Forefeet and the DAS28: a Healthy Dose of Skepticism | Rheumatoid Arthritis Warrior

Forefeet and the DAS28: a Healthy Dose of Skepticism

Study concludes forefoot (toe) joints unnecessary to determine disease activity.

“Forefoot joints were frequently affected on an individual level, but did not significantly improve the measurement range or precision of 28-joint counts in patients with early RA. From a measurement perspective, reduced joint counts are appropriate for use on a population level. The contribution of assessing forefoot joints on an individual level requires further investigation,” Contribution of assessing forefoot joints in early rheumatoid arthritis patients: Insights from item response theory.

The patients studied were part of the Dutch Rheumatoid Arthritis Monitoring (DREAM) remission induction cohort, included from early RA diagnosis. The 459 people with active disease were 62% female and rated their general health as rather low on a visual analogue scale (average of 50 on a scale of 100).

bent toes

Were forefoot (toe) joints affected by RA?

Previous comments by patients about the use of the word forefoot cause me to laugh (which is a good thing actually) now every time I read “forefoot.” Animals we love have forefeet, but the same word is used for the anatomical front part of a human foot: toe joints and the associated bones. Like I always say, this disease teaches patients a lot of anatomy.

Yes. Of the 459 patients, 233 had tender joints in the forefoot, and swelling was detected in 200 patients.

Did it affect the joint counts?

Apparently not. “On average, patients had 6 tender and 7 swollen joints on the 28-joint counts, which increased to 8 tender and 9 swollen joints on the 38-joint counts” using the DAS28, a widely used index of Rheumatoid disease activity or the DAS38 that includes 10 forefeet joints.

Is it reasonable to assume the DAS28 gives an accurate measure of how “active the rheumatoid arthritis is at this moment”?

Not from my perspective.

Some say disease activity may be underestimated when feet are excluded, but this study claims that there is not a significant difference for the average patient. The problem is that the “average patient” is a statistical mean of patients, and a specific patient is not the average patient of course. In adding forefoot joints, the joint count increased by two on average, but it obviously could me more or less in a particular person.

DAS site screenshot

If the issue is what to use for measurement in academic studies, I appreciate the author’s argument that a DAS28 takes less time than a DAS38. However, most studies do take place during actual clinical treatment, and my concern is always for actual patients. There are problems with relying on DAS28.

  1. Commonly affected joints, such as cervical spine, affected early in the disease over 80% of the time, are not included in DAS28 or any standard measure of disease activity.
  2. Systemic symptoms (including common ones such as fever, fatigue, anemia, and Sjögren’s syndrome) are not included either.
  3. Conspicuous swelling has been shown to be an inaccurate estimate of joint activity, when compared with data from musculoskeletal ultrasound.
  4. Joint counts are not usually done in most clinics anyway, nor are other outcome measures.

Easy peasy – not so much…

It sounds simple enough: “Just assess the number of swollen and tender joints and measure the ESR.” But living with Rheumatoid disease – or reading about it here on RAW – you know better. You know people fall through the cracks because this disease is not really a “a type of arthritis.” You know that Rheumatoid disease doesn’t care that there are no joints in the lungs or the eyes, and that the disease doesn’t always start in the hands.

Each foot contains 33 joints. No matter how many times I read the paragraphs about the statistical methods used by these investigators, I’m skeptical that by including only 28 joints of the entire body, we get an accurate assessment of disease activity.

Recommended reading

Kelly O'Neill Young

Kelly O'Neill (formerly Kelly Young) has worked over 10 years as an advocate helping patients to be better informed and have a greater voice in their healthcare. She is the author of the best-selling book Rheumatoid Arthritis Unmasked: 10 Dangers of Rheumatoid Disease. Kelly received national acknowledgement with the 2011 WebMD Health Hero award. She is the president of the Rheumatoid Patient Foundation. Through her writing and speaking, she builds a more accurate awareness of rheumatoid disease (RD) aka rheumatoid arthritis (RA) geared toward the public and medical community; creates ways to empower patients to advocate for improved diagnosis and treatment; and brings recognition and visibility to the RA patient journey. In addition to RA Warrior, she writes periodically for newsletters, magazines, and websites. There are over 60,000 connections of her highly interactive Facebook page. You can also connect with Kelly by on Twitter or YouTube, or LinkedIn. She created the hashtag: #rheum. Kelly is a mother of five, longtime home-schooler, NASA enthusiast, and NFL fan. She has lived over thirteen years with unrelenting RD. See also https:/rawarrior.com/kelly-young-press/

