Inaccuracy in the diagnosis of fibromyalgia syndrome: analysis of referrals

M.-A. Fitzcharles and P. Boulos1

Division of Rheumatology and McGill Pain Centre, Department of Medicine, Montreal General Hospital, McGill University Health Centre and
1 Division of Rheumatology, Department of Medicine, St. Joseph's Hospital, McMaster University, Canada


    Abstract
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Objective. To examine prospectively the accuracy of an initial diagnosis for fibromyalgia (FM).

Methods. All patients newly referred for rheumatology consultation in a 6-month period were evaluated prospectively for either a preceding, current or subsequent diagnosis of FM. Clinical characteristics, previous and subsequent management and health care utilization were assessed. The final diagnosis at 6 months was verified and accuracy regarding the diagnosis of FM was assessed.

Results. Seventy six (12%) of all new patients were either referred with a question of FM or finally diagnosed with FM. At the final evaluation the accuracy of the diagnosis regarding FM by either the referring physician or by the rheumatologist at the time of the initial visit was correct in 34% of patients. The FM group in comparison with those with some other rheumatological diagnosis had more tender points (12.5 vs 4) and were more fatigued. In contrast, prolonged early morning stiffness and limitation of lumbar spinal mobility in more than one plane was more common in the non-FM group.

Conclusion. There is a disturbing inaccuracy, mostly observed to be overdiagnosis, in the diagnosis of FM by referring physicians. This finding may help explain the current high reported rates of FM and caution physicians to consider other diagnostic possibilities when addressing diffuse musculoskeletal pain.

KEY WORDS: Fibromyalgia, Referral, Misdiagnosis.


    Introduction
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
During the last decade the fibromyalgia syndrome (FM) has become an accepted clinical entity characterized by diffuse musculoskeletal pain, a reduced pain threshold and identified by specific criteria [1, 2]. The prevalence of FM has been reported to be of the order of 2% in the general population, with women affected up to 10 times more commonly than men, and the frequency increasing linearly with age [3, 4]. Current understanding of the pathophysiology of FM suggests that dysfunction of central pain regulation and neuroendocrine mechanisms are probably important factors [57].

As many patients with musculoskeletal symptoms are mostly managed by primary care physicians, accuracy in the diagnosis of musculoskeletal complaints is important. Recent reports suggest that FM may be too readily diagnosed and that other medical conditions may be overlooked [8]. The pain of FM is characteristically widespread and may have been present for many years. In addition to the complaint of pain, patients may have other non-specific symptoms including sleep disturbance, fatigue and early morning stiffness [1, 9, 10]. FM is currently a fashionable diagnosis in North America, popularized by the lay press and conscientiously advocated by patient-focused groups. The cost of this illness in the United States and Canada as well as the burden of disease, to both the patient and society, has recently been reported to be considerable with more patients seeking disability benefits [1113]. Accuracy in the diagnosis of FM is thus of increasing importance.

The aim of the present study was to determine the accuracy of the diagnosis of FM in patients referred for rheumatology consultation. In addition, we sought to identify clinical characteristics that would help discriminate between patients finally diagnosed with FM and those with some other musculoskeletal diagnosis.


    Methods
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Patients
All consecutive newly referred patients to a university-affiliated community rheumatology practice were evaluated between September 1996 and February 1997. All new patients with a previous diagnosis of FM by the referring physician, a questionable diagnosis of FM by the referring physician or a final diagnosis of FM made by the rheumatologist were prospectively included into the study. The diagnosis of FM was based on the American College of Rheumatology (ACR) 1990 criteria [1]. Patients experiencing widespread pain, but with less than 11 of the 18 designated tender points on manual palpation, and with no other identifiable rheumatological condition, were classified as FM-like.

