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SINGAPORE: Other laboratories are not using the same COVID-19 test kit and combination of analytical instruments as a laboratory that had 33 cases of “false positives,” said the Ministry of Health (MOH).
Thirty-three previously confirmed cases of COVID-19, including a radiographer working at the Singapore Expo Community Care Center, turned out to be negative cases after further testing by the National Public Health Laboratory.
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This was due to a “device calibration problem” for one of the test kits used between May 5 and 9, the Health Ministry said Wednesday (May 13) in response to CNA’s questions.
“The Ministry of Health has since reviewed the test results of the affected lots, and no false negative results of the review were discovered,” the health ministry added.
READ: COVID-19: 33 cases found as ‘false positives’ including health worker at Singapore Expo community care center
None of the other 12 laboratories that perform COVID-19 tests are using the same test kit and combination of analytical instruments, MOH told CNA.
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“The laboratory has switched to another test kit that has been shown to work on the analytical instrument,” said the health ministry.
The 33 cases had been isolated after “they were supposed to have COVID-19,” and will “undergo additional testing as needed,” the MS added.
A large majority of COVID-19 tests in Singapore are carried out by the National Laboratory of Public Health and acute public hospitals, with the support of several private laboratories, the ministry said.
“The MS regularly audits the test results from these labs. The results of the laboratory tests are also compared with the clinical signs and symptoms of the patients, “he said.
READ: The public “should not be too alarmed” by the large number of cases of COVID-19: Minister of Human Resources
WRONG RESULTS
The Ministry of Health also reported Sunday that two people from the public health sector working at the Singapore Expo community care center, cases 18669 and 19360, had “misleading” results.
Their results were also sent to the National Public Health Laboratory for retesting, and they yielded negative results.
MOH told CNA that the equivocal results “occur from time to time.”
“The labs also have a workflow to verify equivocal results, including repeating the tests with another comparable test kit, if available, and requesting that a new sample be collected,” the ministry explained.
“If the problem cannot be resolved in the end, the samples are sent to the National Public Health Laboratory for confirmation.”
As a precautionary measure, public health measures, such as contact tracing, can be introduced for cases with equivocal results while awaiting verification, the health ministry said. These patients will also be isolated.
READ: Singapore’s COVID-19 cases exceed 25,000; new daily maximum of 958 discharged patients
LOW TEST CAPACITY
Singapore had to reduce its COVID-19 testing capacity due to the problem in the laboratory that resulted in 33 cases of false positives, Health Ministry director of medical services Kenneth Mak said Tuesday.
Authorities are giving the laboratory time to properly recalibrate and revalidate its test kits, as well as to work through its “quality assurance processes,” added Professor Assoc Mak.
“We lowered our testing capacity accordingly to give them some room to work on these processes. We anticipate that this should complete very quickly, and then we should be able to return to our current full testing capacity. This may occur in the coming days, “he said.
Singapore was conducting 7,500 to 7,600 COVID-19 tests a day before the problem was detected in the laboratory.
“The results that emerged from that particular set of tests performed were not correctly interpreted,” he added.
“There were also some steps that were not completed, followed. If those steps had been followed completely, perhaps we could have chosen some of these outcomes a little earlier.
“We are working with the laboratory to complete this quality assurance process.”
READ: COVID-19: Singapore Registers More Discharged Cases Than New Patients in One Day
To avoid having incorrect results in the future, the Ministry of Health has put together advice and recommendations for all laboratories involved in the tests.
These warnings describe the standard processes they have to perform to ensure that tests are performed correctly and that accurate tests are produced, Professor Assoc Mak said.
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