29 thoughts on “Forefeet and the DAS28: a Healthy Dose of Skepticism

  • April 2, 2013 at 5:06 pm
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    rawarrior Great article and couldn’t agree more! It all seems to be about the convenience of collecting data to make life easier for medics

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  • April 2, 2013 at 6:00 pm
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    How do you NOT calculate an area that is known to potentially have disease and contribute to deformity or disability??

    An analogy can be drawn with breast cancer. Let’s say breast cancer cells have migrated to the lymph glands. Obviously, anatomically this is outside the region of the breast, so if breast cancer metastisizes to other regions, it doesn’t count ? We just ignore it ?? Um……

    What is THE POINT of this decision ???

    I am continually astounded at the lack of logical thinking or common sense in rheumatology.

    Reply
    • April 2, 2013 at 6:19 pm
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      Yes, that’s the same question I asked recently in the title of a blog: what if they only treated the cancer in Dave’s kidneys? It was stage IV RCC – it was in his lung, leg, tongue, – I can’t remember where else..
      If you read their statistical analysis, they believe they find enough without actually taking off shoes & examining toes. I’ll paste below. I do appreciate statistical significance in research, but there does come a point when this is too much hocus pocus & I want to see the trees no matter how pretty the forest is.
      And the author is careful to acknowledge that in “individual patients” it may still have value & that should be studied more.

      Statistical methods.
      To analyze the contribution of the forefoot joints, an IRT model (the generalized partial credit model [GPCM]) (14) was applied. Both the 28- and 38-joint counts of tenderness and swelling had to fit the GPCM before the contribution of the forefoot joints could be analyzed. This fit was analyzed with Lagrange Multiplier Q1 tests (15), where absolute effect sizes of <0.10 were seen as an indication of good item-model fit (16, 17).

      Next, the reliability and corresponding measurement precision of the joint counts with and without forefoot joints were evaluated and compared. IRT global reliability is equivalent to Cronbach's alpha, but based on IRT scores (theta) instead of raw scores (18). The theta scores are scaled at approximately 0 and correspond to the degree of joint tenderness or swelling a patient experiences. Reliabilities of >0.7 were considered sufficient for group use, whereas values of >0.85 were deemed necessary for individual use (19).

      Local reliability and measurement precision of both the total joint counts as well as their individual joints were derived from 2 types of information curves (18, 20). First, the test information curves (TICs) were investigated to determine the range on the underlying scale where the total joint counts can reliably (precisely) measure a patient’s degree of joint tenderness or swelling, where reliability = 1 − (1/test information at θ) and the precision of the estimated theta is the reciprocal of the test information (Var(θ) = 1/test information at θ) (18). TICs of joint counts with and without forefoot joints were compared to determine the effect of including forefoot joints on the measurement precision and measurement range of the total instrument. A TIC is a sum of the individual item information curves (IICs). These show the contribution of the individual joints to the estimation of joint tenderness or swelling. IICs of the forefoot joints were compared to the IICs of the other joints to determine their individual contribution to the total instrument and to evaluate for which patients they provide the most information.

      Finally, the alignment between the patient and the joint distributions was evaluated. Ideally, the mean scores of these distributions should be relatively close to each other and the distributions should approximately cover the same range of the scale. Joints measuring outside the range of the patient distribution are less informative about the patients’ joint tenderness or swelling than joints measuring inside this range.

      IRT analyses were performed with the statistical program MIRT (21). Full item parameter calibrations are available from the corresponding author upon request. Patient and joint distributions were plotted with SPSS, version 18.0.

      Reply
  • April 2, 2013 at 6:04 pm
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    I am literally walking on the tops of my toes. I had surgery for hammertoes on both feet. Pins in one and screws in the other and they all came out and my feet went right back to the way they were. I think joints have a mind of their own.