Data
All patients were evaluated at the baseline visit according to a predetermined protocol, which included information on patient demographics and symptoms, examination findings, previous and current investigations and management. Previous health care utilization included the category of referring physician, either primary care physician or specialist, and the number of previous physicians who had been consulted for the current musculoskeletal problem. All diagnoses were verified within a 6-month period, either by a follow-up visit, or a chart review and a telephone call to the patient. All discrepancies in diagnoses identified at the baseline visit or in follow-up by the rheumatologist were noted.

Clinical characteristics were reported as symptom description and physical examination findings. Symptoms relating to pain were recorded as follows: (i) duration of pain, defined as the time from onset of initial pain symptom; (ii) features of the onset of musculoskeletal pain were defined as: (a) pattern of onset of pain as one site (a single limb or part thereof, or a single region of the axial skeleton), multiple sites or widespread defined according to the ACR criteria as pain in the left side and right side of the body, above and below the waist and in addition, axial skeletal pain [1]; (b) location of pain at onset was categorized as spinal (cervical, thoracic or lumbar regions), root joint (shoulder or hip) or peripheral; (iii) current location of musculoskeletal pain was described as affecting the upper torso (neck, chest wall and thoracic spine), lower torso (lumbar spine and buttocks) or limbs (upper and/or lower). Additional information included a report of the following complaints: (i) disturbed sleep; (ii) early morning stiffness, defined as stiffness in the morning on rising, lasting for at least 1 h; (iii) fatigue, defined as tiredness and exhaustion sufficient to impair the patients' usual daily activities and (iv) the presence of inflammatory spinal pain [14].

The physical examination included: number of tender points according to ACR criteria [1]; spinal examination for presence of pain on movements of the cervical, thoracic and/or lumbar spine; reduction in range of motion in one or multiple planes of the cervical or the lumbar spine, or on rotation of the thoracic spine [15].

In addition, information was recorded by patient report regarding previous physicians consulted for the musculoskeletal problem, previous and current investigations, as well as treatments. All investigations performed in the preceding year for the purpose of identifying the musculoskeletal problem were noted. All current investigations requested by the consulting rheumatologist at the time of the study visit were recorded. Investigations were assigned a single value for each of the following categories: blood testing, plain radiographic studies and other investigations including scintigraphy, computed tomography (CT) and magnetic resonance imaging (MRI) scans. All treatments, both pharmacological and non-pharmacological, previously and currently prescribed were documented. Treatments were assigned a single value for each category as follows: analgesic, non-steroidal anti-inflammatory (NSAID), antidepressant, muscle relaxant, physiotherapy and other. The Montreal General Hospital University Ethics Committee approved the study and written consent was obtained from the subjects.

Statistical analysis
A univariate logistic regression analysis was performed on all independent variables. All variables with a P<0.2 were included in the multivariable logistic regression analysis. A stepwise procedure was used for final model selection. An exact method was utilized to determine the estimates and P values. All statistical analyses were performed using SAS/STAT (version 8.2; SAS Institute Inc., Cary, NC, USA) software.


    Results
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
A total of 626 new patients were evaluated during the study period, of which 76 (12%) were eligible for study. Referring and final diagnoses for these 76 patients are shown in Fig. 1Go. There were 61 females and the mean age was 48 yr (range 16–74 yr). The 13 patients referred with some other diagnosis included: arthralgia (nine), osteoarthritis (two), back pain (one) and palindromic rheumatism (one). The referring diagnosis regarding FM in this cohort of 76 patients was correct and upheld by the rheumatologist in 26 (34%) patients.



View larger version (18K):
[in this window]
[in a new window]
 
FIG 1. Flow chart of newly referred rheumatology patients.

