Applying the Pareto Principle (80/20 Rule) to Rheumatology

Paul SufkaEducation

“If you can’t explain it to a six year old, you don’t understand it yourself.” ― Albert Einstein

Update 1/4/2013: This post was republished today in the ACP Internist blog

Since entering the field of rheumatology, I have too frequently heard comments from clinicians admitting their lack of knowledge and understanding in the field of rheumatology.

I understand why rheumatology has gotten a reputation as being difficult. The basis for the understanding of rheumatic conditions is the immune system, where our knowledge is becoming ever complex. Many of the rheumatic conditions are uncommon, so clinicians are less comfortable recognizing and treating them. To make things worse, we order a number of oddly named antibodies and use medications that affect the immune system in strange ways.

Fortunately, the basics of rheumatology are not extremely difficult to understand.

The Pareto Principle (80/20 rule)

The Pareto Principle says that 80% of the results come from 20% of the effort, knowledge, or resources. This rule has been shown effective  in numerous fields outside of medicine, especially business and finance, and can be used as an effective technique to approach any difficult topic.

With this in mind, I’ll try to focus on the 20% of rheumatology that I think is the most high yield for those outside of rheumatology to understand.

(Sorry fellow rheumatologists, this post isn’t intended to teach you much of anything, but might be helpful when you give guidance or mentor others. I would GREATLY appreciate any additions or corrections in the comments section below).

The unifying mechanism in the rheumatologic diseases is inflammation

Recognition of inflammation is really the first step in thinking about the rheumatologic diseases. With few exceptions, the first thing I’m trying to decide with every new patient I see in the office is whether an inflammatory condition is present, or not.

Recognition of inflammation goes back to the very basics of what we are taught in medicine: the history and physical exam

Joint pain is an extremely common complaint. Being able to differentiate inflammatory from non-inflammatory joint pain is likely the most high yield knowledge in rheumatology. Differentiating these two processes is important because the treatment strategy will vary greatly between the two types.

Taking a pain history: OPQRST

Many of us are taught early in our training the mnemonic “OPQRST” to remember the components of a taking a history. While likely very basic, this is worth reviewing, as details discovered here can greatly change suspicion for inflammation later on.

  • Onset – When did the symptoms start? Rapid or slow onset?
  • Provoking/palliating factors – How are the symptoms affected by use? What about rest? Do anti-inflammatories or other medications help? What else have they tried?
  • Quality (description) of the pain – Dull, aching, stiffness, burning, etc?
  • Regions/radiation – What joints or other areas are involved? (Remember to ask about the neck and back) Does the pain radiate from one area to another?
  • Severity – Generally rated on a scale of 0-10
  • Timing – Constant or intermittent symptoms? Does it change throughout the day (morning stiffness)?

In terms of differentiating inflammatory from non-inflammatory causes, the most helpful are the provoking/palliating factors, and the timing of the symptoms. Inflammatory arthritis is typically associated with pain that is worst in the morning or after resting, with stiffness typically lasting 30-60 minutes or more, and improves with activity.

The complete review of systems: finding the puzzle pieces

The next most powerful tool that rheumatologists use is the complete review of systems. Lack of comfort with what questions to ask,  or the feeling that this takes too much time, is likely another reason that many clinicians are uncomfortable with rheumatology. In reality, the puzzle pieces found in the complete review of systems is often where the bigger picture starts to come into place. Feeling overwhelmed? Use the patient as a guide, starting head to toe, to help remember features to ask. Use a checklist if needed at first, or consider using this rheumatologic patient history form from the ACR.

The cardinal signs of inflammation on exam: if you don’t know what to look for, you won’t find it

Most of us are aware of the five cardinal signs of inflammation, but might not have been taught some of the details to look for:

  1. Dolor (tenderness on palpation)
  2. Calor (heat): The joint is typically cooler than the surrounding tissues.
  3. Rubor (redness/erythema)
  4. Functio laesa (loss of function): Typically decreased ROM due to tenderness. If joint function is normal, consider surrounding tissues as the cause of pain. This can be particularly helpful in differentiating cellulitis and/or bursitis from joint inflammation and septic joints.
  5. Tumor (swelling):
  • Look for loss of “dimples” around the joint & decreased skin lines over the joint
  • Feel for the edges of the joint to feel “boggy/squishy” or less distinct
  • Feel small joint swelling/effusions by pushing with one finger & sensing with the other

The Rheumatology Image Bank, especially comparing images of rheumatoid arthritis and osteoarthritis is great resource to look further at these details.

A more detailed resource for rheumatologic exam tips can be found here:

Palpating joint inflammation: practice, practice, practice!

With enough practice, you can learn to palpate synovitis (I have taught medical residents to do this in clinic over the course of a morning). Practice palpating your own joints (assuming they are normal), especially the hands. You typically should easily be able to feel the edges of the joint lines, with only the sense of a normal, thin layer of skin separating the joints from your fingers. If you feel boggy/squishy or less distinct joint lines, along with other features from above, inflammation is more likely.

When to order an ANA

This article: Cleveland Clinic Journal of Medicine 2002; 69(2):143-146 (full text and pdf available without subscription) is a great review of when to order an ANA for our patients.

In summary an ANA should be ordered when the pretest odds of autoimmune disease are high, which is based on findings from our history and physical, summarized  in the table below:

Rheumatoid factor (RF): consider causes other than rheumatoid arthritis

Similar to the ANA, the RF should be ordered when the pretest odds of rheumatoid arthritis are high, which requires joint inflammation/synovitis to be present, and increases with the number of affected joints (refer to this excerpt from the 2010 ACR/EULAR RA Classification Criteria for Rheumatoid Arthritis; see also: link to complete pdf article). When suspicion of rheumatoid arthritis is high, typically an anti-CCP is also ordered.

Keep in mind that a positive RF is common in a number of other rheumatic disorders (Sjogren’s syndrome and cryoglobulinemia being most common, but the other connective tissue diseases such as lupus to lesser degrees).

The most common other condition that causes a positive RF is hepatitis C infection, which must be ruled out when a positive RF is detected (additionally, hepatitis C infection is associated with an inflammatory arthritis).

Other conditions associated with positive RF include hepatitis B, lymphoproliferative disorders, malignancy, chronic infections, inflammatory lung conditions.

Common mistakes in gout management

When I asked for suggestions for high yield rheumatology topics on Twitter, gout quickly came up multiple times. Since the incidence of gout is on the rise, likely related to increased risk factors (obesity, diabetes, chronic kidney disease, cardiovascular disease, and hypertension), knowledge of appropriate management will only become more important.

Gout management is divided into acute management (typically treated with prednisone; colchicine, or NSAIDs) and management of hyperuricemia.

The management of hyperuricemia is where most errors in management occur, especially failure to lower the uric acid to 6.0 or less. In most patients, this is accomplished by titrating the allopurinol dose every few weeks until this is achieved, and many clinicians fail by never titrating to a high enough dose to reach this goal. Additionally, most patients are placed on prophylaxis against attacks when first initiating medications to lower uric acid, since risk of flare is highest during this time. These topics are covered nicely in a two part update, published in October 2012.

In closing, I hope this serves as a good starting point for clinicians to become more comfortable in the field of rheumatology. I invite my rheumatology colleagues to post additions, corrections, and any comments below.