Why are the 98,289 positive COVID-19 cases via serology tests not included in total tally?

On Monday (14 December), the Ministry of Health said in a statement that 152,794 migrant workers living in dormitories have had the COVID-19 virus or about 47 per cent of all migrant workers.This may seem like a huge spike from the over 50,000 number of positive cases that we were aware of.That’s because this new figure includes 54,505 migrant workers who tested positive from a polymerase chain reaction (PCR) test as well as the 98,289 who tested positive via a serology test only, which is used to detect if a person had been infected in the past.The figure of 54,505 has been public knowledge. This is the number that has been updated day to day by the MOH as it continues to track and trace and report on the COVID-19 situation in the country.The second figure of 98,289, however, was only recently released by the MOH. The ministry also stated that another 65,000 serology tests are still being carried out.“This will give us the full picture of the infection prevalence among our migrant workers,” they said.The question here, then, is: Why was the number of positive serology tests not made public until now?The MOH started mass testing of migrant workers in dormitories for the virus back in May.Citing a study of workers in purpose-built dorms who tested positive on 25 July, the ministries noted that the vast majority of migrant workers in dorms who tested positive from the PCR or serology test were asymptomatic or had very mild symptoms.According to diagnostic guidelines by the World Health Organisation (WHO), a confirmed case of COVID-19 is when:

• a person is tested positive on a Nucleic Acid Amplification Test—such as the PCR used in Singapore
• a person is tested positive on an antigen rapid diagnostic test AND meets the case definition for probable or suspected cases
• an asymptomatic person who tested positive on an antigen rapid diagnostic test who is a contact of a probable or confirmed case

The WHO diagnostic guidelines also stated: "Serology should not be used as a standalone diagnostic to identify acute cases in clinical care or for contact tracing purposes."Essentially, a positive serology test has to be considered with other factors such as the timing of the disease clinical morbidity and prevalence of the virus within the setting the patient is in before it is classified as a case of COVID-19.So the other question here is: Why was the figure of the serology tests conducted on migrant workers not included in the total number of cases which still stand at around 58,386 at the time of writing?After all, the serology test shows that these workers have been infected with COVID-19 at some point in the past, even though they are currently free from the virus. We also know that over 54,000 migrant workers have tested positive for the virus via PCR tests.We also know the dorms are cramped and many of these workers are mingling with each other on a regular basis.So the total number of positive cases for migrant workers living in dormitories should be 152,794, inclusive of those who tested positive on the serology test.

Isolation inconsistencies of migrant workers who tested positive

Back in August, the MOH said that the entire migrant worker population has been tested at least once, either via the PCR or serology tests. It explained that workers who tested positive were isolated, including those who were found to have been infected in the past but are not anymore, and that all workers are being given medical care.In an earlier report in July, TOC highlighted the story of an employer who learned that two of his workers were sent back to their rooms in Toh Guan Dormitory after being tested positive for the virus. This is opposed to being moved to an isolation facility as they should have been.After some back and forth with the MOH—and an apology from the dorm operator on behalf of the MOH—the two workers were finally sent to recovery facilities.Another case involved a worker who tested positive being placed in the same room as 11 other healthy workers by the dorm operator for two days instead of being immediately transferred to an isolation facility.The employer said in a Facebook post that she was told the MOH needed another 24-hours to make relocation arrangements. But 48 hours later, the workers still hadn’t been relocated. In the meantime, the dorm operator said they couldn’t do anything about the situation and asked that the healthy workers in the same room wear masks.Now, these are just two examples of such incidents where COVID-19 positive migrant workers were being sent back to their dorms, mingling with uninfected workers, instead of being immediately isolated.TOC had spoken to a few other employers as well with similar stories by they declined to share it publicly for fear of repercussions from various ministries.Coupled with the previous reports on the cramped conditions at many of these dormitories and these cases of migrant workers mingling with each other despite their COVID-19 results, it’s not surprising to expect that a majority of migrant workers in dorms will end up catching the virus.