Classification Criteria vs. Diagnosis Criteria

[AtopicGuy]

I learned something new while reading this article on PMR:

cmaj.ca/content/193/46/E1770

It says "The European League Against Rheumatism (EULAR) and American College of Rheumatology (ACR) criteria can distinguish polymyalgia rheumatica from mimicking conditions."

However, I then clicked on the tab marked "Responses" and found the following comment by Dr Megan R W Barber MD PhD:

"I read this article with interest. Thank you for drawing attention to this often delayed diagnosis.

"Regarding point 3, the authors do not appropriately distinguish between classification and diagnostic criteria when discussing the 2012 EULAR/ACR provisional classification criteria for PMR.

"Classification criteria are designed solely to select a homogenous sample of patients for clinical research studies and are not intended to diagnose patients. They are often not sensitive enough for this purpose and fail to capture the heterogeneity intrinsic to rheumatic diseases (Aggarwal et al. 2015).

"In fact, the 2012 EULAR/ACR provisional classification criteria to which the authors refer had a sensitivity of just 68% for a score ≥4 in their original cohort (Dasgupta et al. 2012) and the manuscript clearly notes that “these criteria are not meant for diagnostic purposes.”

"When diagnosing PMR, rheumatologists take into consideration many factors that are not reflected in the provisional classification criteria, such as patient response to a trial of steroids.

"Confusion between classification and diagnostic criteria is common, but it is a crucial distinction. Relying on classification criteria at the bedside results in missed diagnoses."

I then found the quoted article by "Aggarwal et al. 2015":

acrjournals.onlinelibrary.w...

This explains in detail why most epidemiological studies should apply strict Classification Criteria when choosing patients to study against a control group. This is to minimise the chance that misdiagnosed cases invalidate the results.

Doctors should use much looser Diagnostic Criteria to avoid missing cases that do not meet all the Classification Criteria. EULAR/ACR responded that they do not produce such DC, only CC.

This confusion may go some way to explain the huge variations in diagnostic criteria claimed for PMR and other diseases. At the foot of the Responses tab, Dr Patricia A Forbes MD Chb describes her own experience of PMR despite not testing positive for CRP or ESR:

"I had a classical case which responded to prednisone. I had a shorter recurrence several months later. I was one of the percentage of patients who had normal ESR and CRP. No further recurrence in 2 years. I do have finger arthritis."

According to the original study, she should not have been diagnosed or treated for PMR because she did not meet the EULAR/ACR criteria. It would seem those denying the existence of atypical PMR may be relying on the wrong set of published criteria. I wonder whether that includes this very strict NHS guidance, which demands "all" criteria be met? It reads very much like a set of CC:

nhs.uk/conditions/polymyalg...

[PMRpro Ambassador]

We've been saying this for years. But we are "only" patients so very few rheumies listen and the ones that do are generally fighting a losing battle against their colleagues who dismiss PMR as unworthy of their attention as it is a temporary condition that burns out in a couple of years - a belief that is totally incorrect, But only elderly ladies suffer from it and they aren't significant enough to worry about ...

[Decsgran in reply to PMRpro]

“But only elderly ladies suffer from it and they aren't significant enough to worry about ...” I think my doctor has that view! In my last telephone appointment with her, I told her my lower back and hips were so stiff and painful that I was having difficulty walking. Her reply was “well you are 77!”

[PMRpro Ambassador in reply to Decsgran]

I got that from my GP - "what do you expect at your age?" At the time I was 51 and at the gym most days!

[Decsgran in reply to PMRpro]

😂😂😂

[Indigo2417 in reply to PMRpro]

Nothing to do with PMR, but I went to my GP having a painful big toe joint. He asked me what my mother’s feet were like. Then said “ Its probably your age”. I was 40 at the time. That’s about as much help as I got.

[PMRpro Ambassador in reply to Indigo2417]

He might have had burning ears if he had tried that on me!! He had a point - there is a genetic component to bunions. But not entirely sure where age came in ...

[Indigo2417 in reply to PMRpro]

I did think at the time - Is this the start of a slippery slope downwards? But I think he was really interested and it was a case of any convenient excuse to get rid of me.

[AtopicGuy in reply to PMRpro]

Now you have some documentary evidence! The idea that PMR burns out in a couple of years seems to originate from the historical reports, before blood tests and steroids were invented. Some of the poor patients, left untreated, got better. All this proved was that PMR is (at least sometimes) an acute disease that could resolve itself in time.

[PMRpro Ambassador in reply to AtopicGuy]

I suspect it derived from a misreading of this paper

pubmed.ncbi.nlm.nih.gov/403...

"The median duration of therapy was 37.3 months. It was estimated that 40 percent of patients will require therapy longer than four years. Corticosteroids were permanently discontinued in 31 patients after a mean of 23.7 months of therapy. The data support the concept of two patient populations--one with limited disease and another requiring long-term therapy. "

Work done LONG after steroids were developed and in fact their 40% of patients needing pred for more than 4 years isn't so far off the figures quoted these days in studies. They picked up the short figure - and conveniently ignored the longer one.

[AtopicGuy in reply to PMRpro]

That's why checking the references to see whether they really support what's written is so important. Peer review should avoid such errors. Reading epidemiological papers is hard work, so it's easy for myths to develop from misinterpretations. Always ask for evidence.

Interestingly, that paper is from 1985, when life expectancies were much lower than now. This could skew the figures either way.

[PMRpro Ambassador in reply to AtopicGuy]

Well why don't YOU start writing to all the rheumatologists to dispute the claims?

[AtopicGuy in reply to PMRpro]

I presume that's sarcasm. Modern medicine is meant to be based on science. "Evidence-based medicine" is the cry. If only!

[PMRpro Ambassador in reply to AtopicGuy]

Not entirely - I have spent the last 12 years bringing things to the attention of research rheumies. But I pick my battles.

[AtopicGuy in reply to PMRpro]

I'm keeping my powder dry, still in the hope that I will get a proper diagnosis and treatment eventually. Then I will make sure those who got it badly wrong are set right. I'm sick of my unusual case being judged against bog standard criteria. And I hate the thought of this continuing to happen to others.

[Animalover65 in reply to PMRpro]

This attitude really shocked me when I was waiting to get diagnosed with PMR. There is a womens equality party. For this attitude to be around in 2024 is awful. Perhaps we need to start a ' wise senior women's party'.

[PMRpro Ambassador in reply to Animalover65]

Given female doctors can sometimes be worse than men ...

[Animalover65 in reply to PMRpro]

Yes a woman nurse practitioner I saw was definately not listening ! Women can take in negative attitudes from society - " interior colonization" the OU call it.

[PMRpro Ambassador in reply to Animalover65]

I think the worst are the women HCPs who have never had period pain!

[Animalover65 in reply to PMRpro]

What is an HCP ?

[PMRpro Ambassador in reply to Animalover65]

Healthcare professional

[Animalover65 in reply to PMRpro]

Ah yes! A bit of empathy would not go amiss. And being able to imagine that someone's experience might be different to theirs!

[PMRpro Ambassador in reply to Animalover65]

Indeed!!!!