The American College of Rheumatology Preliminary Diagnostic Criteria for Fibromyalgia and Measurement of Symptom Severity

Fatigue, cognitive symptoms, and the extent of somatic symptoms became increasingly known and appreciated as key fibromyalgia features.

“the importance of symptoms that had not been considered by the ACR Multicenter Criteria Committee became increasingly known and appreciated as key fibromyalgia features: for example, fatigue, cognitive symptoms, and the extent of somatic symptoms (4 -7).”

• cites [4] 4. Mease P, Arnold LM, Choy EH, Clauw DJ, Crofford L, Glass JM, et al, for the OMERACT Fibromyalgia Working Group. Fibromyalgia syndrome module at OMERACT 9: domain con- struct. J Rheumatol 2009;36:2318 -29. sourcePartly supported

  The Introduction (page not provided) says the 1990 ACR criteria focused on widespread pain and tenderness, while patients also experience fatigue, cognitive dysfunction, and other symptoms. The Cognition section calls dyscognition a salient symptom. The paper does not identify the extent of somatic symptoms as a key feature in the same way, so that part of the claim is not supported. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [5] 5. Choy EH, Arnold LM, Clauw DJ, Crofford LJ, Simon LS, Mar- tin SA, et al. Content and criterion validity of the preliminary core dataset for clinical trials in fibromyalgia syndrome. J Rheumatol 2009;36:2330 -4. sourcePartly supported

  The Introduction (page unavailable) lists fatigue and dyscognition (cognitive dysfunction) among the relevant fibromyalgia domains identified through earlier patient and clinician exercises. It does not identify the extent of somatic symptoms as a domain or establish the claimed progression in recognition of all three features. The Discussion (page unavailable) also says clinical-trial data were insufficient to require dyscognition in the core dataset. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites [6] 6. Mease P. Fibromyalgia syndrome: review of clinical presen- tation, pathogenesis, outcome measures, and treatment. J Rheumatol Suppl 2005;75:6 -21.Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites [7] 7. Mease P, Arnold LM, Bennett R, Boonen A, Buskila D, Car- ville S, et al. Fibromyalgia syndrome. J Rheumatol 2007;34: 1415-25.Not checked — no full text of the source

Approximately 25% of patients considered to have fibromyalgia by their physicians did not satisfy the ACR 1990 classification criteria at the time of the study.

“Approximately 25% of fibromyalgia patients did not satisfy the American College of Rheumatology (ACR) 1990 classification criteria at the time of the study.”

• Also stated in: § Characteristics of patients by fibromyalgia status. · plain

  “Taken as a whole, these data show that approximately 25% of patients considered to have fibromyalgia by their physicians do not satisfy ACR classification criteria for fibromyalgia”

• AssumptionRests on an assumption: The ACR 1990 classification criteria are a valid reference standard for identifying fibromyalgia cases.

The new case definition (WPI >7 AND SS >5) OR (WPI 3-6 AND SS >9) correctly classifies 88.1% of cases classified by the ACR classification criteria.

“This simple clinical case definition of fibromyalgia correctly classifies 88.1% of cases classified by the ACR classification criteria”

• AssumptionRests on an assumption: The ACR 1990 classification criteria are a valid reference standard for identifying fibromyalgia cases.

The most important diagnostic variables for fibromyalgia were the WPI and categorical scales for cognitive symptoms, unrefreshed sleep, fatigue, and number of somatic symptoms.

“The most important diagnostic variables were WPI and categorical scales for cognitive symptoms, unrefreshed sleep, fatigue, and number of somatic symptoms.”

• AssumptionRests on an assumption: Physician diagnosis of fibromyalgia is a valid way to identify fibromyalgia patients for the study.

Removing all muscle variables and the WPI resulted in a misclassification rate of 16.1%.

“Removing all of the muscle variables and the WPI resulted in a misclassification rate of 16.1% (Table 2).”

Using the short variable list, the misclassification rate was 18.4%.

“Using the short variable list (that never contains muscle pain or muscle weakness), the misclassification rate was 18.4%.”

Physician study variables misclassified fibromyalgia cases and controls at rates of 6.2-10.3%, depending on the number of variables in the model and whether the WPI was continuous or categorical.

“Depending on the number of variables in the model (variable group) and whether the WPI was used as a continuous or a categorical variable, physician study variables misclassified fibromyalgia cases and controls at rates of 6.2-10.3%(Table 2).”