 
The final rheumatological diagnosis at 6-month follow-up for all patients was FM (n=29), FM-like (n=10) and some other diagnosis categorized as non-FM (n=37). The 37 patients with some other diagnosis, all of whom had been referred with a diagnosis of FM, comprised 15 with inflammatory arthritis, which included inflammatory spondyloarthropathy in six, polymyalgia rheumatica in four, seronegative polyarthritis in four and rheumatoid arthritis in one; eight with soft-tissue rheumatism, which included hypermobility and tendonitis in four each; seven with degenerative arthritis; and seven with one of each of the following: antiphospholipid antibody syndrome, chronic fatigue syndrome, costochondritis, depression, myopathy, radiculopathy and thoracic outlet syndrome.

When the 10 patients with FM-like symptoms were compared with the 29 with definite FM, there were no significant differences observed for demographic or clinical data (results not shown), with the exception of more tender points present in the FM group (14 vs 8, P < 0.0001). For this reason the FM and FM-like groups were combined and analysed as a single group called the FM group. The patients with some other rheumatological diagnosis constituted the non-FM group.

Analysis of the FM and non-FM groups for demographic data and referral pattern was comparable. Ninety per cent of patients in each group were referred by primary care physicians, with four patients in each group being referred by some other specialist, a neurologist in two, and one each by the following specialists: cardiologist, gynaecologist, haematologist, orthopaedic surgeon, plastic surgeon and psychiatrist. Thirty-six per cent of patients in the FM group and 32% in the non-FM group had consulted some other specialist for their musculoskeletal complaint.

On analysis of all the independent variables collected, the following variables were significant in the stepwise logistic regression between the FM and non-FM groups, respectively: number of tender points 12.5 vs 4 (P< 0.0001), fatigue 79 vs 38% (P=0.0003), early morning stiffness 28 vs 49% (P=0.0014) and limitation of lumbar spine mobility in more than one plane 15 vs 30% (P=0.0115). Comparisons between the FM and non-FM groups for the following parameters are shown as follows: clinical symptoms in Table 1Go, physical examination in Table 2Go, and management and health care utilization in Table 3Go.


View this table:
[in this window]
[in a new window]
 
TABLE 1. Clinical characteristics of patients in FM and non-FM groups

 

View this table:
[in this window]
[in a new window]
 
TABLE 2. Physical examination for FM and non-FM groups

 

View this table:
[in this window]
[in a new window]
 
TABLE 3. Investigations and treatments for FM and non-FM groups

 
Both groups were comparable with regards to the number of previous investigations done, investigations initiated by the rheumatologist and previous treatments prescribed. At follow-up, nine of the 76 patients (12%) had a change in the initial diagnosis given by the rheumatologist as follows: five FM or FM-like patients were finally diagnosed with FM (two), tendonitis (two) and depression (one); three patients who were investigated for inflammatory spinal disease were finally diagnosed with mechanical spinal pain; and one patient with a polymyalgia rheumatica-like syndrome was found to have antiphospholipid antibody syndrome.


    Discussion
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Musculoskeletal pain is a common symptom in population studies, with FM increasingly recognized as a cause of diffuse musculoskeletal pain [3, 16]. However, there is concern that the diagnosis of FM is being made too freely, particularly in women. Our results demonstrate that in only 34% of patients presenting with musculoskeletal pain was the diagnosis pertaining to FM correct. In addition, 59% of patients referred with a diagnosis of FM had some other primary rheumatological process to account for symptoms. Inflammatory rheumatological conditions accounted for almost one-half of misdiagnoses. Diagnoses that were overlooked cover the spectrum of rheumatological conditions as well as some non-rheumatological ones.

