-2, such as fever, cough, shortness of breath, loss of taste and smell, are observed. The tests may also be conducted when a patient with or without symptoms has been in contact with a patient who is infected. The antibody test: The test is conducted when a patient has had COVID-19 or suspects they may have had it and their doctor wants to confirm the presence of antibodies against the virus, especially if the patient was asymptomatic.

What sample is required?

The PCR test and the antigen test: A respiratory sample, obtained through a nasal or throat swab, is required. The antibody test: A blood sample is required. The blood is drawn from a vein, usually in the arm.

Is any prior preparation necessary?

The PCR test: No specific prior preparation is necessary. The antigen test: No specific prior preparation is necessary. The antibody test: Patients should fast for 8-12 hours before the blood sample is taken. In addition, patients should also inform a healthcare professional about any medications being taken, as they could affect results.

How is it performed?

The PCR test: The sample is sent to a laboratory, where the viral RNA is extracted and amplified using the PCR technique allowing for the detection of viral genetic material. The antigen test: The sample is analysed on-site, using a lateral flow assay or other rapid testing methods. The antibody test: The sample is sent to a laboratory, where it is analysed to detect the presence of IgM and/or IgG antibodies.

What are the normal values?

The PCR test: A negative result indicates no detection of SARS-CoV-2 RNA, suggesting no active infection or that the viral load is below the detection limit. The antigen test: A negative result indicates no detection of SARS-CoV-2 antigens, suggesting no active infection or that the viral load is below the detection limit. The antibody test: A negative result indicates no detectable antibodies, indicating no past infection or immune response.

What does having altered values mean?

The PCR test: A positive result indicates the presence of SARS-CoV-2 RNA, showing an active COVID-19 infection. The antigen test: A positive result indicates the presence of SARS-CoV-2 antigens, indicating an active COVID-19 infection. The antibody test: Positive IgM and IgG results indicate a combined immune response. A positive IgM result indicates a recent or ongoing infection, whilst a positive IgG result indicates a past infection.