Erroneous laboratory results: what clinicians need to know

[helvella]

This is the sort of paper which, at one and the same time, is very difficult to apply (especially by us - as the people with the disorders), and yet potentially so important.

One test resulted affected like this could see the person treated not just poorly, but in precisely the opposite way to what they require.

But if only one in 200 tests might be affected, that is a small enough number that individual doctors might rarely be aware of an affected result occurring, nor know what to do about them. And labs will surely (in general) not be particularly receptive of what amount to allegations they got something wrong. An awful lot of these results will simply pass by - unnoticed, unexamined, unverified. At most a shrug.

Erroneous laboratory results: what clinicians need to know

Author links open overlay panelYasmin Ismail BSc MD MRCP (Specialist Registrar in Cardiology) 1, Abbas A Ismail BSc MSc MD FRCP (Consultant Rheumatologist) 2, Adel AA Ismail BPharm PhD FRCPath (Retired Consultant in Clinical Biochemistry and Chemical Endocrinology) 3

doi.org/10.7861/clinmedicin...

open access

ABSTRACT

Laboratory tests such as ‘conventional biochemistry' are analytically robust and trusted, however, some common tests performed by immunoassays, eg thyroid function tests, are inherently more prone to analytical interference, giving rise to incorrect results. Interfering antibodies capable of causing potentially misleading results in immunoassay varied from about 0.4% to 4%. Furthermore, this form of interference cannot be predicted a priori and cannot be detected even by most stringent laboratory quality control assurance schemes because it is unique to an individual sample. Since more than 10 million immunoassay tests are carried out yearly in the UK alone, the impact of this problem on delivering appropriate patient care can no longer be ignored. Clinicians tend to perceive all laboratory data in the same light. Because of this, increased awareness of the inherent limitations of these laboratory tests should trigger a more measured and thoughtful approach, thus ensuring patients receive appropriate investigations and treatment.

Previous article in issue

Next article in issue

KEY WORDS

erroneous analytical results

immunoassay

interference

laboratory tests

wrong laboratory results

Open access - I downloaded the PDF

sciencedirect.com/science/a...

[Regenallotment Ambassador]

is this the 🐭 antibodies again?

[helvella in reply to Regenallotment]

Might be - sometimes - but lots of other possibilities!

🐜-i-🧍🚶🕴️🧍🏃🚶‍♀️🤸‍♀️🧍‍♀️🏌️

[Regenallotment Ambassador in reply to helvella]

That’s one for the work quiz!

[elaar]

I briefly mentioned issues with immunoassay testing just a few days ago, there's lots of different possible issues with it, especially with FT3 measurements where the concentration is so low.

It's not just autoantibodies, but from memory there's also problems with the way they manipulate the thyroid hormones from the binding proteins for measurement, which can lead to inaccuracies in cases where there is also Liver/Kidney dysfunction (which is fairly common to some degree with Thyroid diseases).

[Jayneywales]

I used to work in this area. That’s why I get soooo cross on results driven only medication changes. And remember- when setting ‘normal’ ranges - the base data used is NOT a cross section of the population as a whole but people who have had their blood collected for a reason in a medical setting who by that very nature are not medically ‘normal’ in any event! GRrrrrrr

[Sleepman]

Thank you Helvella.

One test is never ideal to be more certain of something ... need repeatability from more tests.

But then more likely to get a duff result to explain.

youtu.be/Z0Z-zYF3OP4?si=CqE...(Not working as expected?)

Just rewatched this at 1.5 speed.

Expert on thyroid blood tests explaining some of the inner workings. Dr David Halsall

Listen past the praise of TSH tests !

1 in 20 will be outside the normal range as its a distribution.

Reminds us that blood tests are only part of the story in identifying disease.

Interesting that labs test same sample all round the UK to check results.

If you look after a lot of rabbits and mice it can interfere with immunoassay. Ant-i-bodies ...

As we know biotin affects things too.

[Cornwaller]

Really important data. It bugs me that doctors, and even on this forum to some extent, that blood results are treated as the gold standard metric whilst actual disease symptoms ie the manifestation of the disorder are either ignored or at best secondary. The reverse would be better!

