• Kristal
    5
    Hi all,

    I know a lot of businesses are taking up the use of RAT as a surveilance and control process.
    For some time now we have had access to the tests (near sold my soul to get them - but that is another story for another time).

    We recently had a worker with a confirmed Positive PCR, No obvious symptoms (those we are warned about) so have decided to test the RATS (three different approved products in NZ). Everyone of these is coming back Negative - I have now asked the worker to test daily with all three products and are still getting the same Negative result. Subsequently I have asked them to present again for another PCR and am awaiting these results.

    Has anyone else had any similar results - is anyone else testing these out for effectiveness?

    Concerned that this strategy that is being pushed out for the safe return to work may not be as effective as I had hoped. Keen to see if others have any insight or experience with similar findings.
  • Yonny Yeung
    11

    Hi Kristal, upon tested positive PCR, they should be stood down and self isolate, until the next PCR test shows negative.

    RATs are much less sensitive, so not surprised this is the case. There were also concerns that nasal RATs don't pick up Omicron as effective as PCR or saliva test.

    If you need RATs, there are companies offering them around $230 /20pk. BusinessNZ was offering half that price, but preordering is now closed.
  • robyn moses
    62
    Interesting will have to get some positive cases to have a go. We have RATs we have purchased and those distributed through the distribution center (3 different types) to close contact critical workers who are exempt from isolation during work hours. We are relying on the RATS to indicate with some certainty when the household close contacts in particular are positive. If daily RAT test is positive, we do a 2nd to confirm. We have not yet had a negative result after a positive of 20 positive cases.

    Note MOH states after 10 days isolation a positive case may test positive, but this is to be expected and not of a concern as outside of infectious period. Will give them a RAT test when back at work to gauge this
  • Jane
    92
    For a RAT to work and produce a positive, you need the person to be pumping out the spike protein at the site where you swab.
    If a) there is little spike protein being produced (due to the course of infection or the way the person's immune system is functioning right then) or b) there is little snot to carry the spike protein to the swab to the buffer to the well in the testkit - you may not get a positive result.
    This the nature of these tests, and the reason why they will produce false negative tests, and the reason why they have been less useful in NZ's pandemic response due to the low amount of circulating virus in the community until now.
    https://www.monocent.com/wp-content/uploads/2020/10/Web-Covid-gradph.png

    Edited to add, when you see the package insert saying detects 98.6% of cases, or whatever, this will often be with testing people who have a high viral load, and are infectious, and are symptomatic (ie snotty). You can burn through a lot of tests when you test people without symptoms, as they are more likely to test negative with RATs (but may be positive with PCR). But in saying that, it is the people with high viral load and symptomatic who are most likely to spread it to the rest of your team and these are the ones you find with RATs.
  • MattD2
    339
    b) there is little snot to carry the spike protein to the swab to the buffer to the well in the testkitJane
    Also add to this is that it can depend on if the RAT is being swabbed effectively - e.g. are they sticking the swab far enough up their nostril and wiping enough? Can be more likelihood for poor technique when the test is self-administered.
  • Kristal
    5
    Update - Negative PCR received today! Mind boggles a little more.

    Please note this person has been in isolation since CC was established - I have utilised this opportunity to test the effectiveness of the RATs that we have to detect and ensure they are operating the way in which we would expect. Note as of 11:59 tonight this is the primary strategy of our Government in NZ to identify the virus in workplaces and communities - have to say as a H&S practicioner I am feeling less convinced (the information above regarding the Spike Protein is very useful, and I will put consideration into the 'collection training' that has been established to see if this can be improved).