For count of patient-endorsed somatic symptoms, physician somatic symptom scale, and SS scale, prior fibromyalgia patients had scores somewhat closer to current fibromyalgia patients than to control subjects.

“However, for the count of patient-endorsed somatic symptoms, the physician somatic symptom scale, and the SS scale, prior fibromyalgia patients had scores that were somewhat closer to current fibromyalgia patients than to control subjects.”

Patients previously diagnosed by clinical criteria were more likely to be classified as prior fibromyalgia (38.3%) compared with patients previously diagnosed by the ACR classification criteria (18.9%; P<0.001).

“Patients previously diagnosed by clinical criteria were more likely to be classified as prior fibromyalgia (38.3%) compared with patients previously diagnosed by the ACR classification criteria (18.9%;P Ͻ 0.001).”

• AssumptionRests on an assumption: The ACR 1990 classification criteria are a valid reference standard for identifying fibromyalgia cases.

The WPI and muscle tenderness were the most important variables in the classification of cases and noncases.

“Figure 2A shows that the WPI and muscle tenderness were the most important variables in the classification of cases and noncases.”

These variables are strongly correlated with the tender point count and the WPI.

“As shown in Table 3, these variables are strongly correlated with the tender point count and the WPI.”

Six categorical rating scale variables had high importance levels: somatic symptoms, waking unrefreshed, cognition, fatigue, sleep problems, and mood.

“From Figure 2B, we identified 6 categorical rating scale variables that had high importance levels (somatic symptoms, waking unrefreshed, cognition, fatigue, sleep problems, and mood).”

Pain intensity was less strongly correlated with the tender point count and WPI (correlation coefficients 0.346 and 0.437, respectively) than the six categorical variables.

“For comparison, pain intensity, with correlation coefficients of 0.346 and 0.437, respectively, was less strongly correlated.”

Irritable bowel syndrome, abdominal pain, and headache added no power to correct classification.

“However, they added no power to correct classification and we did not include them in the diagnostic criteria.”

When applied to study patients using the ACR classification criteria definition of fibromyalgia, the mean SS scale score for prior fibromyalgia was 6.0 ± 2.6.

“When applied to study patients, using the ACR classifi- cation criteria definition of fibromyalgia, the mean Ϯ SD SS scale score for fibromyalgia was 8.0 Ϯ 2.6, for prior fibromyalgia was 6.0 Ϯ 2.6, and for controls was 3.3 Ϯ 2.2 (Table 1).”

Although not a study requirement for enrollment, all of the patients with fibromyalgia diagnosed by physicians had symptoms for at least 3 months.

“Although not a study requirement for enrollment, all of the patients with fibromyalgia diagnosed by physicians had symptoms for at least 3 months.”

A 5-component SS scale that included mood did not perform as well as a 4-component scale.

“In addition, as shown in Table 3, a 5-component SS scale that included mood did not perform as well as a 4-component scale.”

Using the recommended definition, 9.1% of controls would be diagnosed as having fibromyalgia.

“Using this definition, 9.1% of controls would be diagnosed as having fibromyalgia, 53.1% of prior fibromyalgia patients would be diagnosed as having fibromyalgia, and 14.1% of ACR classification criteria-positive cases would not be diagnosed as having fibromyalgia.”

When applied to the ACR classification criteria, correct classification falls to 79.2%.

“When applied to the ACR classification criteria, correct classification falls to 79.2%.”

Mood was correlated with somatic symptoms at 0.621.

“Although we omitted mood, it was correlated with the SS scale at 0.725 and with the components of the SS scale as follows: cognition 0.625, somatic symptoms 0.621, waking unrefreshed 0.619, and fatigue 0.612.”

Of the 315 patients categorized, 42.2% had current fibromyalgia.

“We categorized the 315 patients into 3 groups based on prior diagnosis and current ACR classification criteria status: 42.2% with current fibromyalgia, 13.3% with prior fibromyalgia, and 44.4% who were neither current nor prior fibromyalgia patients.”

Unrefreshed sleep was a better measure than sleep disturbance.

“Unrefreshed sleep was a better measure than sleep disturbance and we recommend its use in the SS scale.”

Mood was correlated with waking unrefreshed at 0.619.

“Although we omitted mood, it was correlated with the SS scale at 0.725 and with the components of the SS scale as follows: cognition 0.625, somatic symptoms 0.621, waking unrefreshed 0.619, and fatigue 0.612.”

96.3% of the patients in the study satisfying the diagnostic criteria had 3 or more tender points.

