Assoc Prof Jamus Jerome Lim asked the Minister for Health whether the protocol that disregards active polymerase chain reaction test results for recovered COVID-19 individuals, as long as their cycle threshold (CT) values are sufficiently high, is also applied to newly-detected (and especially asymptomatic) cases which may be at the beginning or tail end of their infection.

Mr Ong Ye Kung:  The cycle threshold (CT) value indicates the viral load of the patient being tested. However, unlike internal body scans or blood tests which are clinical tests with reported results, a CT value is technical laboratory parameter, with calibrated cut-offs for positive results, that is not routinely reported to patients. 

 Doctors can disclose the CT values and discuss its clinical significance with patients. In most situations, the CT values do not affect the clinical management of a COVID-19 positive case. The risk profile and severity of symptoms of the patient are more important. 

A recovered patient and a newly-infected person may both test positive and register high CT values, i.e. low viral -load, but the interpretation is entirely different, and needs to take into account the clinical context. For a recovered patient, it is most likely that he is still shedding small amounts of dead viral fragments. For a newly-infected person, it is most likely that his infection has been detected early, and the viral load is likely to increase in a few days, when he will become more infectious. Hence, the clinical management in these two scenarios cannot be similar just because the patients register a similar CT value. 

Ministry of Health
10 January 2022

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