    Unfortunately this Negative PCR has raised more questions than answers and we may have had a false positive PCR to begin with - or - the individual has an iron clad immune system - Either way the timeline makes no sense

    Some background on the individual, M, Heavy set, Active smoker, 45-55yrs, Dbl vax + booster

    Timeline for interest purpose:
    • Exposure to Positive Case (11th Feb - 13th Feb) The 13th being the last day they were with this person.
    • 14th Feb - PC advised individual of their positive result and CC established.
    • Individual - Negative PCR 16th Feb (RA testing daily post CC)
    • Individual - Positive PCR 19th Feb (RA testing daily)
    • Individual - Negative PCR 23rd Feb (Still RA testing)
  • Jane
    92
    Diagnostic testing is a mixture of art and science, and intepreting results is best left to the doctors. There is a lot of grey area when it comes to test results that most people aren't comfortable with, most people like a pos to be actually pos and a neg to be actually neg, but when dealing with people, medical complexities and biochemistry, life often isn't like that.
    There is such a thing as a weak positive that may have been identified by the lab, but it is unlikely that you would get this info. Note too that at the moment there can be up to a 7 day delay between testing and the PCR result being confirmed. PCR can pick up historical cases whereas RATs only pick up active infections.

    RATs have been designed to be as robust as possible, and they have been extremely well tested, and Medsafe have gone over all the data. If your people are following the instructions correctly, and reporting the results correctly, that is all the business is responsible for. There honestly is no need to burn through your precious and expensive tests to decide if it meets standard. They are hardly doing that in the Emergency Department, so you don't need to either.

    Deciding if this person is a covid case, and needs to isolate or not, is not the job of the business. Best leave that to the health system, they have protocols to work to. Your person above is presumably in the medical system in order to have had three PCR tests already, so that is good, and they will presumably let you know if RAT testing is useful from here.
  • Steve H
    308
    RATs have been designed to be as robust as possible, and they have been extremely well tested, and Medsafe have gone over all the data. If your people are following the instructions correctly, and reporting the results correctly, that is all the business is responsible for. There honestly is no need to burn through your precious and expensive tests to decide if it meets standard. They are hardly doing that in the Emergency Department, so you don't need to either.

    Deciding if this person is a covid case, and needs to isolate or not, is not the job of the business. Best leave that to the health system, they have protocols to work to. Your person above is presumably in the medical system in order to have had three PCR tests already, so that is good, and they will presumably let you know if RAT testing is useful from here.
    Jane

    Excellent advice Jane :up:
  • Jane
    92
    To be honest, if I was "M, Heavy set, Active smoker, 45-55yrs, Dbl vax + booster" I would be telling my employer to F off and I would be using my self isolation to find another job.
    Being a close contact is hard enough, without being a participant in a trial of RATs for my employer. H&S is all about the people and making things better, not making things harder.
  • Steve H
    308
    Like your style :grin:
  • Andrew
    405
    A word of caution on RAT's. Don't just read the efficacy on the label.

    The RAT we have pre-orderd had a stated success rate of 97.5% positives and 100% negatives. Amazing I thought - this is super accurate! Maybe too good to be true.

    Interestingly (or not) the packaging didn't give a clear citation of where they got their data from. But with a bit of digging I found that the trial group had 98% of the positive participants had mild to severe symptoms. So it seems the test is very good at picking up covid with those who are symptomatic.

    But I dug further and looked for more independent data on evaluation trials published in medical journals and the like. You know the stuff - something that might be valid and reliable. Not just marketing fluff

    To my surprise one evaluation found that out of 170 PCR negative people the RAT returned 40 positives.

    Now we are in whatever new phase the govt has concocted today we are obviously at risk of closing our workforce down if we mass screen non-symptomatic people on a regular basis. If you have 170 staff you have a risk of sending 40 perfectly healthy people, and their families into self isolation for 10 days. And what happens when you run the tests next time. Another 40 healthy people gone. In a couple of weeks you may have literally no workers left.

