HOW COVID-19 TESTING AFFECTS OUR DECLINING POSITIVE CASES - BFM interview (9 Jun 2021)

 

With our daily Covid-19 positive cases declining in the past few days, experts have pointed out that testing efforts are also decreasing. We speak to Dr Lim Chee Han to understand this relationship and the importance of testing in our battle against Covid-19.

Produced by: Kelvin Yee

Presented by: Lee Chwi Lynn, Sharmilla Ganesan

Link is here

1. Talk to us about the relationship between the daily case numbers and the number of tests conducted.    

 

Ok, The public’s general logic is that, once we reduce the number of tests conducted,consequently we should expect a lower daily case number, or another way round if we increase a lot more tests, we should expect a higher number of positive cases.   

My observation and analysis based on these two sets of numbers from 1st May up to 8 June yesterday, the result shows that there is a non-significant weak correlation: about 50% of cases you can observe are true about the public perception: the daily case numbers do follow the test number. In other words, another half of the time you could get it wrong if you bet on that to happen.

 

 

2. How does testing aid our fight against the pandemic?

 Testing is absolutely fundamental for disease control management, contact tracing and surveillance purposes. We need to know who needs to be quarantined or isolated , who needs to be put under early treatment , who else we need to contact for tracing where the viruses disseminate. The test results would give the health authority a certainty in deciding the next course of action on how to deal with the Persons under investigation (PUI) and Persons under surveillance (PUS). The government needs that information to manage the spaces for our hospital beds and many quarantine centres as well.

So, it is crucial that we have enough testing capacity and actually test enough for the disease control purpose.

 

3. Why is it important to get an accurate picture when it comes to the case numbers here?

 It is important for the government and our society to know how many are detected positive, so that they could be quarantined away and be treated early for any sign of worsening symptoms. This can prevent the infected persons from going on to cause more disease transmission in the community, as well as saving the persons from severe illness and death.

 

4. What determines our testing numbers? What are some factors that might explain why it drops or rises?

 To answer the question (about what determines the testing numbers), we should understand the circumstances for testing: first, if you are a close contact to a confirmed positive case, a health district officer would ask you to come forward to get the testing done by them. This is via contact tracing effort. Also there are circumstances where one is compelled to do covid testing, such as at the border when arriving from overseas, before surgery operations or emergency procedures and so on. Health officers also may go out and do surveillance testing in the targeted community. These are regular works for the government, probably what is affecting their work rate and output is the number of staff on duty during the weekends and public holidays.

But we also need to look at the contribution from the private labs. Besides the tests which are outsourced by the government, the general public can also voluntarily go use the private covid testing services if one is not categorised as close contact but has high suspicion or concern that himself/herself is infected. In addition, covid-testing campaigns run by the state government or elected representatives could also push up the test number.

The contribution from the private labs is not low: the breakdown data given by the Director General of Health Noor Hisham on 20 May shows that slightly more than half of the total RT-PCR tests came from the private labs. The data also show that private labs command 72% of the testing capacity of the country but that day they only used one-third.

Now I come to offer my explanation about the testing number trend -- one needs to appreciate that the Health Ministry has a cut off time for COVID-19 status daily reporting at 12noon, so whatever numbers finally presented are actually reflecting the situation yesterday’s half day and today’s half day.

From what i can see from 1st of May until yesterday, the weekends and public holidays effect is pretty strong and highly correlated: typically, if you compared the Sunday’s status report to the Saturday’s test number, For example, 6 Jun last sunday we saw a 13.3% reduction compared to preceding day, 30th May we saw a 13.4% reduction in test number. And usually we can also observe further reduction reported on Monday’s status briefing report reflecting on Sunday’s outputs. The only exception to the case is during the Raya Holiday, the significant dip was reported mid-week,( and some went back to work during the weekend.)

Why the weekend effect? If you go check the working hours of the service provided by private labs, most only do half day during the weekend and public holiday, hence you could expect significantly fewer samples contributed from the private labs. Just today the Director General of Health Noor Hisham released a short statement, pointing out that non-health ministry labs may sometimes report the negative test results late, especially during holidays, resulting in lower test numbers.

 

5. And what determines the speed at which those tests are processed?

Procedure-wise, RTK test can give us a very quick result, say the result to be produced in half an hour; for RT-PCR test, if one takes the sample and goes into the lab to perform directly , you should expect the result to be out in 3 hours. But, you know, when things are performed on a large scale and have to organised systematically, that could take a bit longer, but still should be done within 2 hours for RTK and one day for RT-PCR. The result has to be verified and signed off by a pathologist in the health ministry or relevant doctor in the private setting. So, from sample taking, to running the lab procedure to verification and documentation, until reporting to the system and the tested person, one should appreciate it will take some reasonable time for these procedures.

 

6. How much testing is enough?

6a) What are some benchmarks we should be following and achieving?

 

This is a tough question, I don’t think anyone could say that they have a correct answer (on how much testing is enough).

On the benchmark, the statement from our DG Health Noor Hisham today reiterates that WHO set the benchmark of sufficient testing if one positive case is accompanied by at least 10 negative cases and at best 30 negative cases. Currently we pass the minimum threshold but not yet at the best optimum level.

For the disease control purpose, I would argue that the health authority should order as many as reasonable and timely for contact tracing and high risk area surveillance.

But If one’s aim is to catch all asymptomatic cases throughout the country, then how much testing is enough one needs to ask how much is operationally possible for the government and the whole society to pool together to do the mass testing. The limits are the testing accuracy, manpower to perform the sampling and delivery, as well as laboratory testing capacity.

But how often the testing should be done, can the government healthcare facility and workforce cope with the surge of cases? -- one should not think just about the testing, what is more important is the contact tracing work and treatment follow up with the confirmed patients. It will be totally irresponsible if one is tested positive and no one could follow up - I guess you can imagine that.

 

 

7. How can we increase testing?

7a) With public health infrastructure being strained, how can tests done using private services be made more affordable?

 

For your information, at times the government is also outsourcing to the private facilities for testing, since the private labs have the most and significant capacity for testing. I would personally urge the government to do more testing for contact tracing if it is possible to arrange, and do more testing in targeted high risk community surveillance. That should be the direction of increase testing. I hope the government can negotiate better and more affordable deals, at the same time hope the private market competition could drive down the service pricing too for the general public.

Recently there is a RTK product which can be easily used at home, one can just test the kit with your own saliva. Maybe these kind of self-testing can be helpful.

 

8. Have you seen any signs of an exit strategy out of this current MCO?

The current MCO looks like preventing the rising trend of daily new cases in the past few days, though the disease burden in the community is still high at the moment. If the economic sectors and various social sectors have to be open in the near future, if SOP could only be effective to a certain extent, then we need to vaccinate the whole population as soon as possible to achieve herd immunity. Once we pass the 50% mark of the vaccinated population, we can expect the disease transmission to go down and control much easier.