“However, 98.7% of the patients in the study satisfying the diagnostic criteria had a least 1 tender point and 96.3% had 3 or more tender points.”

Using the ACR classification criteria as the gold standard, the diagnostic criteria diagnose 82.6% of cases correctly.

“using the ACR classification criteria as the gold standard, the diagnostic criteria diagnose 82.6% of cases correctly compared with the clinician's correct diagnosis rate of 84.1%.”

Of the binary variables, irritable bowel syndrome, abdominal pain, and headache had variable importance.

“Of the binary variables, irritable bowel syndrome, abdominal pain, and headache had variable importance.”

The WPI best identified patients diagnosed with the ACR classification criteria.

“The WPI, which strongly correlated with the tender point count and the SS scale, best identified patients diagnosed with the ACR classification criteria.”

Mood was correlated with fatigue at 0.612.

“Although we omitted mood, it was correlated with the SS scale at 0.725 and with the components of the SS scale as follows: cognition 0.625, somatic symptoms 0.621, waking unrefreshed 0.619, and fatigue 0.612.”

Patient data did not work as well in correct classification as physician data.

“Although we collected data directly from patients as well as data from physicians, patient data did not work as well in correct classification as physician data (Table 2).”

Mood was correlated with cognition at 0.625.

“Although we omitted mood, it was correlated with the SS scale at 0.725 and with the components of the SS scale as follows: cognition 0.625, somatic symptoms 0.621, waking unrefreshed 0.619, and fatigue 0.612.”

Results in Table 2 showed little gain from the complete data sets.

“Based on the results in Table 2, which showed little gain from the complete data sets, we collapsed the questionnaire to categorical scales and changed the format to a form that could be used in the clinic.”

When applied to study patients using the ACR classification criteria definition of fibromyalgia, the mean SS scale score for fibromyalgia was 8.0 ± 2.6.

“When applied to study patients, using the ACR classifi- cation criteria definition of fibromyalgia, the mean Ϯ SD SS scale score for fibromyalgia was 8.0 Ϯ 2.6, for prior fibromyalgia was 6.0 Ϯ 2.6, and for controls was 3.3 Ϯ 2.2 (Table 1).”

Using the SS scale score cutoff of ≥7, the mean score for non-fibromyalgia was 2.8 ± 1.4.

“Using the SS scale score cutoff of Ն7, the mean Ϯ SD respective scores were 8.6 Ϯ 1.8 and 2.8 Ϯ 1.4.”

98.7% of the patients in the study satisfying the diagnostic criteria had at least 1 tender point.

“However, 98.7% of the patients in the study satisfying the diagnostic criteria had a least 1 tender point and 96.3% had 3 or more tender points.”

Overall, the fibromyalgia rate among all study subjects would increase from 38.1% to 45.5% using the recommended definition.

“Overall, the fibromyalgia rate among all of the study subjects would increase from 38.1% to 45.5% using the recommended definition.”

The SS scale was strongly correlated with the WPI (0.733).

“The SS scale was strongly correlated with the WPI (0.733) and the tender point count (0.680), and was the strongest correlate of WPI after the tender point count, which was correlated with the WPI at 0.773 (Table 3).”

Using the recommended definition, 14.1% of ACR classification criteria-positive cases would not be diagnosed as having fibromyalgia.

“Using this definition, 9.1% of controls would be diagnosed as having fibromyalgia, 53.1% of prior fibromyalgia patients would be diagnosed as having fibromyalgia, and 14.1% of ACR classification criteria-positive cases would not be diagnosed as having fibromyalgia.”

The SS scale was strongly correlated with the tender point count (0.680).

“The SS scale was strongly correlated with the WPI (0.733) and the tender point count (0.680), and was the strongest correlate of WPI after the tender point count, which was correlated with the WPI at 0.773 (Table 3).”

Using the newly proposed categorical definition for fibromyalgia, the mean SS scale score for non-fibromyalgia was 2.9 ± 1.6.

“Using the newly proposed categorical definition for fibromyalgia, the mean Ϯ SD SS scale score for fibromyalgia was 8.5 Ϯ 2.0, and for non-fibromyalgia was 2.9 Ϯ 1.6.”

The distribution of SS scale scores defines the 3 diagnostic categories.

“As shown in Figure 3, the distribution of SS scale scores defines the 3 diagnostic categories and provides measurement of fibromyalgia symptom severity to patients who do and do not currently satisfy ACR fibromyalgia criteria.”

In sensitivity analyses, unrefreshed sleep provided marginally better differentiating power.