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  • April 2, 2013 at 6:08 pm
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    Great post Kelly! One of the first joints that were affected by my RA were my foot joints bilaterally. My rheum discounted my foot pain as not a part of my RA….I was in totall agony…I was forced to crawl to the bathroom on my hands and knees because it became too painful to walk…I finally ended up in the ER in total pain and they gave me a steroid injection and a steroid burst with taper. My rheum was very angry at that, and said they were wrong to assume that the pain in my feet was due to my RA. I requested a referral to a podiatrist..AND…It was not until I visited that podiatrist that I learned the truth about RA and the feet! He is a young and newly trained podiatrist and is very informed and articulate in his description of RA. He told me that RA of the feet usually does not have much swelling and is often overlooked by rheum docs. He noted the minor swelling that my rheum never mentioned and I never knew was there. He also told me my metatarsal pain was being referred from the subtalar joint which was painful and swollen along with an adjacent synovial cyst tht had formed due to chronic inflammation…he said if this inflammation was allowed to continue, the bones in my feet would eventually collapse. My rheum at the time, due to the podiatry report, began biologics…finally….RA in the feet…is a BIG deal…our feet support our whole body..without our feet? We cannot walk…and crawling is not an option and shouldn’t have to be for any of us!

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    • April 2, 2013 at 6:18 pm
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      My podiatrist was the first one to believe I had it too. And the first to not be dismissive of my symptoms. Like you, I was literally crawling some days.

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    • April 2, 2013 at 6:23 pm
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      Excellent post Susan. Thank you.

      Reply
  • April 2, 2013 at 6:43 pm
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    It’s interesting how much arthritis exams have changed, even in the 30+ years since I’ve been diagnosed. Up until about 1995 I was having joint by joint exams at each visit, with each change carefully put in my chart.

    Today I get my hands examined, and my other joints poked and prodded through my clothes while the dr. chats, nothing like the thorough exams they used to do. My doc jots down a sentence, then discusses my meds and anxiety / depression / and other types of issues which I don’t think are nearly as important as joint by joint exams.

    I think it doesn’t fit patient perspectives to take out forefoot exams to see activity level… most patients DO have active disease in those areas, and I at least feel it is indicative of the overall disease, even just in terms of inflammation / pain, not necessarily deformity.

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  • April 2, 2013 at 9:32 pm
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    I just saw my rheum doctor today. 3 months on Enbrel and the only major pain left in my body is my feet. Periodically my ankles and wrists so I have improved dramatically until last week when my hips started bothering me. She thought it was Fibromyalgia in the hips. Everything is always Fibromyalgia when I have no swelling. Because I have no swelling in my feet she decided it was Osteo. It is RD in my feet. My hips are most likely RD. I have sharp stabbing pain when I walk like I do in my feet, ankles hands and wrists -like having broken bones. It is very frustrating.

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  • April 2, 2013 at 9:49 pm
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    I have feet that don’t do things consistently. When the joints that connect the toe to the foot, feels like they are right under the ball of the foot (and I forgot their name) hurt, they are worse than a kidney stone, worse than my hands have ever been, and possibly worse than a toothache. Luckily for me, they are pretty intermittent and seem to hurt once every few weeks at most. When I get up and it feels like I stepped on a knife, I hurry and put my birkenstocks on, take my meds and wait a bit for some pain relief before trying to do things like take a shower.

    The scores and reports of pain, etc. can vary widely depending on whether or not my feet have decided to speak up that day.

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  • April 2, 2013 at 10:59 pm
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    My feet hadn’t bothered me since early in my RA diagnosis, but recently, since I have been in a non-stop flare, my feet are killing me! Every step I take is painful. Where my toes meet my feet, I feel like I am walking on marbles and I also have severe sharp plantar fasciitis type pain in my heels and arches and sometimes ankles. As noted in one of the other comments above, I know definitively that this is all part of the RA flare. So is my eye inflammation, and the sacroiliac pain, and fatigue, and and….
    I am actually fine with my rheumatologist not doing a complete physical exam every visit. She has known me for 10 years, and she completely takes me at my word as to what has been hurting and how I am feeling, and I like that.

