Research Review By Dr. Ceara Higgins©

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Date Posted:

November 2019

Study Title:

Fibromyalgia and myofascial pain syndrome: Two sides of the same coin? A scoping review to determine the lexicon of the current diagnostic criteria

Authors:

Bourgaize S, Janjua I, Murnaghan K, Mior S, Srbely J & Newton G

Author's Affiliations:

Department of Human Health and Nutritional Sciences, University of Guelph, ON, Canada; Canadian Memorial Chiropractic College, Toronto, Canada.

Publication Information:

Musculoskeletal Care 2019; 17: 3-12.

Background Information:

Fibromyalgia (FM) and myofascial pain syndrome (MPS) are both commonly diagnosed forms of chronic musculoskeletal pain and in some ways are clinically comparable (1). The prevalence of FM is estimated at 1.7-5.4% in the general population (2), while MPS ranges from 30-85% in clinical populations (1).

FM is defined by widespread, chronic musculoskeletal pain with the presence of palpable tender points (TPs – distinct areas of soft tissue which are painful under palpatory pressure of less than 4 kg, but otherwise indistinguishable from surrounding tissue) (1). MPS, on the other hand, is defined by regional muscle pain associated with abnormalities in both motor and sensory function, and the presence of myofascial trigger points (MTrPs – hyperirritable spot/nodules within a taut band of skeletal muscle, patient pain recognition and painful limitation in ROM [note twitch response and predicted pain referral pattern are no longer required]) (1). Because these conditions are clinically similar, MPS is commonly misdiagnosed as FM. Improper diagnosis can lead to unnecessary medical tests and referrals, a lack of improvement in symptoms, prolonged time to reach an accurate diagnosis, patient frustration and increased burden on the healthcare system (4). Misdiagnosis is largely attributed to similarities in clinical presentation between MTrPs and TPs, a lack of reliable laboratory tests and the potential co-morbidity of FM with MPS. The overlapping lexicon used to describe the clinical manifestation and diagnostic criteria for these conditions may also be a significant source of confusion.

The purpose of this scoping review was to determine the current lexicon of diagnostic criteria used to diagnose FM and MPS in published studies. The authors further aimed to identify any potential inconsistencies in diagnostic terminology to contribute to the development of a standardized vocabulary for the diagnosis of FM and MPS, which would hopefully promote consistency across both clinical and research settings.

Pertinent Results:

Literature Search Results:
After screening over 5000 papers, 493 articles were included in the analysis. Of these, 410 (83.2%) were related to FM, and 83 (16.8%) looked at MPS. Of these, 21 (5.1%) of the FM articles and 10 (12%) of the MPS articles did not state the use of diagnostic criteria, instead recruiting pre-diagnosed subjects.

Diagnostic Criteria:
The American College of Rheumatology (ACR) criteria for the diagnosis of FM was first developed in 1990 and is the most widely accepted and implemented criteria (1990 criteria: widespread pain for > 3 months, pain on both sides of the body and above/below the waist, axial pain and at least 11/18 tender points on palpation). 81.7% of the articles on FM applied the ACR 1990 criteria. A further 4.6% used the ACR 2010 criteria, 0.2% used the ACR 2011 criteria, 2% used both the 1990 and 2010 ACR criteria, and 0.5% used the 1990, 2010, and 2011 ACR criteria (2010/2011 criteria: symptoms > 3 months, addition of Widespread Pain Index and Symptoms Severity requirements, patient does not have a disorder that otherwise explains their pain). Finally, 1.5% used the ACR criteria, but failed to specify which version and 0.7% used their own unique criteria. Overall, it was found that the individual criteria used in the published literature were consistent. In addition to these criteria, several different pain rating scales, durations of symptoms, and recruitment methods were used across the included studies. These included the visual analog scale (VAS), verbal numeric scale, myalgic score, FM impact questionnaire score for pain, symptomatic durations of longer than 6 months/> 1-year/18 months/ and recruitment through telephone screening, patient self-diagnosis, patient interview, newspaper advertisements, support groups and hospital department referrals. All of these were used in varying combinations with each other.

The most commonly utilized set of criteria for the diagnosis of MPS is The Trigger Point Manual (Simons, Travell and Simons, 1999), with 32.5% of articles directly citing this as their primary diagnostic framework and an additional 33.7% indirectly mentioning the use of that manual. 8.4% of the articles used additional sources of published literature. This may be due to a lack of knowledge regarding the manual or to the lack of a gold standard diagnostic criteria for MPS (3). The combinations of criteria used in the diagnosis of MPS were found to be significantly less consistent than those used for FM, with The Trigger Point Manual using diagnostic criteria based on the identification of MTrPs combined with other physical examination findings, including a regional pain complaint, restricted range of motion and referred pain. As well, several other pain rating scales (including the VAS, Brief Pain Inventory, and an ordinal self-rating pain scale), seven different symptomatic durations, and 15 additional physical findings were all used in the diagnosis of MPS.

Clinical Application & Conclusions:

Generally speaking, a wider range of diagnostic criteria was used for the diagnosis of myofascial pain syndrome (MPS) in the literature compared to fibromyalgia (FM). This may partly explain the lack of reliability pertaining to the diagnosis of MPS. MTrPs are generally seen as the defining characteristic of MPS; however, there is currently no gold standard (ex. EMG, ultrasound, biomarkers etc.) for identifying MTrPs other than palpation of a tender spot/nodule in a taut band, patient pain recognition and painful limitation in range of motion. In addition, MTrPs are clinically associated with a wider range of medical conditions. Therefore, the identification of MTrPs cannot be assumed to be consistent across practitioners (evidence for reproducibility of MTrPs identification via palpation is moderate at best) or to be specific to MPS. In contrast, the criteria for the diagnosis of FM are more widely known and accepted due to extensive study and acceptable reliability.

