Cycle threshold values versus reverse transcription-polymerase chain reaction positivity in COVID-19 de-isolation

Abstract

In the modern COVID-19 pandemic, reverse transcription-polymerase chain reaction (RT-PCR) positivity has a major role in the diagnosis of the disease. However, in deciding the patient's discharge or de-isolation, its role is still debatable. We are, hereby, describing three cases (an intern, a nursing officer and a caretaker of another patient) where only RT-PCR could not help much since it was persistently positive for >20 days of the illness course. Instead, the cycle threshold (Ct) values could have better correlated with the infectivity of COVID. We propose a rising trend (24 h apart) and absolute Ct value > 25, instead of RT-PCR negativity (which was taken as Ct value > 36 in our laboratory), to be used in deciding the infective potential of the patients, their discharge from the hospital and de-isolation of the patients. This will help in the timely discharge of patients from health-care institutions and home isolation, which, as a result, will lead to optimal utilisation of the limited hospital resources we have available in the line of the ongoing pandemic. Future studies are required to define the exact cut-off of Ct value for de-isolation purposes.

Keywords: Coronavirus; Cycle threshold; Patient discharge; Patient isolation; Reverse transcriptase-polymerase chain reaction.