    Reply
  • April 2, 2013 at 11:24 pm
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    Kelly, My first symptoms were in my feet and my feet are the first thing to start hurting when I have a flare. The funny thing is your post made me realize that my rheumatologist will check my feet if I am wearing flip flops but doesn’t bother if I am wearing sneakers and socks. Hmmm….will have to ask her what that’s all about at my next visit!

    Reply
    • April 2, 2013 at 11:27 pm
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      I’ve heard diabetes patients advised to take their shoes off each time while waiting for the doctor. It may be for different reasons, but maybe that would help with some doctors who count joints.

      Reply
  • April 3, 2013 at 1:19 am
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    I had to muffle some laughter because my kid is snoozing – I was doing some writing and I wanted a synonym for absurd, so I pulled up thesaurus.com. I picked the word asinine. I stopped writing twenty minutes ago but the tab was open as I got on this site. So perfect.

    Rheumatologists are an odd and stubborn bunch, to generalize. It would be one thing if doctors would say “Yeah, this is a shortened form to save time, I’ve seen a thousand patients with damage to joints in the foot, will take the socks off briefly to see how it’s going.” But there is a decent chance the abbreviated form will reduce access to treatment for some people based on a study that should be taken as grain of salt.

    Oy!

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  • April 3, 2013 at 1:53 am
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    My RA started in my feet, namely toe area. It ate away joints in 8 of my toes. I had to have them fused. I had and have unbearable pain in my feet, which are the most affected and also my hands and lower back are flaring up now.

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  • April 3, 2013 at 9:00 am
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    > The problem is that the “average patient” is a
    > statistical mean of patients, and a specific patient
    > is not the average patient

    Absolutely! I used to say that the average person has one ovary! Statistically true, but it gives you no useful information about any individual.

    I haven’t read the study (nor even studied this post) but I’ll ask: ded the researchers publish the raw data so we can assess it and look for other patterns? I know that’s not common but it’s core to helping improve how well science aligns with patients’ needs (and even with how science itself should work).

    p.s. Ruder people can have lots of fun with my “one ovary” thing by applying it to an *assortment* of body parts between the genders. But I won’t go there. 🙂

    Reply
    • April 3, 2013 at 10:49 am
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      Hi Dave,

      I am a researcher (on disability now) so am also interested in the raw data of this study.

      What I find intriguing is that if the research question is about the difference in accuracy when including or excluding forefeet and the instrument being used for comparison is the DAS 28 as the benchmark, we’re already starting with a faulty research design.

      Sufficient research has already “proven” that the reliability of joint counts (DAS 28) is not as accurate as data obtained from power doppler ultrasound or MRI. So, if we start with the DAS 28, we’re already starting with a measure that doesn’t accurately report synovitis, hypermia, or bone erosion of the joints.

      If I’m understanding this study correctly, the inadvertent effect of the conclusion is to further reduce data that is obtained about rheumatoid disease activity. I understand that the purpose of the study MIGHT be to determine the most expedient method to obtain accurate information about disease activity. Unfortunately, this study seems to have such a faulty design that it harms rather than helps the field of rheumatology.

      Reply
      • April 3, 2013 at 11:36 pm
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        Hi Helen, I’ll send you some more information on this by email. Another idea is to write to the author – the public email is always posted on the author information tab if it’s not already on the title page. I’d ask the author some of your specific questions. Hopefully she will correspond with you.

        Reply
  • April 3, 2013 at 9:28 am
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    Kelly,
    I sent you a photo of one of my feet recently. My feet were the first to br affected. I was walking on such huge nodules the size of golf balls. I have had surgeries where there are few bones left & my toes are crowding. I need more surgery & my surgeon said with the huge nodules on my big toe I would have to sign a statement he may have to cut part of my toe off. Naturally I can’t take that chance since that is the toe that gives you balance. My feet are so far gone I feel there is no hope. I wear tennis shoes everywhere that are 2 sizes too big so I can fit my orthotics in them. I have constant pain in my feet. I am appalled that they would not consider joints in your feet. Hands & feet are the first affected & mine have paid the price of running out of options for any relief.