Obviously to consider all the patient history holistically to gain a "map" of the reality would increase the likelihood of identifying outliers which need checking and thereby reducing treatment errors.

[birkie]

Doing blood work for thyroid conditions intrigued me when I was eventually diagnosed [ graves disease in 2018 ], before my initial diagnosis I presented myself to my gp on numerous occasions , with what were undoubtedly symptoms of an overactive thyroid. Unfortunately I was dealing with a very unprofessional gp who couldn't diagnose me he blamed the menopause🤦‍♀️, I did however in 2014 get him to perform bloods and i again asked if these symptoms could be thyroid related, he came round behind me and examined my neck saying " you don't have a goiter so theres nothing wrong with your thyroid " all I can remember is being told NO FURTHER ACTION REQUIRED.

I since found out when I did have those bloods done he sent them to an endo who reported..this lady as a short suppressed TSH with episodes of thyroditis this probably being subclinical hyperthyroidism..[ I never saw this report until 2020 in my records]

Obviously graves in an auto immune condition as is some other thyroid conditions, I never had thyroid antibodies done at all, until I was rushed into hospital in thyroid storm, my antibodies were off the scale, how long had they been like that?

So...in thyroid auto immune conditions if I'm correct we attack our thyroid in my case when I was in an attack I dumped large amounts of T3, T4 into my blood stream [ in attack mode] rendering me hyper, this in the first year or so happened on some occasions but not all , and I started to refer to the attacks as my flare ups.

I found when bloods were taken it seemed I was not in an attack and inevitably my bloods were normal, now I must state my gp only did 2 sets of thyroid bloods from 2014 up until I was diagnosed 2018, as my one test was normal he would not test my thyroid bloods again 😡 awful gp...just awful.

Now fast forward to 2018 I collapsed AGAIN and were taken ..in the flare up to the surgery where bloods taken confirmed hyperthyroidism ( graves)👍

This is the dilemma...a gp sees a short suppressed TSH or a high TSH on one test then repeats it [ as he should] it comes back normal and that's it, the gp or endo automatically think everything is OK and [ as I found] you have to keep bugging them to perform another thyroid bloods , because you may have not been in a flare up or an attack.

This is why I was never diagnosed until it was to late, lost my thyroid in 2019 to the incompetence of my awful gp and endocrinologist, they just don't understand the complexity of the thyroid, and thyroid blood tests.

I love reading helvellas posts because after reading them I think....yes I can totally relate to that!!!

❤️

[humanbean]

Another major problem with thyroid testing these days is that, since labs only test TSH now, they can't diagnose Central Hypothyroidism (CH).

CH presents with a low Free T4 and low Free T3 and a much lower than expected TSH. Generally TSH in CH can be anything from under-range to slightly over-range in the milder cases.

Someone with CH who only gets a TSH measured could be diagnosed with hyperthyroidism if no Free T4 and/or Free T3 are measured.

I have CH at the milder end of the scale. My TSH has never reached 6, but my Free T4 and Free T3 were 8% through the range and 11% through the range respectively. My doctors, naturally, thought I was perfectly healthy. I have seen people quoting results on the forum similar to my Free T4 and Free T3, but in one case the TSH was 10, and in another it was 30. This is why I think TSH-only testing is completely unethical and sadistic. But doctors use the excuse that CH is rare - and it's easy to say that when the proper testing is not done.

Some years ago I had a CT or MRI scan, can't remember which, which showed my pituitary was completely flat (which may indicate I have a condition known as "empty sella"), and apparently this is not uncommon. I've never had tests to see whether my pituitary hormones have been affected, but my TSH definitely has in my opinion.

For anyone who is interested this link, published May 2024 and open access, is worth investigating :

Title : A Comprehensive Review of Empty Sella and Empty Sella Syndrome

Link : endocrinepractice.org/artic...

The abstract says :

Incidental radiographic findings of an empty sella are prevalent in up to 35% of the general population. While empty sella was initially considered clinically insignificant, a subset of patients exhibits endocrine or neuro-ophthalmologic manifestations which are diagnostic of empty sella syndrome (ESS). Recent studies suggest that more patients are affected by ESS than previously recognized, necessitating a deeper understanding of this condition. This comprehensive review describes a practical approach to evaluating and managing ESS.