To think there is absolutely no point in doing a Covid test?

[PearPickingPorky]

DH has been feeling unwell for a few days, started feeling shivery over the weekend (but no temperature), and an upset stomach. He's a key worker so he booked himself a Covid test on Sunday (thinking sensible to rule that out, even though he didn't think it was that) at one of the drive-through test centres and got an appointment immediately.

He has an underlying health condition so he also called GP on Monday for a blood test to check if it is the other condition, which they did.

Got his results last night for Covid by text, it came back negative.

His GP phoned back with his blood results this morning and said she thinks it is Covid. He said he'd just been tested and it was negative. She says to ignore it and self-isolate.

The Covid results text specifically says no need to self-isolate and go back to work. GP says no, because the tests are not reliable.

Seriously, what is the point of the test then? If DH hadn't also had a blood test (and thus his GP became involved) then he'd be back at work, potentially spreading it around (if it is Covid).

Seriously, what's the point of doing 100,000 tests a day if 30% of them (GP says) are wrong?

There is little point. That's why the govt tried to not bother but have bowed to pressure

I haven't found any good studies which look at

a) Doing swabs by yourself vs a professional doing them
b) Comparing RT-PCR with confirmed cases of Covid-19 via other means.

I haven't seen any figures for sensitivity. I definitely haven't seen any figures suggesting 70% sensitivity.

The one thing that is virtually guaranteed is that a positive test means you have it.

The 70% accuracy for a negative swab is correct. It's not great but it is the best we have

What are you meaning by that?

How many people out of 100 who have Covid-19 do you think would be detected with a swab test?

Certain blood levels can be indicative of COVID-19. I’m assuming that’s what the gp noticed.

The tests cannot be relied on and false negatives are very common. Especially if the test is taken outside of the 24-48 hour window from symptom onset. If a gp says to isolate ?covid then you should do so.

My brother and his partner and kids just got a test they haven't even been out hardly she's just got a sore throat and went and got tested didn't know it was that easy now

My brother and his partner and kids just got a test they haven't even been out hardly she's just got a sore throat and went and got tested didn't know it was that easy now

That's the danger with setting a target - because then the target becomes the objective and the idea behind the target is lost.

There is no point in testing people who are very likely to be negative - unless the point is to say that they have hit the testing target.

Godhart's Law

towardsdatascience.com/unintended-consequences-and-goodharts-law-68d60a94705c

There are several problems with the Covid test.
Firstly, calling it a “swab” is a misnomer. It should be a painful puncture deep into the nasal mucosa. Just rubbing it inside the nose will invariably give a false negative.
When I was admitted to my local Covid ward, the doctors were repeating all the samples themselves, saying the nurses weren’t stabbing hard enough!
Secondly, there is a “window” for sampling, when you are more likely to detect a positive. If you have been ill for several days before testing, you may miss the boat in trying to pick it up. Similarly, too early may show a false negative.
I would have a high index of clinical suspicion. If you have textbook Covid symptoms - altered sense of taste/smell, high temperature/night sweats, breathlessness and severe “air hunger”, or rough unproductive cough, then I would treat that as Covid and isolate, whatever the test result came back as.
I was hospitalised on oxygen at day 13 of my illness, exhausted after fighting to breathe and self proning at home with almost no sleep for that time. My test on admission was negative, but my consultant was in no doubt I had the virus. My protracted recovery (ill for nearly seven weeks) would also tend to that conclusion.
Incidentally, the OP’s GP may have seen other suggestive features on the blood tests - Covid tends to affect the ALT liver enzyme level and also white blood count.

I got a letter from Imperial College inviting me to be sent a test. I don't think I'll bother. It all sounds a bit pointless.

Maybe a blood test would be more accurate if one can be done?

When I was admitted to my local Covid ward, the doctors were repeating all the samples themselves, saying the nurses weren’t stabbing hard enough

Sounds painful - and yet they are sending out home testing kits to people.

I got a letter from Imperial College inviting me to be sent a test. I don't think I'll bother. It all sounds a bit pointless.

IC are doing this for research, partly to help with their modelling of the disease in the population but doubtless they will also be looking at how useful this testing strategy is. That's the point.

*What are you meaning by that?

How many people out of 100 who have Covid-19 do you think would be detected with a swab test?*

Relatively small study but this gives an idea:
jamanetwork.com/journals/jama/fullarticle/2762997

As a nurse practitioner and someone who was swabbed twice a proper nasopharangeal swab should be unpleasant and i certainly don't think I could take an effective self swab.
GP may have seen other markers for covid in blood for example elevated LDH, Ferritin and CRP.

I used all my energy going for a test on Saturday. Still no results. I felt horrendous but slowly getting better.
If this isn’t Covid19 then it’s a bloody awful virus and I’m in no way ready to go back to work.

I’m a doctor. Did he have his full blood count checked? A fair few people have low lymphocytes on their full blood count when covid positive (with negative swabs). I suspect that was what the GP was concerned about.

We reswab inpatients if there is still a high clinical suspicion. I think your GP is being very sensible.

Also as @Mumof1I a high CRP is also not uncommon and can indicate covid. White cell count often quite normal unless co-existing bacterial infection.

Sheepissheep, there is no way I am confident or competent enough to self swab so it is pointless. What would be the point in all those incorrectly administered tests?

The idea of self swabbing terrifies me! I’ve swabbed patients and I don’t think anyone could be aggressive enough to get a sufficient sample on themselves or family members, we’d just end up with lots of false negatives. Hopefully swabbing centres with continue.

What would be the point in all those incorrectly administered tests

To say they have hit the target?

Oh of course, targets. Good point. They can stuff their targets.

Yanbu. The tests are nothing but a PR exercise for the government (not a very well executed one given they are failing to meet their own arbitrary targets). They are unreliable and in any case without an effective contact tracking system all they are doing is keeping score. The data is not being shared with GPs who are dealing with the majority of cases but cannot see an overview of where clusters are appearing. It's an absolute joke and the media are not talking about it nearly enough.
Thousands like your DP are being treated for suspected covid (e.g. non asthmatics being prescribed ventalin inhalers to help with breathing difficulties) and they are not even being recorded in the official figures because there's no point testing them.
I expect to see a big second spike in the next couple of weeks thanks to the ridiculous government guidelines this week.

A lot of people are not experiencing a significant cough or fever either so when they go on 101 it is not picking it up as potential covid and therefore not triggering isolation. This is how it keeps spreading. 627 dead today.

Yes high CRP, high ferritin and low...something. Maybe lymphocytes.

Unfortunately, those markers are the same markers which would suggest his other health condition is active at the moment too.

These Covid tests are of very limited use.

@JimMaxwellantheshippingforcast

Norovirus results in about 685 million cases of disease and 200,000 deaths globally a year - who knew !

The worst things I have had as an adult were the flu & Norovirus.

@marinintheuk

Wow, I had no idea it was so high

A lot of people are not experiencing a significant cough or fever

Weeks of coughing for me but no fever. So the temp tests for airlines etc would be useless.