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Lateral flow cassette

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88V8
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Lateral flow cassette

#506879

Postby 88V8 » June 13th, 2022, 3:08 pm

A first... OH having had a 'cold' for a week now, she carried out our first ever LF test.
Which was negative.

The copious instructions did not mention what to do with the used cassette, and I cannot find any comment online or in the Lemon. Presumably not wash it.

Do we just seal it up until wanted again?

V8

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Re: Lateral flow cassette

#506906

Postby staffordian » June 13th, 2022, 4:30 pm

They are single use, so chuck it.

There is usually a sealable plastic bag, one for each test in the pack, into which all the potentially infected stuff is placed.

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Re: Lateral flow cassette

#506915

Postby swill453 » June 13th, 2022, 4:58 pm

What is the "cassette"? I've done many lateral flow tests but never used any part called a cassette.

Scott

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Re: Lateral flow cassette

#506918

Postby DrFfybes » June 13th, 2022, 5:11 pm

swill453 wrote:What is the "cassette"? I've done many lateral flow tests but never used any part called a cassette.

Scott


I presume they mean the plastic thing you drip the sample in to.

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Re: Lateral flow cassette

#506919

Postby swill453 » June 13th, 2022, 5:14 pm

DrFfybes wrote:
swill453 wrote:What is the "cassette"? I've done many lateral flow tests but never used any part called a cassette.

I presume they mean the plastic thing you drip the sample in to.

The OP implies it's something to be used again.

Maybe mistakenly, of course.

Scott.

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Re: Lateral flow cassette

#506921

Postby monabri » June 13th, 2022, 5:18 pm

June 2021....384 million kits. How much plastic would this equate to in land fill? Shouldn't the kit be classed as medical waste?

https://www.bmj.com/content/372/bmj.n287

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Re: Lateral flow cassette

#506928

Postby Hallucigenia » June 13th, 2022, 5:31 pm

monabri wrote:June 2021....384 million kits. How much plastic would this equate to in land fill? Shouldn't the kit be classed as medical waste?


Well I've just weighed one at 3.83g, so that's 1471 tonnes. Although not all will go to landfill, ours gets incinerated.

Hospitals would send anything like that for disposal as medical waste, but I guess it's relatively low hazard - most will be negative and so have no virus on them, I suspect that even if there is virus the buffer denatures it so they won't be viable, and the virus isn't that stable, most won't survive to binday anyway.

That said, I would be careful of disposing of the swabs and plastic tests if I was positive, bagging them etc.

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Re: Lateral flow cassette

#506948

Postby redsturgeon » June 13th, 2022, 6:56 pm

All our used covid testing materials are collected as medical waste.

John

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Re: Lateral flow cassette

#506954

Postby jfgw » June 13th, 2022, 7:23 pm

The ones I have had (three different types) have all come with self-seal polythene bags for the rubbish. These then get thrown in the bin.

How many of you treat disposable handkerchiefs as clinical waste?

Do you have a yellow bag for sanitary towels, condoms and moist toilet wipes?


Julian F. G. W.

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Re: Lateral flow cassette

#507018

Postby servodude » June 14th, 2022, 12:47 am

jfgw wrote:How many of you treat disposable handkerchiefs as clinical waste?

Do you have a yellow bag for sanitary towels, condoms and moist toilet wipes?


Julian F. G. W.


That reads like the worlds worst personals add! ;)

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Re: Lateral flow cassette

#507048

Postby Mike4 » June 14th, 2022, 8:44 am

jfgw wrote:The ones I have had (three different types) have all come with self-seal polythene bags for the rubbish. These then get thrown in the bin.


I'm pretty certain my own test kit instructions specifically state to put all the bits and pieces used in the test into the ziplock polythene bag supplied and put it in the (presumably general waste) bin.

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Re: Lateral flow cassette

#507075

Postby 88V8 » June 14th, 2022, 9:40 am

swill453 wrote:
DrFfybes wrote:
swill453 wrote:What is the "cassette"? I've done many lateral flow tests but never used any part called a cassette.

I presume they mean the plastic thing you drip the sample in to.

The OP implies it's something to be used again.
Maybe mistakenly, of course.