    Before implementing routine mass "without cause" screening, I suggest you hunt out independent evaluations of the RAT you plan on using

    The next issue I am trying to get my head around is who pays for this absence. If the person is for all intents healthy, willing and able to work they can't take sick leave. If we as the employer have instructed them to stay away from work it seems we are likely to be the ones liable to pay for the absence. So its money out the door for no productivity. I'll come back on this one.
  • Cam Smailes
    5
    As a COVID-19 positive patient (at home) I can confirm first hand that I had been receiving those negative RAT results when symptomatic until around day 4. With a mild scratchy throat, I conducted RAT's on Day 1 then Day 3 receiving negatives which seems to be in line with what many workplaces are seeing. Went into work the next day thinking the throat was just a casual chill and was not contemplating anymore testing. But thanks to regular temperature checks, on arrival to work I found an slightly elevated temp from normal (we check everyday), conducted a third RAT and voila a positive result. I have since heard of similar symptoms across other workplaces where they are also receiving some negatives, some positives but treating symptoms as likely positives and staying home. Headache and a dry/scratchy throat is a very common symptom from the start FYI and the non contact thermometer was a winner here for sure.
  • robyn moses
    62
    whose paying?? For any of it! The HR of the Workplace where I work with 500 put out the companies isolation payment procedure just last week. I really love that anyone with flu like symptoms is encouraged to stay home and will be paid leave entitlements incl leave in advance as needed. On return to work the employer will apply for the govt. grant and on receipt of payment the leave used to the value of will be reversed. However I, with my HS hat check govt updates daily and see procedure for subsidy requires persons in isolation to have received a confirmation text from the same ph. number that vaccine reminders are sent from and that as of now you are only going to receive such a text if you go through all the hoops to self identify, never mind that not everyone has ready internet access or is internet savey, our workers certainly are not. I have entered 20 self identifications to date and only one entered on the 15 Feb. received her txt from MOH yesterday and a ph. call from WINZ re: subsidy lol...Re: registering as a critical business ect I drove past like 1000 car in the cue for test at Orchard Rd,CHCH yesterday to pick up first set of RATs all they required is me to tell them the order number from the car window. I really feel for the people cued, sitting in hot cars, this govt!
  • Andrew
    405
    Payment is where it gets tricky.

    An employee cannot be made to stay at home if they only have 'flu like symptoms". If an employer insists then this would likely be treated like a "suspension" and employees can't be disadvantaged while suspended. So the time off work would likely be on the employers account - not out of the employees leave entitlement.

    And "flu like symptoms" does not mean a person has flu, or covid.

    As for the Covid Leave Support Payment your employer is going to need an instruction from Min of Health that the employee must self isolate. An employee going "I'm a bit crook with flu like symptoms so going to have a week off work" isn't going to cut it. So total period of absence wil come out of employees leave entitlement.

    Also worth noting is the Leave Support Payment is $600 for two weeks - not per week. Unlike the wage subsidy in previous years. So expect employees to want to be at work.

    As an aside I am still astounded how many "crook people" are still desperate to get a RAT given their unreliability. I suppose its a first world problem when you have the worried well lining up for such things.
  • Trudy Downes
    92
    Thanks for running a control case and sharing with us. I am trying to get my lot on board with an approach like this, but don't have any positive cases to play with yet, but I know they are out there!
  • Jane
    92
    Please don't think of your people with confirmed covid as your samples to test. Maybe wait until you have it and run your experiment on yourself.
  • Trudy Downes
    92
    Thank you for your response - I had to laugh thinking of myself as a mad scientist subjecting people to cruel and inhumane practices. Let me rephrase... my people deal better with emperical data based on the environment and people they love and care about. Being able to have a control case would be beneficial for this approach, and it truly helps take some of scariness away.

    None of us have walked this path before.
  • Jane
    92
    Sure, but a few million million in the world, and a few million RAT tests in NZ have already been done and the results reported. Not sure what is so scarey about the RATs that requires control cases or empirical data. It is like a pregnancy test, but instead of testing for a hormone it is testing for a protein made during a viral infection, and it uses a nose swab not wee.

    The process around RAT testing is more important than taking the RAT itself. Rather than testing the tests, concentrate on the process, supporting your people and the means for getting your business through the next few weeks, there is plenty enough to do as I am sure you are doing already.
  • Aaron Marshall
    118
    Right, so here's my personal experience of the limitations of RAT testing:
    My wife had to travel to Auckland for work, and so, before having contact with anyone else outside our household after returning home, did a RAT test on day 3 - returned negative (Thursday evening)
    Friday night she had minor symptoms, so did a test Saturday morning and it came back positive.

