Samples for COVID-19 testing by RT-PCR should be taken as soon as symptoms start and from different sites of the body to have the best chance of correct diagnosis.

Problem

Accurate testing for coronavirus (SARS-CoV2) is essential for controlling COVID-19. The success of testing depends on using the most accurate tests at the most appropriate times. Testing for active coronavirus relies predominantly on the reverse transcription polymerase chain reaction (RT-PCR) method that detects viral genetic material. However there are concerns that the volume of viral material can vary in samples collected from different parts of the body and at different times during the course of the disease. This could lead to inaccurate test results.

Action

• Working within a national, synergistic collaboration we produced a systematic review of 32 studies with data from individual participants with confirmed SARS-CoV2, tested at multiple times during their infection by RT-PCR.
• The study was led by Sue Mallet (University College London) and involved collaboration with 6 universities, Kleijnen Systematic Reviews Ltd and the Frimley Health NHS Foundation Trust.
• We used robust methods to synthesise published literature and identify patterns that would not be possible from individual articles.

Outcome

• Our analysis indicated that the sample site within the body, and the time of testing during the condition, influences whether infected individuals are identified by RT-PCR molecular tests.
• To avoid the consequences of missed infection, we recommend that samples for RT-PCR molecular testing should be taken as soon as symptoms start.
• We also suggest using lower respiratory tract (e.g. sputum) or faecal samples if a patient has had symptoms for more than 10 days.

Impact

• This review provides the research community with a solid knowledge base of the pandemic.
• Using our recommendations, some hospitals in the UK now routinely take RT-PCR samples from multiple sites, such as the nose and throat.

To read the full published article visit this link.