Challenges associated with using cycle threshold (Ct) value of reverse-transcription polymerase chain reaction (RT-PCR) as a criteria for infectiousness of coronavirus disease 2019 (COVID-19) patients in India

There may be a difference between the amount of virus collected and the amount of virus present within the nasopharynx of an individual, which is dependent largely on the swab collector. [...]they recommend that these variations be corrected with markers that should be integrated with commercial tests to standardize results.6 Notably, different laboratories have implemented different Ct value thresholds at which a negative test is declared. According to the state government of Maharashtra, certain laboratories were using a Ct value of 24, and any higher value was declared negative.7 These assessments created a dangerous situation because the patients with Ct values between 24 and 35, who would otherwise test positive, escaped further follow-up. [...]this population skipped the 14-day quarantine period for COVID-19–positive patients and moved through the public as unknown carriers of the virus, leading to further spread. [...]the Ct value is an important tool that can be used to aid contact tracing and isolation.