Ministry's measles text explanation prompts questions
The Ministry of Health says the large gap between "suspected" and "confirmed" cases of measles in Samoa is because laboratory testing suspect cases is "not straightforward", but a leading vaccine experts is raising questions about these claims.
At a press conference on Thursday afternoon, Director General Leausa Dr. Take Naseri said of the 716 suspected cases of measles in Samoa, 40 per cent of which have been admitted to hospital, approximately 200 have had specimens sent to Australia for testing.
The Ministry of Health says the gap between "suspected" and "confirmed" cases of measles in Samoa is because of lab testing difficulties, but a leading vaccinologist is casting doubt on those claims.
He said around 70 of those tests have been returned, and 48 of them came back positive for measles, suggesting 22 negative tests and 130 which were not yet returned. Leausa returned blamed the testing process for the long return time:
“Sometimes they need to rerun the specimens [unverified]. Sometimes the specimens are insufficient… [which] sometimes happens because you have to airfreight it," Leausa said.
“It’s not as straightforward as might allude to.
“I think you are trying to find ways to discredit efforts done by the lab.
“They [the laboratory] don’t want to force results, which can cause a false positive. They have to be 100 per cent before they release that.”
University of Auckland Vaccinologist Dr. Helen Petousis-Harris said the measles test is well established and routine, and needs minimal testing material to be completed.
“The test for measles is very sensitive,” she said.
“Normally tests will measure if a person has made an immune response to measles and if there is evidence of the virus: two different kinds of tests. These kinds of tests are generally quite reliable.”
She said delays like the ones Samoa is reporting (tests which occur in Melbourne, Australia) are inconsistent with laboratory results in New Zealand: “It’s inconsistent with other experiences.”
She said at the stage where there is a clearly an epidemic, reliance on testing itself and the distinction between suspected and confirmed cases is less important as patients present with clear symptoms “it becomes more likely that people who look like they have measles do."
“If it looks like a duck and quacks like a duck, it’s probably a duck," she said.
The large disparity between the number of suspected and confirmed cases (716 and 48 to date) mostly stems from the fact that Samoa has not sent every single case sample to be test by the lab, Leausa said.
The Ministry says it takes three weeks for tests results to be reported to Samoa from Australia.
But in American Samoa, where two measles cases were discovered on Sunday, samples sent to Hawaii for testing were expected to be returned within about two days.
Tests took just four days to be returned in Fiji, according to an update filed by that country's Government on November 11.
“We cannot test all 700, it would be very costly. We test only the severe cases of measles,” Leuasa said.
“We sent over 200 specimens.
“Of most of the cases we sent most of them have gone home, there are only a couple of deaths that were confirmed measles.”
Dr. Rasul Baghirov, Samoa’s World Health Organisation representative said because the V.I.D.R.L is a W.H.O. reference laboratory, the testing is done for free.
The prohibitive cost is in the freighting of samples to Australia.
The Director of the laboratory Samoa has been sending specimens to say they are returning tests in a “timely manner".
“The W.H.O. Measles and Rubella Regional Reference Laboratory for the Western Pacific Region at Doherty Institute is providing measles laboratory testing support for Tonga and Samoa to assist with their respective measles outbreaks,” said Dr. Mike Catton, Director of the Victorian Infectious Diseases Reference Laboratory (V.I.D.R.L.) at the Doherty Institute.
He said samples were being returned in a "timely manner". Guidelines state that all results should be reported within a week, and that positive results should be reported in 24 hours.
The 2018 Manual for the Laboratory-based Surveillance of Measles, Rubella, and Congenital Rubella Syndrome states the exact details of reporting timelines should be arranged between the laboratories and the countries requesting the results.
“In general, however, all results from suspected cases should be reported within a short turnaround time (3-7 days) as established by the national or regional guidelines. In the absence of recent cases, a positive result should be reported within 24 hours,” the manual states.