Indeed.
Now I put my specs on, I see that we have 7 cassettes, not 1.
So it's a throwaway.
All 7 sealed in little bags, OH thought they were.... dunno what.

Anyway, false alarm. :oops:

Yes, the waste goes in a ziplock.

The process was eye-openingly fiddly. The notion of doing this every morning before setting off for work.
Have to admire anyone who did that.

V8

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Re: Lateral flow cassette

#507085

Postby monabri » June 14th, 2022, 9:56 am

servodude wrote:
jfgw wrote:How many of you treat disposable handkerchiefs as clinical waste?

Do you have a yellow bag for sanitary towels, condoms and moist toilet wipes?


Julian F. G. W.


That reads like the worlds worst personals add! ;)


WELL...if YOU do, you need new Cillit Bang!

;)

Nappies do have a separate bin (don't wear 'em yet).

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Re: Lateral flow cassette

#507100

Postby Mike4 » June 14th, 2022, 10:21 am

88V8 wrote:The process was eye-openingly fiddly. The notion of doing this every morning before setting off for work.
Have to admire anyone who did that.


I suspect for people doing them on a regular basis, 90% of the fiddly steps get dispensed with.

For example, a villager here who is associated with the ambulance service told me a positive result actually shows up immediately the test is executed, before the fluid has even soaked along the blotting paper as far as the control line. So if the control line shows up but no 'positive' line, you know it will still be a negative result after the 15 minute wait required by the instructions before reading the result, so no need to bother with the wait. 'Knowing', or believing this to be true and relying on it immediately strikes out the 15 minutes' waiting time and makes self-testing much quicker and easier than your own experience.

'Information' like this that may or may not be true in practice but it gets passed around socially, and quite probably significantly reduces the reliability of negative LFT results.

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Re: Lateral flow cassette

#507129

Postby Julian » June 14th, 2022, 11:34 am

Mike4 wrote:
88V8 wrote:The process was eye-openingly fiddly. The notion of doing this every morning before setting off for work.
Have to admire anyone who did that.


I suspect for people doing them on a regular basis, 90% of the fiddly steps get dispensed with.

For example, a villager here who is associated with the ambulance service told me a positive result actually shows up immediately the test is executed, before the fluid has even soaked along the blotting paper as far as the control line. So if the control line shows up but no 'positive' line, you know it will still be a negative result after the 15 minute wait required by the instructions before reading the result, so no need to bother with the wait. 'Knowing', or believing this to be true and relying on it immediately strikes out the 15 minutes' waiting time and makes self-testing much quicker and easier than your own experience.

'Information' like this that may or may not be true in practice but it gets passed around socially, and quite probably significantly reduces the reliability of negative LFT results.

For me the thing that made the test fiddly and time consuming at first was simple unfamiliarity leading me to carefully lay out what was needed, double check that I had correctly identified everything that I was going to need, going back to read the instructions again, and then double-checking that I was doing the right thing at each step. Once I'd done the test a few times though it became pretty routine with no need to look at any instructions. I can also imagine that many people doing it every morning before work probably found ways to integrate the pause before the result into their morning routine e.g. the theoretical wait time for the result being about the time it took to eat their bowl of cereal and the time taken to do the initial swab, swirl around in the tube and put the drops onto the test strip might perhaps be about the time needed for the kettle to boil. Those are the sorts of tricks I would have looked for if I was still working and needed to incorporate daily testing into my morning routine.

That villager's optimisation (you only need to wait long enough for the control line to show up to validate a negative) makes perfect sense to me on the basis of my understanding of how the tests work. It makes me wonder why the instructions (as I remember them, it's been a while since I tested) are worded as they are. I suppose it's just simpler and potentially less confusing to say "wait 15 minutes" (or however long it says) rather than something like "wait 15 minutes but if the control line shows up sooner and the test line is clear then the test is negative". Simplicity matters in instructions that need to be clearly understood by pretty much the whole population.

- Julian

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Re: Lateral flow cassette

#507139

Postby Watis » June 14th, 2022, 12:10 pm

Mike4 wrote:
88V8 wrote:The process was eye-openingly fiddly. The notion of doing this every morning before setting off for work.
Have to admire anyone who did that.


