Hugh A. Smythe

Unhelpful criteria sets for "diagnosis" and "assessment of severity" of fibromyalgia.

In this issue of The Journal Dr. Wolfe and colleagues introduce 2 new and different protocols (there have been many prior versions) to identify what they call “fibromyalgianess”1,2. In what ways are the new proposals unhelpful? Dilution (the inclusion of milder cases changes prognosis); inconsistency (multiple diagnostic strategies identify different patients); loss of specificity [later criteria sets lose information and fail to discriminate symptoms of rheumatoid arthritis (RA), fibromyalgia (FM), systemic lupus erythematosus (SLE), and osteoarthritis (OA)]; and loss of the ability to recognize FM concurrent with other diseases. Statistical approaches are used that do not make most efficient use of the information available. More fundamental is the continuing distraction from the obligation to accurately identify the origins of pain and choose appropriate treatments3.nnThe odyssey was not without purpose or logic. FM has been described as a spectrum disorder. But there are 2 quite separate spectra. One is a continuous spectrum expressing severity, with FM separated from lesser chronic pain by arbitrary cutpoints. The other is better described as a palette of characteristic symptoms, found to be associated with FM however defined. Many of these statistically significant associations were found in the 1990 Classification Criteria study4. Sleep disturbance, fatigue, morning stiffness > 15 minutes, paresthesias, anxiety, headache, prior depression, irritable bowel syndrome, sicca symptoms, urinary urgency, dysmenorrhea history, and Raynaud’s phenomenon are all listed in Table 6 of the 1990 paper. Because symptoms other than widespread pain were not embedded in the Criteria, the statistical strength of the association of these and other symptoms associated with FM could be tested independent of the 1990 Criteria. Other links were added later, including cognitive problems (“Fibrofog”)5, “dizziness,” jaw pain6,7, and low abdominal pain. If this symptom profile … nnAddress correspondence to Dr. H.A. Smythe, 2 Heathbridge Park, Toronto, Ontario M4G 2Y6, Canada. E-mail: hasmythe{at}rogers.com

Explaining Medically Unexplained Symptoms: Widespread Pain

The symptoms of “fibromyalgia” are due to the interaction between referred pain and amplifying factors.nnGiven that Moldofsky and I described pain amplification related to measurable sleep disturbances1, we yield to no one in recognition of neural factors. Missing from Shleyfer, et al 2 published in a recent issue of The Journal , from 2 commentaries in the current issue3,4, and from the long Wikipedia entry5 is any discussion of referred pain and of tender sites as markers of referred pain. These help identify the underlying somatic pathology, and therefore the necessary treatment and research strategies. Labeling alone doesn’t help; for a full diagnosis, definition of underlying problems and appropriate treatment strategies are required.nnBut there need be no talk of “war” among friends and colleagues (everybody loses wars). Disagreement should be the beginning of creative discussion.nnThe scientific study of referred pain began with the work of J.H. Kellgren6, with whom I had the privilege of working. I quote from a letter I received from him dated May 28, 1999, about 2 years before his death: “...When I started the experimental pain studies in 1936, it was believed that pain was accurately localized in all somatic structures and that only viscera gave referred pain through some special reflex. Our work at that time showed this to be false and led to a clinical method for ascertaining the anatomical source of all pains. This had a big impact on clinical diagnosis in medicine and surgery as well as rheumatology but has recently lost its interest since all the scanners and other machines have taken over....”nnWith great respect, I submit he overstated his case. When I trained, the work of Thomas Lewis and Kellgren was very fresh. We recognized certain features …

Common measures and analytic techniques provide flawed assessments of pain: modeled data, and hip replacement study.

Objective To examine commonly used measures and analytic techniques of pain outcomes, using (1) a synthetic model, and (2) a cohort of patients who underwent total hip replacement. Methods (1) A synthetic data set was constructed with 110 visual analog scale (VAS) values, 10 for each integer from zero to 10. Random noise was added to simulate measurement variations. Drift through time and a therapeutic trial were simulated. (2) Eighty-six patients were studied before and a mean of 17 months after total hip replacement. Assessments included a VAS pain scale, the Western Ontario and McMaster Universities Osteoarthritis Index, Harris Hip Score, and SF-36 scores. Results The clinical study mirrored the model. Correlation coefficients among treatment differences measured by the pain subscales of 4 instruments varied from 0.53 to 0.22. Floor effects obscured benefit. “Percentage improvement” created a directional bias, and had a hyperbolic distribution that invalidated means, variances, and related statistics. The best outcomes were undervalued when postoperative pain measures approached zero. Standardized means enabled pooling of data from the different instruments and facilitated measurement of the variations due to treatment, methods, and subjects, and other factors. Conclusion Outcome measures and analytic techniques are often flawed because of floor and ceiling effects, non-normal distributions, and other problems. Outcomes expressed as “percentage improvement” are inappropriate; changes should be reported in the observed units. Revisions of standard outcome measures to relate pain with activity can better document outcomes, especially favorable results.

Percent Change Was and Is An Embarrassing Mistake

Any fool can predict the future; politicians and investment counselors do it all the time. Modeling past medical and financial events accurately remains a major challenge. Percent change is commonly used in these and other fields of measurement. Quantities in the form of a “percent” are used every day; they are familiar, useful, and generally harmless. But not always.nnProportions as a percent, no problem. “Sixty percent of medical students are female.”nnPercent as a measure of change: “My tax load has increased by 8% in the past year.” No problem so far, but begs the question: 8% of what?nnPercent as a measure of relative change: “The group given “NewDrug™” increased bone density by 5%; 50% more than the group given “OldDrug™.” This is a gross misrepresentation. “Despite recommendations that bone mineral density precision and followup assessment be based upon absolute measurements (in g/cm2), the use of relative change (in percent) is still frequently encountered.”1nnTwo decades ago, I was 60 and my son 30, half my age. Thirty years later he will be 60, having aged 100%. If I survive, I will age only 33%. Clearly, he is aging 300% faster than I. A grandson, who will be 33 years of age at that time, will age 1000% during that same interval. In time I shall stop aging altogether, so they can catch up.nnAre things better in Boston? In the May 6, 2010, issue of the New England Journal of Medicine , a group from the Brigham and Women’s Hospital report on the use of a technology to reduce medication errors. “...units that did not use [the new technology] reported an 11.5% error rate ...versus [a 6.8% error rate] in those that did... — a 41.4% relative reduction”2. (Why not a 4.7% reduction? … nnAddress correspondence to Dr. H.A. Smythe, 2 Heathbridge Park, Toronto, Canada M4G 2Y6. E-mail: hasmythe{at}rogers.com