Aside from the ACR criteria regarding tender point count for FM, our cohort of FM patients differed from the non-FM group in reporting more fatigue, but less early morning stiffness. There was an equally high rate of reporting of disturbed sleep in the two groups. Although disturbed sleep is a common complaint in FM, our results indicate that this symptom is as common in the non-FM group and thus may not be a useful discriminating symptom. In contrast, prolonged early morning stiffness, which is considered a marker of inflammatory musculoskeletal disease, although present in a quarter of the FM patients, was a significant discriminating clinical characteristic. Although almost half of the FM group reported that musculoskeletal pain was diffuse rather than localized at onset, supporting the concept of dysregulation of central pain processing mechanisms, this feature did not specifically help identify the FM patients. FM patients complained equally of upper and lower torso pain, which is in contrast to other reports indicating more neck pain in FM [12, 17]. Wolfe [17] has even suggested that axial pain in FM patients could be due to an increase in subclinical spinal disease, particularly in the older age group. Objective limitation in spinal mobility was not a prominent finding in the FM patients, but a complaint of pain was noted in half during lumbar spinal movement, and to a lesser extent on movement of the thoracic and cervical spines. The finding of mostly normal mobility of the spine on examination in FM suggests absence of significant disease of the axial skeleton and supports the concept of some other explanation for the report of pain.

Symptoms of FM are generally poorly responsive to various treatment interventions. It is therefore not surprising that there was a trend that the FM group had tried more therapeutic interventions prior to presenting to the rheumatologist. Our findings of 2.2 treatment categories tried by the FM group are in agreement with those of Campbell et al. [9], who reported that FM patients had used an average of three treatment interventions compared with 1.8 in patients with other musculoskeletal complaints. Previous investigations occurred with equal frequency in the two groups, but the FM group tended to be less likely to be further investigated by the rheumatologist. Although previous reports indicate that FM patients often undergo extensive and unnecessary investigations before the diagnosis is finally confirmed, this was not a finding in the present study [18].

The diagnosis of FM remains problematic. Previous studies have noted an increasing prevalence of this condition, especially within the community. Our study further raises the concern of the inaccuracy of the diagnosis of FM, predominantly by primary care physicians. Buskila et al. [19] have recently reported the lack of familiarity of family physicians with the diagnostic criteria for FM, which may be an explanation for the inaccuracy in both under- and overdiagnosis observed in the present study. A limitation of the present study is that our patients were assessed in a single rheumatology referral clinic and there could have been a selection bias towards more diagnostically challenging patients. It is also well recognized that rheumatological conditions may evolve, with the assignment of a final definitive diagnosis over time.

We have observed a disturbing inaccuracy in the diagnosis of FM in patients referred for rheumatology consultation. Common rheumatological conditions were overlooked and incorrectly labelled as FM, and in addition the diagnosis of FM was missed. We recommend caution in simply ascribing the diagnostic label of FM to patients with diffuse musculoskeletal symptoms and urge physicians to be more rigorous in the evaluation of rheumatological conditions. This high rate of inaccuracy in the diagnosis of FM should alert physicians to consider a wider spectrum of diagnostic possibilities in patients presenting with ill-defined aches and pains.


    Acknowledgments
 
Dr Boulos is supported by a combined Arthritis Society/Canadian Institutes for Health Research (CIHR) Research Fellowship Grant.


    Notes
 
Correspondence to: M.-A. Fitzcharles, Montreal General Hospital, McGill University Health Centre, 1650 Cedar ave, Montreal, Quebec, H3G 1A4. E-mail: mary-ann.fitzcharles{at}muhc.mcgill.ca Back


