Sunday, July 5, 2009

How is Rheumatoid Arthritis Diagnosed? Part 1

Why is it so hard to diagnose RA?

Rheumatoid Arthritis is a mystery even to doctors. The diagnosis is a subjective process even though many of the symptoms are clearly measurable. Every book or article I read says that it is difficult to diagnose. Why?

It is only in recent years this disease actually has a name and any identity at all. Rheumatoid Arthritis has never had a single definitive test to prove diagnosis. It was in 1987 that the American College of Rheumatology (ACR) adopted 7 guidelines, created by a committee, which are used in the clinical diagnosis of RA.

While there are seven criteria on the list, rheumatologists may diagnose RA if only four of them are present. They include symmetrical presentation of arthritis; arthritis of the fingers, wrists and hands; positive Rheumatoid factor blood test; morning stiffness; rheumatoid nodules; arthritis in 3 or more places; and radiographic (X-ray) evidence of changes.

Often, clinical guidelines use words like “suggests” or “indicates” diagnosis of Rheumatoid Arthritis. Doctors use these guidelines to decide whether a patient has Rheumatoid Arthritis. Two doctors can decide that a particular patient does have RA even if the criteria are not precisely satisfied.

Why do so many people with Rheumatoid Arthritis go months, and even years before getting an RA diagnosis? I recently met a lady who went to 13 different doctors (including several rheumatologists, I believe!) before finding her RA diagnosis. And, why are so many told they are “atypical”? Why do I meet countless precious people who have RA and are being treated for RA, but do not fit the mold of the 7 guidelines?

I am starting to wonder whether the ACR’s RA mold is getting moldy. It’s getting old already. Things have come a long way since 1987. Consider two things:

First, Medical Advancements:

There are medical tools which were not yet widely available in 1987. There are ultrasound and MRI machines, even small portable ones which can view the inside of the joints. There are also improved CAT scans and bone density scans.

The old Rheumatoid factor (Rf) test was only about 75 % accurate. Many people who are diagnosed with RA do not have a positive Rf. However, a newer test measures another antibody which is present in rheumatoid diseases called the cyclic citrulline-containing peptide. The anti-CCP test is about 90% accurate. There are other antibodies, too. And just recently, the possibility of another new test came over the horizon when another piece to the RA puzzle was found.

There are many other examples of advancements, but these are some which are glaringly obvious and can be understood even by laymen.

Second, the internet:

With the advent of the net, there is a vast amount of evidence about the specific symptoms and indicators of Rheumatoid Arthritis. I know there are a million quacky wacky websites out there. Not that! There are a substantial number of solid legitimate blogs and forums where patients have been documenting the details of their RA. Researchers never had such vast records available to compare and analyze.

A report by the Centers for Disease Control (CDC) found an average of 36 weeks between onset and diagnosis of Rheumatoid Arthritis. That’s nine months. Again, why? They state that “early disease recognition is challenging as only half of those who eventually develop RA initially present with features specific to the condition.”

Do they think there is something wrong with the way that “patients present” or with the diagnostic criteria? Why aren’t the “features with which they present” being considered specific to the condition? Remember, these are not just folks who they bumped into in the elevator; these are patients “who eventually develop RA.” What did they have during the first nine months before the RA diagnosis? Were they RA WANNABES?

The causes of Rheumatoid Arthritis are not known. The cure is not known. Accurate and prompt diagnosis remains elusive. Maybe the patients are correct and the criteria are inadequate.

9 comments:

nygiantsfanatic said...

That 9 month "rule" sounds about right. My diagnosis came right between 8 & 9 months of my symptom on-set.

Kim H said...

You wrote:

"The old Rheumatoid factor (Rf) test was only about 75 % accurate. Many people who are diagnosed with RA do not have a positive Rf. However, a newer test measures another antibody which is present in rheumatoid diseases called the cyclic citrulline-containing peptide. The anti-CCP test is about 90% accurate."

It's crucial that you note the difference between sensitivity and specificity. You are confusing the two here in different tests.

The RF test is not specific to an RA diagnosis (since many people who test positive for RF actually have an autoimmune disease other than RA, and since 10-15% of people who test positive for RF are completely disease-free).

Now, the RF test has a sensitivity of about 70-75%, meaning that about 70-75% of people who have RA will have a positive RF. (About 25-30% of people who have RA will not have a positive RF test.)

The thing that the Anti-CCP test does is increase specificity for RA diagnosis, but not necessarily sensitivity.

What does this mean? It means that if you test positive for Anti-CCP, there's a 90% likelihood that you have RA and not some other autoimmune disease. However, the Anti-CCP test has only slightly higher sensitivity that the RF test; thus, approximately 20% of people living with RA will still test negative for Anti-CCP.

It's confusing, I know. But it's a really important distinction, especially since RA folks who test negative for RF are much more likely to also test negative for Anti-CCP.

HTH

Kim H

mallen said...

I'm still confusing my rheumy. After some visits, he says things like "I don't know" and after others he says "you definately have it". I just wish there was one test I could take that would give me a definate answer. I have had signs of RA for years and after three doctors I finally had a dianogis (sort of).

mereallen on twitter

Kelly said...

Hi Kim,
Thanks for your smart comment. I am sorry if I was unclear. This is a large and complex topic (diagnosis) which I have been studying for a long time. Maybe trying to condense the topic to a single post was not the best decision. I will try to be more specific about both my opinions and the facts when I write How is RA Diagnosed, Part 2. Very briefly, though, I was not suggesting that either test be used alone or even given preference. IMVHO, we ought to use both of them and whatever else can be found. I am glad this blog has such a bright group of readers/commenters which will keep me on my toes. :D

Here’s a link for anyone who wants to read more about the sensitivity / specificity distinction

Kelly said...

Mallen,
You are not alone. Hope you have found a good dr. See you on twitter.

MissDazey said...

I am not smart enough to understand any or all of this. Question, does your treatment depend on which of these tests are taken and the results?

Kelly said...

I am not a dr, Miss D,
but I know that if you have an RA diagnosis, then you should be treated.
If the RA is "aggressive,"
it is my opinion that the treatment should also be aggressive. High results in these tests do often correlate with "aggressive" RA, but it's still not that simple. Your physical condition is the main evidence to the dr. of your RA treatment needs.

Aimee said...

I have had RA symptoms for 2 1/2 years and my official diagnosis is still "indeterminate rheumatism". My Rf and ANA tests are negative, though my sed rate is above normal. Not sure if my doctor tested my anti-CPP back in Jan but I'm going to ask.

My symptoms came on suddenly and severely just after I delivered my twins (my first pregnancy). I thought the pain and stiffness was all in my head until I finally saw my GP after 6 months and he put me on a steroid that made my body feel better than it ever has. I now take Plaquenil and most of my symptoms have subsided except for an occasional flare-up in the hands and sometimes my feet and elbows, and of course, the fatigue.

I'm frustrated with my rheumatologist for not giving me an official diagnosis and am scared that taking the Plaquenil and NSAIDS are going to damage my eyes and liver over time. Or that my arthritis will worsen and become debilitating.

Anyway, thanks for writing this blog. It helps to have all this information and to know you're not alone in this disease.

Kelly said...

Hi Aimee,
Thanks for your comments. I saw your cute pictures. Love the snow!

It does sound like a typical RA pattern, so I am glad you are seeing a rheumatologist. Yes, I agree the meds are scary. For me, I am just more scared of the RA.