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CONSIDERATION SHOULD BE given to the use of a system of rapid testing for Covid-19 but such antigen tests typically show “reduced diagnostic accuracy” compared with the current test, the Health Information and Quality Authority (Hiqa) has said.
In a review of alternative testing to detect Sars-Cov-2 – the virus that causes Covid-19 – Hiqa said that the introduction of validated rapid testing in Ireland “should now be considered to enhance Covid-19 prevention and control”.
At the request of the National Public Health Emergency Team (NPHET), Hiqa carried out this assessment of alternatives to the current PCR testing used across the country to test for Covid-19.
It comes at a time when significant pressure has been put on the contact tracing system, with in excess of 110,000 tests completed in the last week in Ireland.
It has emerged that the HSE is to ask more than 2,000 people who received a positive Covid-19 test result last week to alert their own close contacts due to “unprecedented pressure”.
The current PCR testing used in Ireland and around the globe is expensive and time-consuming. Numerous forms of rapid tests are either being developed or have been developed – that could take as little as 30 minutes – and opposition TDs such as Labour leader Alan Kelly have called for rapid testing to be introduced here.
In its review, Hiqa said that it would be vital to study how effective rapid antigen detection tests are in an Irish setting to help determine its “real world performance”.
However, given the variation in accuracy across the different forms of tests, it couldn’t give an “across the board” recommendation to adopt rapid testing.
Dr Máirín Ryan, Hiqa’s director of health technology assessment, said: “While testing people at or near the point of care, including with the use of rapid antigen detection tests, has the potential to expand test capacity, reduce test turnaround times and improve access, such tests typically show reduced diagnostic accuracy compared with the current test.
“Therefore, depending on the circumstances, results from a rapid antigen detection test may need to be confirmed with the current rRT-PCR test.”
Dr Ryan said a cohesive national strategy is needed to ensure the right tests are undertaken in the “right people at the right time for the right purpose”.
“Planning now to support delivery of the strategy will facilitate rapid deployment of tests that meet the requisite standards once validated for use,” she added.
Hiqa submitted the findings of its health technology assessment to NPHET earlier this month.
There are already huge doubts over the amount of amplification cycles being used by the HSE which may result in false positives. I have a feeling that in years to come, we will see the HSE’s handling of this to be as inept as one would expect given their history.
@Ned Gerblansky: seal the files for 30yrs+
That will get them off
@Ned Gerblansky: Cilliam de Gascun confirmed on 13th September on his Twitter account that the threshold cycle is 35-45. Anything over 33 is not recommended. He said that NPHET have not decided on the threshold cycle but that it is determined by the manufacturer of the test kits. He also said if we develop our own in-house test kits that cycle threshold could be reevaluated.
@Anna Anna: in Taiwan they don’t consider any pcr test cycle over 35 as a positive as it’s only the dregs of old rna your getting. Over 32 cycles it’s not contagious or infectious but we are doing the cycles here between 35-45 cycles so no wonder we are getting loads of positives tests and nobody is sick the hospitals would be full otherwise
@Arsebiscuits: yes, and I read this week Wuhan are only counting positive swabs as cases if there are symptoms present also
@Arsebiscuits: Published in The Lancet 3 weeks ago https://www.thelancet.com/journals/lanres/article/PIIS2213-2600%2820%2930453-7/fulltext
@Anne Marie Devlin: yes the Lancet paper estimates the UK false positive rate to be 0.8 – 4%. That figure is calculated from the number of tests carried out, not the number of actual positives in the week. So if they are testing 100000 people per week and 5000 tests came back as positive that means there could be as little as 800 false positives (0.8% of 100k) in that 5000 figure but the false positives could be as high as 4000 (4% of 100k). Cillian de Gascun said our false positive rate is 1-3% on 13th September.
@Ned Gerblansky: “There are already huge doubts over the amount of amplification cycles being used by the HSE which may result in false positives.”
Wrong, misinformation!
There are protocols in place to prevent False Positives in the case of Weak Positive results, that a liable to give a false positive. If a test is Weak Positive on the first test and the original sample cannot be retested to check its validity, they will called back a person be tested again a week later.
Only if they return a Strong Positive result on the 2nd test or develop COVID-19 symptoms at the time of the 2nd test, are they counted as True Positive result.
Weak positive results are not counted as True Positive, this lowers the risk of False Positives.
However, we learnt yesterday that only 50% of people are turning up for their 2nd test, so many weak positive results are not followed up, some cases remain undiagnosed and weak positives are disregarded.
https://www.thejournal.ie/covid-19-testing-half-close-contacts-second-test-5239242-Oct2020/
See: Proposal for the management of weak positive (high Ct value) PCR results in the setting of mass testing of asymptomatic individuals for SARS-CoV-2
@Anna Anna: “Cillian de Gascun said our false positive rate is 1-3% on 13th September.”
However, we have protocols in place for handling Weak Positive results (>34 amplification cycles), which decreases the risk of False Positives.
