UNDERSTANDING SARS-COV-2 RT-PCR TEST RESULTS

Laboratory confirmation of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19) is crucial in the pandemic response. To date, detection of unique viral sequences (genetic material) using nucleic acid amplification tests (NAATs) primarily through Real-Time Reverse Transcription Polymerase Chain Reaction (rRT-PCR), is considered by the World Health Organization (WHO) as the standard method for laboratory diagnosis of SARS-CoV-2. Relative to other detection methods, Real-Time PCR enables sensitive and specific detection of the SARS-CoV-2 viral RNA from clinical material in extremely minute amounts. Virus propagation (virus culture) from clinical specimens provides definitive confirmation of the presence of infectious virus. But it requires Biosafety Level 3 facilities, advanced technical competencies and training, and its turnaround time is not suitable for rapid response (Singanayagam et al., 2020). Current evidence shows that rRT-PCR-based methods for diagnosis of SARS-CoV-2 have sufficient sensitivity to detect viral infection in symptomatic individuals, in pre-symptomatic individuals (before onset of symptoms) and in asymptomatic cases (no symptoms reported), provided timely, adequate and quality-assured specimen collection, laboratory analysis and interpretation of results (World Health Organization, 2020). PCR-based diagnostic tests are considered as complex testing systems, with multiple factors affecting the outcome of a PCR test, an rRT-PCR test result should not be used as the sole criterion for patient management and disease transmission control interventions (Tahamtan et al, 2020). Each test result should always be interpreted along with available clinical and epidemiological information.