“However, in sensitivity analyses, it provided marginally better differentiating power; we suggest that either scale can be used, although unrefreshed sleep is better.”

In developing new diagnostic criteria, the authors identified 2 variables that best defined fibromyalgia and its symptom spectrum: the WPI and the composite SS scale.

“In developing new diagnostic criteria, we identified 2 variables that best defined fibromyalgia and its symptom spectrum: the WPI and the composite SS scale.”

• AssumptionRests on an assumption: The case definition of fibromyalgia has changed somewhat with increasing recognition of the importance of cognitive problems and somatic symptoms, factors that were not even considered in the 1990 ACR classification criteria.

When applied to study patients using the ACR classification criteria definition of fibromyalgia, the mean SS scale score for controls was 3.3 ± 2.2.

“When applied to study patients, using the ACR classifi- cation criteria definition of fibromyalgia, the mean Ϯ SD SS scale score for fibromyalgia was 8.0 Ϯ 2.6, for prior fibromyalgia was 6.0 Ϯ 2.6, and for controls was 3.3 Ϯ 2.2 (Table 1).”

Using the recommended definition, 53.1% of prior fibromyalgia patients would be diagnosed as having fibromyalgia.

“Using this definition, 9.1% of controls would be diagnosed as having fibromyalgia, 53.1% of prior fibromyalgia patients would be diagnosed as having fibromyalgia, and 14.1% of ACR classification criteria-positive cases would not be diagnosed as having fibromyalgia.”

Using the newly proposed categorical definition for fibromyalgia, the mean SS scale score for fibromyalgia was 8.5 ± 2.0.

“Using the newly proposed categorical definition for fibromyalgia, the mean Ϯ SD SS scale score for fibromyalgia was 8.5 Ϯ 2.0, and for non-fibromyalgia was 2.9 Ϯ 1.6.”

The tender point count was correlated with the WPI at 0.773.

“The SS scale was strongly correlated with the WPI (0.733) and the tender point count (0.680), and was the strongest correlate of WPI after the tender point count, which was correlated with the WPI at 0.773 (Table 3).”

Approximately 25% of diagnosed fibromyalgia patients in both phases of the study did not satisfy the ACR classification criteria, although they were considered to have fibromyalgia by their physicians.

“One of the important findings of the current study was that approximately 25% of diagnosed fibromyalgia patients in both phases of the study did not satisfy the ACR classification criteria, although they were considered to have fibromyalgia by their physicians.”

A severity score ≥7 correctly classifies 92.3% of cases identified by the new diagnostic criteria definition: (WPI ≥7 AND SS ≥5) OR (WPI 3-6 AND SS ≥9).

“A severity score Ն7 correctly classifies 92.3% of cases identified by the new diagnostic criteria definition: (WPI Ն7 AND SS Ն5) OR (WPI 3-6 AND SS Ն9).”

Using the SS scale score cutoff of ≥7, the mean score for fibromyalgia was 8.6 ± 1.8.

“Using the SS scale score cutoff of Ն7, the mean Ϯ SD respective scores were 8.6 Ϯ 1.8 and 2.8 Ϯ 1.4.”

In phase 2, the ACR classification criteria were used in 74.6% of fibromyalgia diagnoses.

“The ACR classification criteria were used in 74.6% of fibromyalgia diagnoses.”

The clinician's correct diagnosis rate was 84.1%.

“using the ACR classification criteria as the gold standard, the diagnostic criteria diagnose 82.6% of cases correctly compared with the clinician's correct diagnosis rate of 84.1%.”

This simple clinical case definition of fibromyalgia correctly classifies 88.1% of cases classified by the ACR classification criteria.

“This simple clinical case definition of fibromyalgia correctly classifies 88.1% of cases classified by the ACR classification criteria, and does not require a physical or tender point examination.”

This simple clinical case definition of fibromyalgia does not require a physical or tender point examination.

“This simple clinical case definition of fibromyalgia correctly classifies 88.1% of cases classified by the ACR classification criteria, and does not require a physical or tender point examination.”

A symptom severity scale score >6 identifies patients satisfying the new diagnostic criteria in 92.3% of cases.

“A symptom severity scale score Ͼ6 identifies patients satisfying the new diagnostic criteria in 92.3% of cases.”

The best misclassification rate obtainable with patient data was 12.7% compared with 6.2% with physician data.

“The best misclassification rate obtainable with patient data was 12.7% compared with 6.2% with physician data.”