    References
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 

  1. Wolfe F, Smythe HA, Yunus MB et al. The American College of Rheumatology 1990 criteria for the classification of fibromyalgia. Arthritis Rheum 1990;33:160–72.[ISI][Medline]
  2. Gibson SJ, Littlejohn GO, Gorman MM, Helme RD, Granges G. Altered heat pain thresholds and cerebral event-related potentials following painful CO2 laser stimulation in subjects with fibromyalgia syndrome. Pain 1994;58:185–93.[CrossRef][ISI][Medline]
  3. Macfarlane GJ, Thomas E, Papageorgiou AC, Schollum J, Croft PR, Silman AJ. The natural history of chronic pain in the community: a better prognosis than in the clinic? J Rheumatol 1996;23:1617–20.[ISI][Medline]
  4. White KP, Speechley M, Harth M, Ostbye T. Fibromyalgia in rheumatology practice: A survey of Canadian rheumatologists. J Rheumatol 1995;22:722–6.[ISI][Medline]
  5. Griep EN, Boersma JW, Kloet ER. Altered reactivity of the hypothalamic–pituitary–adrenal axis in the primary fibromyalgia syndrome. J Rheumatol 1993;20:469–74.[ISI][Medline]
  6. Crofford LJ, Pillemer SR, Kalogeras KT et al. Hypothalamic–pituitary axis perturbations in patients with fibromyalgia. Arthritis Rheum 1994;37:1583–92.[ISI][Medline]
  7. Pillemer SR, Bradley LA, Crofford LJ, Moldofsky H, Chrousos GP. The neuroscience and endocrinology of fibromyalgia. Arthritis Rheum 1997;11:1928–39.
  8. Fitzcharles MA, Esdaile JM. The overdiagnosis of fibromyalgia syndrome. Am J Med 1997;103:44–50.[CrossRef][ISI][Medline]
  9. Campbell SM, Clark S, Tindall EA, Forehand ME, Bennett RM. Clinical characteristics of fibrositis. Arthritis Rheum 1983;26:817–24.[ISI][Medline]
  10. Wolfe F, Hawley DJ, Cathey MA, Caro X, Russel IJ. Fibrositis: Symptom frequency and criteria for diagnosis. An evaluation of 291 rheumatic disease patients and 58 normal individuals. J Rheumatol 1985;12:1159–63.[ISI][Medline]
  11. Wolfe F, Anderson J, Harkness D et al. A prospective, longitudinal, multicenter study of service utilization and costs in fibromyalgia. Arthritis Rheum 1997;40:1560–70.[Medline]
  12. Wolfe F, Anderson J, Harkness D et al. Health status and disease severity in fibromyalgia. Arthritis Rheum 1997;40:1571–9.[ISI][Medline]
  13. Capen K. The courts, expert witnesses and fibromylagia. Can Med Assoc J 1995;153:206–8.[Abstract]
  14. Calin A, Porta J, Fries J, Schurman DJ. Clinical history as a screening test for ankylosing spondylitis. J Am Med Assoc 1977;237:2613–4.[Abstract]
  15. Mau W, Zeidler H, Mau R, Majewski A, Freyschmidt J, Deicher H. Clinical features and prognosis of patients with possible ankylosing spondylitis. Results of a 10-year follow-up. J Rheumatol 1988;15:1109–14.[ISI][Medline]
  16. Wolfe F, Ross K, Anderson J, Russel IJ, Hebert L. The prevalence and characteristics of fibromyalgia in the general population. Arthritis Rheum 1995;38:19–28.[ISI][Medline]
  17. Wolfe F. The clinical syndrome of fibrositis. Am J Med 1986;81:7–13.
  18. Goldenberg DL. Fibromyalgia: why such controversy? Ann Rheum Dis 1995;54:3–5.[ISI][Medline]
  19. Buskila D, Neumann L, Sibirski D, Shvartzman P. Awareness of diagnostic and clinical features of fibromyalgia among family physicians. Fam Pract 1997;14:238–41.[Abstract/Free Full Text]
Submitted 14 January 2002; Accepted 15 July 2002





This Article
Abstract
Full Text (PDF)
Alert me when this article is cited
Alert me if a correction is posted
Services
Email this article to a friend
Similar articles in this journal
Similar articles in ISI Web of Science
Similar articles in PubMed
Alert me to new issues of the journal
Add to My Personal Archive
Download to citation manager
Search for citing articles in:
ISI Web of Science (9)
Disclaimer
Request Permissions
Google Scholar
Articles by Fitzcharles, M.-A.
Articles by Boulos, P.
PubMed
PubMed Citation
Articles by Fitzcharles, M.-A.
Articles by Boulos, P.
Related Collections
Other Rheumatology