    Reply
  • April 3, 2013 at 10:01 am
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    My feet were the main reason that I was diagnosed with RA. The pain was unbearable for the long term. Now I have had the forefoot (bones near the toes) reconstructed three times because once it didn’t work.
    Though doctors don’t go out of their way to use this term anymore the forefoot reconstruction is considered “salvage surgery”. The heads of my metatarsal bones are gone so I don’t get the walking on marbles feeling anymore.

    I have a good orthotist and with the orthotics and an ankle brace my gait can look pretty normal.
    So in my case there is not much to be gained by checking toe joints, but the RA does progress through the foot to the midfoot and then to hindfoot. When it hits the hindfoot it can seem that you have pain in the ankle but it is really lower down in the little bones below and in front of the ankle.

    I am actually shocked to hear that there are rheumatologists out there who will deny that foot pain is RA.

    Reply
  • April 3, 2013 at 2:11 pm
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    Here are a few of the links to the research studies mentioned in Kelly’s two posts about inclusion of the forefoot in monitoring disease activity and progression.

    I cannot access the full journal article by Siemons et al (2013). but from what I can find, I think the study is based on the original research by van Tuly et al. (2012):

    van Tuly (2012) Remission in early rheumatoid arthritis defined by
    28 joint counts: limited consequences of residual disease activity in the forefeet on outcome. Annals of Rheumatic Diseases, 71:33–37. doi:10.1136/ard.2011.153742

    http://ard.bmj.com/content/71/1/33.full.pdf+html

    Yazici (2013) Tools for monitoring remission in rheumatoid arthritis: any will do, let’s just pick one and start measuring. Arthritis Research & Therapy, 15, 104 doi:10.1186/ar4139

    http://arthritis-research.com/content/pdf/ar4139.pdf
    http://arthritis-research.com/content/15/1/104

    Reply
  • April 5, 2013 at 4:47 am
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    My feet were not a problem for me at first. My knees, hips and hands were affected at first. RD later moved to my feet. If the RD had stayed out of my feet, I would not be as disabled. I can walk a little bit, then my feet start to swell, and then my feet are just a mess. I have only been at this a couple of years, and some of these posts are scary.
    These studies don’t make any sense. If I can’t walk, them aren’t I more disabled? I am now using wheelchairs and scooters in some situations. It is just awful!

    Reply
  • April 28, 2013 at 8:53 pm
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    Forgive me if I mentioned this on here before, but, my rheumy asked for x-rays of my feet a few weeks back. “Why my feet?” I mean, they are bad, but not nearly as bad as my hands or lower spine. She told me that radiological changes often show up earliest in your feet with RA, even though the symptoms don’t always seem as severe in that area.

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    • April 28, 2013 at 9:50 pm
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      I’ve never heard of that, Rae. Most rheumatologists are focused on the hands because of their training. It is highly individual which joints are most affected and in what order. The best thing is for you and your doc to communicate and test the joints that are most affected, whenever you both decide tests are needed.

      Reply
  • August 15, 2013 at 4:46 pm
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    As a statistician with RA that initially presented in my feet, I’m definitely going to take a closer look at their methods. And I agree with the prior comment about how counter-intuitive it is push for less information and data when making a diagnosis or tracking a patient’s progress.

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    • August 15, 2013 at 5:09 pm
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      Great, I’m curious to see what you come up with. We have a few statisticians on our team so let me know.
      my feet: age 15
      my hands: age 40 (with no visible swelling until age 42)

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  • August 15, 2013 at 7:18 pm
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    OMG, those foot joints were one of the first things that caused me pain, the swelling was apparent to my PCP doctor when I first diagnosed myself, and those joints are the reason I have been unable to walk very far without great pain and limping. That they would not count those joints is criminal!

    Reply
  • August 30, 2013 at 4:04 pm
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    Feet were my first symptom at 19. I am just now being diagnosed at 47.
    I went the the infirmary at university and the doctor said it could be tendonitis or perhaps I’d fractured a metatarsal, which would heal on its own. Both feet mind you. Then it disappeared and didn’t come back until last year. And I thought oh, this feels familiar. And of course I had different symptoms in the interim.
    I’m feeling rather bitter about my experience with the medical establishment. Hopefully the rheum I am waiting to see will be good. Fingers crossed. It’s the rheum clinic at a major university that is also associated with a research foundation with lots of trials.

    Reply

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