The new case definition does not require a physical or tender point examination.

“and does not require a physical or tender point examination”

The SS scale enables assessment of fibromyalgia symptom severity in persons with current or previous fibromyalgia, and in those to whom the criteria have not been applied.

“The SS scale enables assessment of fibromyalgia symptom severity in persons with current or previous fibromyalgia, and in those to whom the criteria have not been applied.”

• Also stated in: § DISCUSSION · plain

  “The SS scale enables assessment of fibromyalgia symptom severity in persons with current or previous fibromyalgia, and in those to whom the criteria have not been applied.”

The proportion of patients who were controls or had prior or current fibromyalgia did not differ between expert physicians and clinical rheumatologists (P=0.640).

“The proportion of patients who were controls or had prior or current fibromyalgia did not differ between the group of 10 expert physicians and the 20 clinical rheumatologists (P ϭ 0.640).”

Patients who improved or whose symptoms and tender points decreased could fail to satisfy the ACR 1990 classification definition.

“Patients who improved or whose symptoms and tender points decreased could fail to satisfy the ACR 1990 classification definition.”

Patients considered to have fibromyalgia by their physicians who did not satisfy ACR criteria appear to have an intermediate severity position between fibromyalgia patients and control subjects, except for somatic symptoms.

“Taken as a whole, these data show that approximately 25% of patients considered to have fibromyalgia by their physicians do not satisfy ACR classification criteria for fibromyalgia, and that they appear to have an intermediate severity position between fibromyalgia patients and control subjects, except for somatic symptoms.”

• AssumptionRests on an assumption: The ACR 1990 classification criteria are a valid reference standard for identifying fibromyalgia cases.
• AssumptionRests on an assumption: Physician diagnosis of fibromyalgia is a valid way to identify fibromyalgia patients for the study.

Misclassification rates obtainable under optimum data mining conditions that do not contain ACR classification criteria-related variables are between 16.1% and 18.4% (14.0% if muscle pain is allowed).

“These data show that misclassification rates obtainable under optimum data mining conditions that do not contain ACR classification criteria-related variables are between 16.1% and 18.4% (14.0% if muscle pain is allowed).”

The distribution of SS scale scores provides measurement of fibromyalgia symptom severity to patients who do and do not currently satisfy ACR fibromyalgia criteria.

“As shown in Figure 3, the distribution of SS scale scores defines the 3 diagnostic categories and provides measurement of fibromyalgia symptom severity to patients who do and do not currently satisfy ACR fibromyalgia criteria.”

Results from phase 2 in Table 5 suggest that the criteria would work satisfactorily in the final format.

“Results from phase 2 in Table 5 suggest that the criteria would work satisfactorily in the final format, which is included in Table 4.”

Loss of a tender point or a painful region for any reason, including improvement, can result in failing to meet classification or diagnostic criteria.

“The loss of a tender point or a painful region for any reason, including improvement, can result in failing to meet classification or diagnostic criteria.”

Neither the ACR classification criteria nor the diagnostic criteria suggested here provide a solution for the classification dilemma of patients who have fibromyalgia but do not meet criteria.

“Neither the ACR classification criteria nor the diagnostic criteria suggested here provide a solution for this classification dilemma.”

• AssumptionRests on an assumption: The central problem in fibromyalgia criteria is the absence of a gold standard or case definition.

Fibromyalgia diagnosis is based on severity assessments.

“It arises because fibromyalgia diagnosis is based on severity assessments.”

The suggested diagnostic criteria create a small discordance between the older ACR classification criteria case definition and the current definition proposed.

“The suggested diagnostic criteria create a small discordance between the older ACR classification criteria case definition and the current definition that we have proposed.”

The SS scale was the strongest correlate of WPI after the tender point count.

“The SS scale was strongly correlated with the WPI (0.733) and the tender point count (0.680), and was the strongest correlate of WPI after the tender point count, which was correlated with the WPI at 0.773 (Table 3).”

The study did not study the performance of these criteria in primary care.

“Although our goal was to develop simple, practical criteria for clinical diagnosis of fibromyalgia that are suitable for use in primary and specialty care, we did not study the performance of these criteria in primary care.”

The difference in classification performance between patient and physician data is related to the fact that it is the physician and not the patient who makes the diagnosis.

“This difference is related to the fact that it is the physician and not the patient who makes the diagnosis.”

The study did not test the criteria among those with other rheumatic conditions.

“We also did not test the criteria among those with other rheumatic conditions, and we recommend that this be done in the future, too.”