This description aims to provide patients with some useful information on the tests which may be included as part of their visit to the doctor. The tests are explained briefly. All results should be correlated with patient’s history and clinical findings. Therefore, your physician is the best person to interpret your laboratory results. Always consult your physician. For information on the coronavirus situation in Singapore, please visit the Ministry of Health website.
COVID-19 is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It is highly pathogenic (causes illness), virulent (has harmful effects) and spreads very quickly. The first reports of the disease were reported from Wuhan city, China.
The initial symptoms of COVID-19 are often similar to other respiratory illnesses, so testing is necessary to help diagnose a current or past infection. Learn more about the coronavirus from Dr Leong Hoe Nam, infectious disease specialist at Mount Elizabeth Hospital.
Method: Reverse Transcription Polymerase chain reaction (RT-PCR) — RT-PCR testing is commonly used to check for an existing SARS-CoV-2 infection. It detects the virus' RNA in a respiratory tract sample from a patient.
PCR is a laboratory method using a very small sample of DNA. It makes a very large number of copies of short sections of DNA, "amplifying" the DNA for detection. The reverse transcription step allows the viral RNA to be converted into DNA so that the PCR technique can be used.
Method: Blood Test for Antibodies (Total, IgG, IgM) to SARS-CoV-2 (Serology) — The body's immune system produces antibodies in response to SARS-CoV-2. By detecting the antibodies in a patient's blood sample, COVID-19 serology tests can indicate whether the patient has had the viral infection in the past. This test is NOT to be used for primary diagnosis of COVID-19 infection, RT-PCR remains the only accepted primary test method for diagnosis and confirmation of COVID-19 at this present time. In general, serology tests should not be used for patients with recent symptom onset (below 2 weeks), as antibodies are not detectable in the early phase of disease.
Antibody Test for IgM: When a virus attacks, IgM is usually the first antibody produced by the body’s immune system. When IgM is detected, it may mean that you have been infected and that your immune system has mounted a response to the virus. A positive IgM test indicates that you may still be infected, or you may have recently recovered from a COVID-19 infection.
Antibody Test for IgG: IgG antibodies remain in the blood after an infection has passed. These antibodies indicate that you may have had COVID-19 in the recent past. References: https://labtestsonline.org/tests/coronavirus-covid-19-testing