    I had minor symptoms at this time as well, so did a RAT test as advised, and it came back negative.
    Monday evening, more symptomatic, and I did another test - still negative. I decided to ignore the test, and class myself as positive (i hadn't had contact with anyone to catch anything else)

    The next Saturday morning (after symptoms had subsided) I did another RAT test as it should have been the end of my isolation, and this one finally came back positive, but since I was asymptomatic, I was able to leave isolation?

    So, RAT tests alone aren't a sure-fire way of detecting covid (particularly in vaccinated people). From what I've read, if you're vaccinated, you'll have a faster response, and earlier symptoms, sometimes before RAT test sensitivity.
  • Andrew
    405
    RAT's are unreliable. There are people turning up in hospital who had negative RAT's but subsequently tested positive.
  • Jane
    92

    I would add, RATs are most unreliable in those with a low viral load.
    Rats are more reliable with a high viral load, and these are the most likely people to be infectious.

    PCR tests for the virus.
    RATs test for viral load and therefore level of infectiousness.
    2 different things.
    People want them to mean the same thing, but they don't. Timing of the testing through the viral infection matters as does how the infection progresses in each person.

    Pregnancy tests also return negative tests before your period is due, even if you are pregnant, because the levels of pregnancy hormone in your wee is too low to be detected. So a negative pregnancy test, does not always mean that you are not pregnant, it might mean that you are testing too early.

    Everyone accepts a neg pregnancy test may have been taken too early in the course of the pregnancy, it shouldn't be too hard to correlate that to a neg RAT test being taken too early in the course of a symptomatic infection, there may be a pos RAT test to come.
  • Jane
    92
    If I am reading your post correctly, you are a household contact of a positive case, so needed to test on day 3 and day 7 while isolating. Your viral load was high enough to be detected by RAT on your day 7 test. That would mean you need to stay in isolation, regardless of symptoms.
    Your wife, however has done her 7 days isolation since testing pos, and can leave isolation so long as she has no further symptoms.
  • Aaron Marshall
    118
    No, isolation ended at the end of symptoms. Isolation starts at either a positive test or onset of symptoms, and ends at a negative 7 day test (if no symptoms) or the end of symptoms if symptomatic.
    If you have an initial positive test, then there is no further test required to end isolation.

    Despite being symptomatic, and with two negative RAT tests, I was told that I couldn't get a PCR test because they weren't doing them. The impression I got was that MoH had given up trying to confirm cases.
  • MattD2
    339
    The next Saturday morning (after symptoms had subsided) I did another RAT test as it should have been the end of my isolation, and this one finally came back positive, but since I was asymptomatic, I was able to leave isolation?Aaron Marshall
    ↪Aaron Marshall If I am reading your post correctly, you are a household contact of a positive case, so needed to test on day 3 and day 7 while isolating. Your viral load was high enough to be detected by RAT on your day 7 test. That would mean you need to stay in isolation, regardless of symptoms.
    Your wife, however has done her 7 days isolation since testing pos, and can leave isolation so long as she has no further symptoms.
    Jane
    Unless since Aaron was originally symptomatic his timeframe could be consider from when he was first symptomatic... and therefore day 7 is the day he took the test...

    And this goes back to what you were saying as the test are not measuring if you have Covid but if the nasal (or oral) viral load is above a threshold level (and then correlating/interpreting that as being infectious) - it is about managing the risk of spreading the infection rather than counting who has Covid or not.

    If it were me I would test again before leaving my home (only leaving once I had a negative test) - but keep monitoring for reoccurring symptoms and taken extra precautions for the next week such as face masks when in close contact with anyone else and religious hand washing / sanitising.

