KUCHING: The need to revise the current isolation and quarantine days based on the Cycle Threshold (CT) value is not necessary, says Dr Helmy Hazmi, an associate professor with Universiti Malaysia Sarawak’s Faculty of Medicine and Health Sciences.
The public health expert said that isolation and quarantine should be triaged against the incubation period, the peak infectiousness period of the virus, the vaccination level and the need for social and economic recovery.
“This is a really simplistic way of looking at the function of the CT value. Only PCR testing gives out the CT value reading.
“PCR testing is not cheap and results can be slow, especially when cases are at its peak. There can be a bottle neck and mass confusion if we depend on the CT values to decide on the quarantine period.”
He said this when asked by New Sarawak Tribune for comments on Bintulu MP Datuk Seri Tiong King Sing’s suggestion to the Ministry of Health (MoH) that quarantine periods for Covid-19 patients be measured according to the CT value.
Dr Helmy said the CT value should be read with caution as there were many caveats.
“The value is not absolute and its precision is affected by many factors. You may get two different CT values even if the samples were taken from the same person at the same time.
“Some of the factors that affect CT value readings include the specimen collection devices, the technique used, whereby some operators collect the specimen through the nostrils only, as compared to collecting samples from both the throat and through the nostrils, the extraction method and the chemicals used in the PCR methods. Techniques and algorithm can differ from lab to lab.”
He also said that patient’s health condition and vaccine status could also affect the CT values.
“The CT value gives an idea on the viral load in the body. But it cannot be sure to tell if the infection is just starting or ending. Therefore, a person with high CT value (low viral load) can still infect others.
“Hence, for public health point of view, the PCR is better used as a qualitative test, that is, informing us on whether the person is positive or negative. In an outbreak, quick and decisive action is needed to manage the case.”
Dr Helmy said the CT value had more academic value to it because of its quantitative nature.
“When read with other indicators and the patient’s clinical presentations, the serial CT value can be useful to predict the severity of the disease.
“When there are too many close contacts to trace, the CT value can be used to prioritise, by choosing the individual with the lowest CT value (showing high viral loads) indicating that the outbreak is expanding.”
Recently, in his address during the Dewan Rakyat sitting on March 3, Tiong was worried that seven days of quarantine for patients would not be able to stop the spread of infection.
He also said proper and safe quarantine procedure was crucial to control the increasing cases.
