SINGAPORE — There are no tests for any disease that can be foolproof but the authorities have put in place stringent processes to minimise the possibility of errors, said a senior Ministry of Health (MOH) official on Friday (15 May).
The comments by the MOH director of medical services Kenneth Mak at a multi-ministry taskforce conference were in response to a question by a reporter on the recent COVID-19 false positive tests in Singapore.
Last Sunday, the MOH said it had recently found that 33 confirmed cases of COVID-19 from a laboratory were false positives “due to an apparatus calibration issue for one of its test kits”. The discovery was due to its regular reviews of laboratory tests.
“There are no tests available for any disease, where the test is hundred per cent sensitive or hundred per cent specific. In other words, in every test, there often will be a situation where there may be false errors and this is intrinsic due to the fact that these tests may not be accurate completely,” said Prof Mak.
In certain instances, tests can yield a false positive or false negative rate, and the reasons for each might vary, according to Prof Mak.
A false negative rate may occur due to problems with swab testing. If a specimen is not adequately collected, the test may not detect the presence of the virus and allow for the diagnosis of an infection.
There may also be a laboratory error contributing to a false positive or false negative rate.
In addition, the accuracy and quality of a test may vary and this lends itself to a false positive or false negative rate, Prof Mak explained.
There are several robust processes in place to limit and reduce the error rates, Prof Mak said.
Personnel who are doing the swab testing are properly trained and they undergo competency testing before they are allowed to perform their tasks, Prof Mak said. After training, the personnel may undergo a period of supervision before they are allowed to carry out testing independently.
There is also a quality assurance program aimed at reducing the possibility of errors occurring through the standardisation of processes in the laboratories carrying out the tests. The authorities are continuing to work with the laboratory responsible for the false positives to prevent a recurrence of the incident, Prof Mak said.
In addition, the authorities are looking at whether certain tests could be the reason why error rates may take place. Before any test is introduced in Singapore, it has to be validated locally. Hence, a number of tests have been validated for use while others have been rejected for failing certain standards.
Prof Mak said, “False error rates can be significant because they may lead to a person being wrongly diagnosed to have infection or a person assumed not to have infection but was in fact infectious. Therefore, we aim to keep these rates as low as possible.”
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