Exploratory study into the relationship between the symptoms of chronic fatigue syndrome (CFS)/myalgic encephalomyelitis (ME) and fibromyalgia (FM)
By Dr. Pamela G. Mckay
Chronic fatigue syndrome (CFS)/myalgic encephalomyelitis (ME) and fibromyalgia (FM) are both identified as debilitating syndromes, with unclear/unknown aetiologies and no specific diagnostic tests or cure at the present time.1
CFS/ME and FM patients experience extensive polysymptomatology that affects all aspects of daily life, such as educational, economic and social, which has a great impact on their quality of life.2–7 Symptoms of CFS/ME include fatigue, headaches, muscle aches and pains, and/or joint pain.8 FM is characterised by chronic widespread musculoskeletal pain, persisting for ≥3 months, with an exhaustive list of additional symptoms.4 5 Ambiguity regarding the accuracy of diagnostic classification of CFS/ME or FM may have significant ramifications in terms of the management offered and the trajectory of patient care.6 9–11 Understanding the relationship between CFS/ME and FM is consequently vital in the delivery of effective, evidence-based and contextually appropriate clinical interventions.6 12–14
Thirty-eight criteria exist for diagnosing CFS/ME, with the American Centers for Disease Control and Prevention (CDC) Criteria being most frequently applied in research.15–17 This includes the National Institute for Health and Care Excellence (NICE) (2007) guidelines for CFS/ME, which are currently under review. The American College of Rheumatology (ACR)4 published the only diagnostic criteria for FM. This criterion was modified to focus on areas of pain and remove the controversial pain point assessment, which historically required patients to experience pain in 11 out of 18 highlighted points on the body when pressure was applied.5 Fibromyalgia Action submitted a proposal to NICE in 2007 recommending the development of guidelines, but this was subsequently rejected. The reasons cited were management/treatment of FM may be hindered by guidelines, as no diagnostic test exists and clinicians are not in agreement on the optimal management for FM.18 NICE stated that formal guidelines may create illness behaviour and hinder possible treatment options. This suggests that current guidelines may influence the restriction in management options offered to a patient with CFS/ME.
Research investigating whether CFS/ME and FM have the same underlying pathology is limited, and this may be an artefact of the traditional approach of diagnosing and managing these syndromes as two distinct entities.1 19 The research available concludes that CFS/ME and FM share many symptoms, but they do not agree if these syndromes are equivalent.12 20–24 Most of these studies were performed prior to the development and publishing of the accepted American CDC Criteria15 for CFS/ME, and when the ACR4 diagnostic criterion for FM was in its infancy, and although important in the context of this study, may now be considered obsolescent. Much of the literature available may discuss both together; however, little research actually investigates if the symptom experience is the same.1 24 Although diagnosis and management of CFS/ME and FM is improving, it is clear from the literature that there remains at this time no definitive biomedical cause identified, nor has there been a diagnostic test developed or a formal management strategy implemented. Diagnosis is a long drawn out process hindered by the subtle differences in the presenting symptoms such as location of pain and fatigue, where management options may be suitable for both CFS/ME and FM.8 11 14
Considering there has been little improvement in the clinical management for these patients, it was important to perform a study into the symptoms of CFS/ME and FM to create a contemporary understanding of the relationship. This is pertinent due to the restrictions that the NICE guidelines impose and the argument that has been presented as to why there are no FM guidelines. By re-examining the symptoms to improve the understanding of the relationship between them, and the challenges faced by patients, may provide evidence that CFS/ME and FM could be a single syndrome.
The purpose of this research was to assess the current relationship between the symptoms of CFS/ME and FM and to establish whether a relationship exists. In the absence of clear pathophysiology or diagnostic test, if the symptom experience is the same for both CFS/ME and FM, then this may have ramifications for the individual’s management. This process may identify new areas for review and be informative for medical practitioners who come into contact with CFS/ME and FM patients and influence care.
Data were screened prior to analysis to confirm that all participants met the requirements of the inclusion and exclusion criteria. The age range of participants was between 17 and 75 years. The CFS/ME group (n=101) had a mean (M) age of 45.52 years and the SD was 12.52 years, and for the FM group (n=107), M=47.20 years, SD=10.77 years. The CFS/ME sample comprised 85.2% (n=86) females and 14.8% (n=15) males. The FM group comprised 88.9% (n=95) females and 11.2% (n=12) males. Participants with CFS/ME 45.5% (n=46) were more readily diagnosed by a GP. In the case of FM, a greater portion were diagnosed by a rheumatologist (57.9% (n=62)).
All participants with CFS/ME confirmed that they had experienced their symptoms for the required ≥6 months15 and ≥3 months for a FM diagnosis.4 The CFS/ME group experienced their symptoms for a mean of 10.69 years (SD=8.91 years), ranging from 1 year to 37 years, exceeding the minimum requirements of 6 months. Participants with FM experienced symptoms for a mean of 12.62 years (SD=9.85 years), ranging from 1 year to 28 years, exceeding the 3-month history required for a diagnosis of FM.
The American CDC Symptom Inventory was used to assess the additional symptoms associated for both CFS/ME and FM. Both the CFS/ME 7.9% (n=8) and FM 1.8% (n=2) groups experienced a minimum of five additional symptoms listed by the American CDC criteria, confirming that both groups fulfilled the CFS/ME criteria, as they experienced ≥4 symptoms required.15 33 The maximum number of eight additional symptoms was experienced by the CFS/ME 49.0% (n=51) and FM 59.8% (n=61) groups (table 3). Table 3 highlights the number of participants who confirmed they had experienced a particular symptom in the past 6 months.
Participants responded in a similar manner to the questionnaire, confirming the same symptom experience. It is important to consider this in context with differing criteria and management guidelines, as this may influence diagnosis and the trajectory of patient’s management. With the biomedical cause currently unclear, it is the symptom experience and the impact on quality of life that is important. These findings are meaningful for patients, clinicians and policy development and support the requirement for future research.