Overlap in the diagnosis between FM and MPS can also be attributed to similarities in their tenderness profiles and an inability to reliably differentiate TPs and MTrPs (5). Another common area of overlap includes symptom duration, with MPS commonly described as including pain lasting > 3 months and the ACR 1990 criteria for FM also using a symptom duration of > 3 months. As well, although MPS is generally considered to involve regional pain, it can also present as widespread pain, making this differential diagnosis even more difficult.

More research is needed on the proper distinction between FM and MPS. As well, a gold standard for the diagnosis of MPS needs to be developed with proper research to determine reliability and validity of the diagnostic criteria. Finally, future research should aim to develop a standardized vocabulary within the diagnostic criteria for FM and MPS in order to avoid confusion and aid in consistency of diagnosis for patients with chronic musculoskeletal pain.

EDITOR’S COMMENT: The differentiation between FM and MPS can certainly be challenging in clinical practice and to some degree, this distinction may not ultimately impact chiropractic clinical management too much. Having said that, the search for differentiating factors is still worthwhile and can directly inform not only the diagnosis we convey, but also the language we use to describe these conditions – which can certainly impact not only immediate responses to care, but also long-term prognosis. Every patient is different and it remains prudent to approach everyone as an individual, particularly when chronic pain of this nature has developed.

Study Methods:

The authors performed a rigorous literature search, adhering to the PRISMA four-phase flow diagram guidelines. However, no formal quality assessment was performed (hence this was labeled as a ‘scoping’ review versus a ‘systematic’ review). PubMed, MEDLINE, CINAHL, Cochrane, and Index to Chiropractic Literature were searched from Jan 1st, 1997 to May 12th, 2017 using the following inclusion criteria:
  • Study of an intervention
  • Published in English in the last 20 years
  • Investigated patients with musculoskeletal pain
  • Applied criteria in the assessment of musculoskeletal pain, resulting in the diagnosis of FM or MPS
  • Intervention studies could employ the following methodologies: pre-post study design, nonrandomized, randomized control trial, quasi-experiment or crossover if they employed symptomatic patients presenting with either FM or MPS
Articles were excluded based on the following:
  • Methodology/structure: guidelines, editorials, letters, commentaries, unpublished manuscripts, dissertations, government reports, books, conference proceedings, meeting abstracts, lectures and addresses, consensus development statements, conference abstracts, or poster presentation abstracts
  • Studies on patients who presented with comorbid conditions
  • Studies analyzing pooled data from interventions
  • Case studies, protocols, observational studies, or systematic reviews
  • Studies examining temporomandibular joint disorders
  • Studies conducted on animals
  • Studies that did not explicitly state a diagnosis of FM or MPS
Eligible studies were selected by two trained, independent reviewers from titles/abstracts and then full text. The reviewers met to reach consensus and involved a third reviewer if consensus could not be reached. Data was then extracted from 493 articles. Articles were initially grouped as FM or MPS. Extracted information pertaining to diagnostic criteria included: the use of the American College of Rheumatology (ACR) criteria or the trigger point manual as an authoritative publication; any additional published studies that were cited as being used as criteria; duration of symptoms; profession of the diagnosing healthcare professional; types of pain scales used; participant recruitment methods and any physical findings related to the diagnosis.

Study Strengths / Weaknesses:

Strengths:
  • An exhaustive, rigorous literature search was undertaken with the search strategy independently reviewed by a librarian.
Weaknesses:
  • Research on temporomandibular joint disorders or MTrPs as a cause of pain without explicitly relating them to MPS were excluded from this review. These articles may have yielded alternative sources and criteria for the diagnosis of FM or MPS that were therefore missed.
  • Articles published in any language other than English were excluded, again, possibly leading to the authors missing diagnostic criteria.
  • The criteria found in the published literature may not reflect the diagnostic criteria used in clinical practice (navigating this was one of the goals of this paper!).
  • No quality appraisal was performed due to the large number of articles included and the differences in the nature of the interventions. Therefore, it is possible that the included articles were of vastly different levels of quality.

Additional References:

  1. Gerwin RD. Classification, epidemiology, and natural history of myofascial pain syndrome. Current Pain and Headache Reports 2001; 5(5): 412-420.
  2. Jones GT, Atzeni F, Beasley M, et al. The prevalence of fibromyalgia in the general population: A comparison of the American College of Rheumatology 1990, 2010, and modified 2010 classification criteria. Arthritis & Rheumatology 2015; 67(2): 568-575. https://doi.org/10.1002/art.38905
  3. Shah JP, Thaker N, Heimur J, et al. Myofascial trigger points then and now: A historical and scientific perspective. PM & R 2015; 7(7): 746-761. https://doi.org/10.1016/j.pmrj.2015.01.024
  4. Stiell IG, Bennett C. Implementation of clinical decision rules in the emergency department. Academic Emergency Medicine 2007; 14(11): 955-959. https://doi.org/10.1197/j.aem.2007.06.039
  5. Tunks E, McCain GA, Hart LE, et al. The reliability of examination for tenderness in patients with myofascial pain, chronic fibromyalgia and controls. Journal of Rheumatology 1995; 22(5): 944-952.