We retest the original sample, preferably on a different machine, if it comes back positive a 2nd time, it is treated as a true positive.
However, if an original sample is not available for retesting, as is most often the case, a person will be called back for a 2nd test a week later. If they test Strong Positive i.e. positive after <34 Amplification Cycles (viral number rising) and/or develop symptoms of COVID-19 and test positive, they are counted as a True Positive.
However, we learnt yesterday that 50% of people (often the traced contacts of infectious cases) are not turning up for their second test. So many weak positive results are not followed up and are disregarded.
The positivity rate among contacts, on the first test, 7 days after exposure, is is 2-3% (only Strong Positives are counted as True Positives on the first test).
So all in all, the protocols in place, distinguishing between Strong Positives and Weak Positives, and retesting Weak Positives, lessen the risk of False Positives among Weak Positive results.
References:
Proposal for the management of weak positive (high Ct value) PCR results in the setting of mass testing of asymptomatic individuals for SARS-CoV-2 https://www.hpsc.ie/a-z/respiratory/coronavirus/novelcoronavirus/guidance/outbreakmanagementguidance/PCR%20weak%20results%20guidance.pdf
and
https://www.thejournal.ie/covid-19-testing-half-close-contacts-second-test-5239242-Oct2020/
@David Jordan: All the armchair medical scientists out there hey? I shouldn’t have bothered doing five years in college when people can just google Ct thresholds and multi component plots….
@Anna Anna: Yes in Wuhan they only count you as a positive if you’ve got symptoms. They tested 10 million people in Wuhan over the summer and concluded that asymptomatic people do not spread Covid 19. They tested toothbrushes, phones, door handles etc that asymptomatic people came into contact with and found zero cases of Covid 19. In Ireland we count every person and base our restrictions on that. Also if People who don’t have symptoms stopped getting tested it would stop all this once and for all. Refuse a test if you’ve no symptoms and then we’d see the real figures
@David Jordan: Wrong! Misinformation! Weak positives cannot just be disregarded (for obvious reasons) if the person does not show up for the second test. As you also note 50% of people do not show up for this. There would be many denominations if they were disregarded.
- As noted in the European Journal of Clinical of Clinical Microbiology and Infectious Diseases positives with a cycle threshold over 33/34 are not contagious and can be discharged from hospital care or strict confinement. End of the day our cycle threshold should not be more than 33/34. With a cycle threshold of 35-45 you are just creating a lot of hysteria
@David Garland: “Yes in Wuhan they only count you as a positive if you’ve got symptoms.”
China was criticised for not acknowledging that asymptomatic cases existed and are infectious. By hiding the fact that asymptomatic cases did not exist, they could claim that fewer people were infected and they were doing better then they really were. Typical dictatorship.
The WHO says acknowledges that are studies that find that 40% of infections are caused by asymptomatic cases.
” WHO clarifies stance on the asymptomatic spread of coronavirus It’s not as rare as a misunderstanding on Monday led people to believe.”
“But by Tuesday Van Kerkhove said there had been “misunderstandings” regarding her Monday statement and clarified that what she was referring to as “very rare” was a subset of studies, not asymptomatic transmission globally. She also added, “Some estimates of around 40% of transmission may be due to asymptomatic, but those are from models, and so I didn’t include that in my answer yesterday but wanted to make sure that I covered that here.”"4
40% of transmission may be due to asymptomatic cases.
@David Jordan:
I’m not sure that the Journal article supports your argument David.
You seem to be suggesting that all weak positives are re-tested, but the Journal article only refers to people tested as close contacts of a confirmed case.
Until I read your comment, I was not aware of any distinction between the relative strengths of positive tests. The clear understanding has always been that every positive test is included in the daily numbers. Does NPHET and the HSE maintain separate records or statistics of positive tests that are discarded and not included in the daily numbers?
Your second link is to a very recent update to a proposal document.
It’s not clear if it has been adopted and is now active policy.
Also, point 9 of the appendix seems to reinforce the comment made by Ned.
@Anna Anna: ***denotifications
@Ned Gerblansky: I’m all for clarity but every country can’t be doing the tests wrong, what’s the cause for the spikes across all of Europe?
@David Jordan: unfortunately what you have presented does not conflict with my initial statement. The number of admission cycles brings us in to false positive territory. Also you use of the word “our” suggests you work for the HSE. If this is the case, please get back to work, you have more important things to be doing than dredging through comments.
@Martin: I’m not insinuating this is responsible for the spike at all. In fact, this is a small proportion of cases. Covid is still rampant
@Anna Anna: “Wrong! Misinformation! Weak positives cannot just be disregarded (for obvious reasons) if the person does not show up for the second test.”
No.
As explained in the document I sent you, there are protocols in place that reduce the risk of false positives at high amplification values (Ct value >30), I am sorry if this is not what you want to believe.