I suspect for people doing them on a regular basis, 90% of the fiddly steps get dispensed with.

For example, a villager here who is associated with the ambulance service told me a positive result actually shows up immediately the test is executed, before the fluid has even soaked along the blotting paper as far as the control line. So if the control line shows up but no 'positive' line, you know it will still be a negative result after the 15 minute wait required by the instructions before reading the result, so no need to bother with the wait. 'Knowing', or believing this to be true and relying on it immediately strikes out the 15 minutes' waiting time and makes self-testing much quicker and easier than your own experience.

'Information' like this that may or may not be true in practice but it gets passed around socially, and quite probably significantly reduces the reliability of negative LFT results.


Your concerns are correct, Mike4!

Using another brand of test that has a 30 minute wait time, the first positive test I had was still clear at 30 minutes - and it was only when I went to register it on the Covid site at 40 minutes that I noticed that a faint pink line had appeared.

But, for the next few days, the positive red line did appear very quickly.

Watis

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Re: Lateral flow cassette

#507994

Postby XFool » June 17th, 2022, 8:58 pm

Julian wrote:For me the thing that made the test fiddly and time consuming at first was simple unfamiliarity leading me to carefully lay out what was needed, double check that I had correctly identified everything that I was going to need, going back to read the instructions again, and then double-checking that I was doing the right thing at each step. Once I'd done the test a few times though it became pretty routine with no need to look at any instructions.

Sounds familiar!

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Re: Lateral flow cassette

#508236

Postby 9873210 » June 19th, 2022, 9:30 am

Hallucigenia wrote:
Hospitals would send anything like that for disposal as medical waste, but I guess it's relatively low hazard - most will be negative and so have no virus on them, I suspect that even if there is virus the buffer denatures it so they won't be viable, and the virus isn't that stable, most won't survive to binday anyway.

That said, I would be careful of disposing of the swabs and plastic tests if I was positive, bagging them etc.


I'm more concerned about the reagents that exist in any test used, unused, positive or negative; rather than just virus in a positive test.

AIUI at least some of the tests use sodium azide, which is at least moderately unpleasant. It's usually good to read and follow any instructions. If no instructions I bag them and keep them away from children, pets and idiots.

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Re: Lateral flow cassette

#508245

Postby servodude » June 19th, 2022, 10:42 am

9873210 wrote:
Hallucigenia wrote:
Hospitals would send anything like that for disposal as medical waste, but I guess it's relatively low hazard - most will be negative and so have no virus on them, I suspect that even if there is virus the buffer denatures it so they won't be viable, and the virus isn't that stable, most won't survive to binday anyway.

That said, I would be careful of disposing of the swabs and plastic tests if I was positive, bagging them etc.


I'm more concerned about the reagents that exist in any test used, unused, positive or negative; rather than just virus in a positive test.

AIUI at least some of the tests use sodium azide, which is at least moderately unpleasant. It's usually good to read and follow any instructions. If no instructions I bag them and keep them away from children, pets and idiots.


Quick tip:
If more than one person is doing them at a time you can fit both sets of the paraphernalia in one bio-hazard bag
- leaving the other free to be used for carrying olbas pastilles in the pocket, without the risk of spreading sugar, but affording the joy of funny looks in public

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Re: Lateral flow cassette

#508840

Postby Hallucigenia » June 22nd, 2022, 2:08 pm

9873210 wrote:I'm more concerned about the reagents that exist in any test used, unused, positive or negative; rather than just virus in a positive test.

AIUI at least some of the tests use sodium azide, which is at least moderately unpleasant. It's usually good to read and follow any instructions. If no instructions I bag them and keep them away from children, pets and idiots.


Some of the anti-health mob have seized on azide as another justification for their stance, but in reality the risks are not that great - we're talking <0.5ml at a concentration of 0.01-0.1%. It's theoretically possible that if a child drank the full volume of one of the high-azide test vials then they might suffer a drop in blood pressure - the amount is below what's been used in testing. But the US poison reporting system had 153 reports of human exposure to test kit reagents in 6 months and most had no ill effects - the risks are probably less than eg peanuts, do you bag your peanut butter jars?

This goes into more detail :
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8786400/


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