    I feel like our current "rules" fit the typical "90%" of situations, but there is no plan for how we deal with the "10%" of curveballs that need a bit more effort to assess and manage the risk - i.e. it is like a blanket PPE policy on a construction site, it makes instructing and enforcing the policy easy but causes (sometimes large) issues in circumstances when the policy doesn't practically fit the work.
  • Jane
    92
    f it were me I would test again before leaving my home (only leaving once I had a negative test) - but keep monitoring for reoccurring symptoms and taken extra precautions for the next week such as face masks when in close contact with anyone else and religious hand washing / sanitising.MattD2

    yeah, knowing what I know about the testing, there is no way I would be leaving the house straight after having a pos rat test. That goes against every public health measure we have in place, and I would love to know if it was a hcw who said that leaving the house straight after getting a pos rat was ok.
    Personally, I would encourage people to stay home for 7 days after having a positive rat test. And there is no way we would accept going to work with a pos rat that day in my workplace or my husbands workplace.
    Rats can throw up false pos's, but there are protocols to deal with that. Best be cautious.
  • MattD2
    339
    That goes against every public health measure we have in place, and I would love to know if it was a hcw who said that leaving the house straight after getting a pos rat was ok.Jane
    (On a technicality) that is essentially the advice that the MoH / Covid-19.govt.nz website is giving:
    Friday is your Day 0
    What you need to do:
    You need to self-isolate until Friday next week (Day 7).
    You can leave self-isolation on Saturday next week.

    What your household needs to do
    The people you live with are Household Contacts. They must isolate with you until you leave self-isolation.
    They must get a test this Monday (Day 3) and Friday next week (Day 7).
    If their Day 7 test is negative and they have no new or worsening symptoms, your Household Contacts can leave self-isolation on Saturday next week.
    If their Day 3 or Day 7 tests are positive, they need to begin 7 days of isolation as someone with COVID-19, and follow the guidance for people who are positive.
    covid19.govt.nz
    And given my understanding the the reporting of being a positive case is essentially automated now there would be no other advice given apart from this.
  • Jane
    92
    The positive covid case can leave after 7 days with no further testing.
    The household contact can leave with a negative day 7 AND no worsening symptoms.

    The household contact does not get to leave with a positive day 7 test.
    Which bit of your quote above says the household contact can leave with a positive day 7 test?
  • MattD2
    339
    Which bit of your quote above says the household contact can leave with a positive day 7 test?Jane
    Because once the household case tests positive they stop being a household case and are now considered a positive case - and then you need to assess the positive case's isolation period, this being the earlier of either; the positive RAT, or becoming symptomatic. It could be reasonable to considered that the positive RAT result is due to being infected at the same time as his partner but a lag in the build up of sufficient virial load (or inaccuracy with previous RATs) resulted in negative results until this time, i.e. the onset of the symptoms relating to the positive RAT were 7 days prior to the test.

    As I said - this is outside of the typical scenarios that the general self-isolation/testing rules cover but since there is no other advice given (or more correctly no scope of when / when not to apply the general rules) we are left in the uneasy situation of technically a person that has just returned a positive RAT also been considered suitable to leave isolation.
  • Jane
    92
    Because once the household case tests positive they stop being a household case and are now considered a positive caseMattD2

    in this case, the household case hasn't become a confirmed covid case until they tested pos at the day 7.
    They were symptomatic and tested neg on Day 0 and 2. The Day 7 test requirement for being a household contact doesn't just disappear because of symptoms coming and going.

    This is not a technical situation at all, it is quite clear that the day 7 test is positive and the person is now a confirmed covid case (looking like asymptomatic and yet carrying spike protein and virus in their nose), and should be at home.
  • Aaron Marshall
    118

    No, it is confirmed at day 7, but the iso period starts from the beginning of symptoms.
    My frustration was that it was impossible for me to get any other sort of test at all. I was specifically told that I couldn't get a PCR test, despite obviously being outside the typical profile.
    From what I understand, the RAT test will continue to give a positive result well after the infection ceases to become active

    I know that none of this make sense, but we're dealing with a government department here...
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