Discordant results of SARS-CoV-2 PCR-based tests in the early phase of pandemic in Indonesia: Infection control consequences

INTRODUCTION: Growing evidence suggest that cycle threshold (CT)-value of reverse transcription polymerase chain reaction (RT-PCR) is correlated with transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and some kits set different CT-value cut-off. This report presents the discordant results of two widely used RT-PCR kits in Indonesia due to different CT-value cut-offs and highlights its potential consequence in SARS-CoV-2 containment. METHODS: Nasopharyngeal swab samples with SARS-CoV-2 negative with a RT-PCR kit (manufacture pre-set CT-value cut-off was 35 amplification cycles) were retested with another RT-PCR kit with a higher pre-set CT-value of 40 amplification cycles. All procedures were performed according to the manufacturer protocols. RESULTS: In total, 30 samples with SARS-CoV-2 negative for the first kit were retested. We found that 25 out of 33 samples (75.5%) were positive using the second RT-PCR kit that had a higher manufacture pre-set CT-value cut-off. In addition, among 500 RT-PCR tests using the first RT-PCR kit, 103 of them (20.6%) were categorized as inconclusive results based on the second manufacturer’ guideline. DISCUSSION AND CONCLUSION: Our data suggest the possibility of discordant results of SARS-CoV-2 detection due to different pre-set cut-offs by the companies. As consequence, this could leave a fraction of individuals who were misclassified that could act as source of virus transmission within community.