Specimens are retested, if available:
“For all specimens positive with a high Ct value (generally more than 30 but this will be assay/platform dependent) the original sample should first be retested. Retesting of the sample should ideally be performed on a second assay platform, but can be on the same platform if an alternative is not available”
If the person has a prior history of infection, find out if it is residual virus from the person’s earlier illness, Ct value will fall by the 1st test:
“If the individual being tested has a prior history of confirmed SARS-CoV-2 infection, compare the Ct value from the time of their infection with the present Ct value.”
Seems they might want to know if they are a rare case of re-infection
Weak Positives are not counted:
“If there has been no change, or a significant increase in the Ct value (i.e. a decline in the viral load), and the individual remains asymptomatic, then this is likely to reflect residual non-infectious RNA and no further action is required. The result does not need to be notified to public health”
Weak Positives are not counted:
“If no features of COVID-19 develop within the 7 days and the repeat test still has a high Ct value or SARS CoV2 RNA is “not detected” the possibility of early pre-symptomatic infection with rising RNA level can be discounted. If there is no other indication for isolation/transmission-based precautions these can be discontinued at that time.”
@David Jordan: as you said yourself David in the previous comment ‘if an original sample is not available for testing, as is most often the case the person will be called for a second test’. 50% of people, as we know, do not show up for their second test. So those 50% continue to be regarded as positives. It is obviously negligence to disregard those positives without a second test or a retesting of the original sample (which you say in your comment is rarely possible) so they continue to be included in the confirmed cases number.
@David Jordan: arguments about the pcr test’s accuracy are somewhat missing the point in current circumstances. People can throw studies back and forth at each other to support their argument.
What is not in question, however, is the upward trend in covid-related hospitalisations, ICU admissions, and deaths.
@Anna Anna: the more serious negligence is if these people do not self-isolate
The testing process that is being used is flawed and unreliable anyway, so how much of a difference is there between the two.
@Garry Coll: from what I have seen on a harvard paper. The current test runs at about 2-27% false positive higher rate of failure with highernumberson cycles. The next best is 50%false positive at best.
Rapid testing for all ports . I know it wont catch everyone but it will catch a good proportion, gotta start somewhere.. So many empty hotels now get a few for isolating only people who arrive with high temp..
But it has also been said that the pcr test is over sensitive and picks up dead virus as being live.
Oh my God. “, given the variation in accuracy across the different forms of tests, it couldn’t give an “across the board” recommendation to adopt rapid testing”. Tell them which ones are best. FFS
Is this the same rapid test they are already successfully using in China and the US ? What’s the delay in introducing it here ?
@Alan: Its like the masks, make up excuses until stocks can be got hold of then big uturn..
@Alan: The answer to your question is right there in the headline. The article itself goes into more detail. False positive tests are a huge inconvenience to those that get them and a trigger for the conspiryloons to start spreading nonsense. But other than that they are fairly inconsequential. A false negative however, which with even the current tests are just as likely as a false positive, can have potentially deadly consequences. The authorities have to weigh up the pros and cons involved. Faster results and potentially lower accuracy vs slower results and higher accuracy. No test, either for Covid or anything else, is 100% accurate. So when it comes to deciding which tests to use a median has to be found between accuracy and speed, something of particular importance when it comes to infectious disease.
I flew out to Maldives on Monday. Had to get a PCR test and negative certificate from Tropical Medical Bureau for €180 to enter Maldives. Best decision i made was to travel. Found it very safe on Qatar Airways. Facemask and visor worn for duration of flight. Here in Maldives it’s 32C all al fresco dining. All staff had to quarantine for 14 days when they came back to work and were tested every 2 days for duration of quarantine period.
How our government has not come up with a similar solution to boost tourism is beyond me.
#safetourism
@BRIAN MCCARTHY: you do know our government don’t you!!. A Taoiseach that found out about the contact tracing debacle in a text from Irish Times reporter. A Tanaiste who didn’t even know which midnight lockdown was starting. Thats what we are up against a virus and a pathetic excuse for leadership. Saving the economy is not even on their radar.
This article will definitely trigger our mob of “experts” who recently graduated with first-class honours from the University of Conpiracyland. Almost every country in Europe, and many more beyond, are reporting increasing cases, increasing hospitalisations and increasing deaths, but these reports can’t be true if our resident “experts” are correct. Either our “experts” are wrong or the overwhelming majority of actual experts in the world are wrong. Sorry conspiryloons, but I know who I’m putting my money on.
Quick test at Heathrow now £80 … 20 mins .. would that be a waste of money .. it’s quite reasonable to be fair .
@Terry Cahill: It would make sense as that would deter people from travelling and transmitting the virus if there’s an extra cost to their journey. I know travel cases for the transmittance of the virus is low but it literally started from 1 person arriving here back when it initially broke out here in Jan/Feb!
How about use the test recommended by the WHO ffs?
They’re having a think about changing the test. Maybe. https://www.hpsc.ie/a-z/respiratory/coronavirus/novelcoronavirus/guidance/outbreakmanagementguidance/PCR%20weak%20results%20guidance.pdf
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