Fibromyalgia—worth a diagnosis?

Fibromyalgia (FM) is a protean chronic pain syndrome. In its pathophysiology the dysregulation of central pain processing (‘central sensitization’) is of pivotal importance, but peripheral input of nociceptic information, especially if chronic, also contributes to the development of full-blown FM (1). Although chronic widespread pain and allodynia (decreased threshold to painful stimuli, excessive tenderness) are the hallmarks of FM, other core symptoms include debilitating fatigue, non-refreshed sleep, cognitive problems, and excessive somatic symptoms reporting.

FM patients are frequently also co-morbid with psychiatric conditions such as depression and anxiety as well as stress-related disorders (2), but usually these are not the most emergent problems.

Chronic pain is prevalent. In epidemiological studies approximately 10%–15% of the population in Western countries of both genders suffer from chronic widespread musculoskeletal pain (CWP) (3). FM is significantly more common in females (3%–5%) than in males (0.2%–0.5%) (4). The gender differential for CWP and FM may be due to the American College of Rheumatology (ACR) 1990 classification criteria requiring at least 11/18 tender points (5), whose presence also correlates with psychological distress (1).

Physicians are trained to do diagnostics. Nevertheless, the majority of patients at primary care present symptoms which cannot be explained by any disease (6). On the other hand, authorities in rheumatology still debate whether the diagnosis of FM is justified (7), although most admit that ‘pain is real’ (8). Further, many physicians are reluctant to diagnose FM, since they are taught in medical schools to diagnose diseases, not obscure sets of symptoms. In fact, according to a survey amongst Norwegian physicians, the doctors rank FM as the least ‘prestigious’ illness (9).

Nevertheless, FM is worth a diagnosis. FM decreases function (10) and is costly both by increasing all kind of health service utilization (11) as well as work disability (10,12). The diagnosis does not affect adversely (13) but helps the patient to cope with the symptoms (14). More importantly, the diagnosis of a true case of FM leads to savings mostly due to decrease in health service utilization (15). Further, the patients with FM appear to be at increased risk to commit suicide (16,17).

In the present issue of Annals of Medicine, Wolfe and Häuser (18) put excellently into perspective the evolvement of the concept fibromyalgia from fibrositis, the conflict this chronic pain syndrome has generated and still generates within the medical community, as well as how various criteria to classify or diagnose a patient with FM have emerged.

The authors compare the recent ACR 2010 preliminary diagnostic criteria for fibromyalgia, compiled by a group of fibromyalgia specialists (19), with the previously composed ACR 1990 fibromyalgia classification criteria (5). The latter consist only of the recognition of CWP (at least for 3 months) and tender point palpation, while the 2010 criteria ignore manual physical examination. On the other hand, the 2010 criteria include the presence of CWP and emphasize the importance of other key features of FM: fatigue, unrefreshed sleep, cognitive problems, and extensive somatic symptom reporting. Expectedly, the criteria for the most part catch the same patients, although a total of 25% of the patients classified to have FM according to the ACR 1990 criteria did not cross-sectionally fulfil the ACR 2010 diagnostic criteria (19).

According to the authors the ACR 2010 diagnostic criteria facilitate the diagnosis of the FM syndrome. They stress that the criteria move the focus of diagnosis from palpable tender points to the key features of fibromyalgia (including fatigue, cognitive problems, and extensive somatic symptoms). Further, the new criteria are not, in contrast to the previous ACR 1990 classification criteria, dichotomous, but allow a compilation of a severity scale for each patient, which can be followed over time.

However, by elimination of the tender point count from the ‘diagnostic’ criteria they are left without a single ‘semi-objective’ measure of decreased pain threshold, a core finding of fibromyalgia patients. In fact, although claiming the opposite, the ACR 2010 criteria most probably will increase self-diagnosis. Self-diagnosis appears to be common even with the 1990 fibromyalgia classification criteria, as seen at the fibromyalgia web sites. More importantly, the patient can be diagnosed to have FM without a physical examination.

On the other hand, the severity scale is a major improvement of the 2010 diagnostic criteria. It allows the follow-up of the patients longitudinally.

Wolfe and Häuser state that it was necessary to develop new ‘diagnostic’ criteria for fibromyalgia, since general practitioners were unwilling or unable to examine tender point counts and the diagnosis was based on symptoms only. Also the ACR 2010 criteria require a detailed and thoughtful interview (to compile the severity scale) and a detailed assessment (for the widespread pain index) by the physician (19). Since general practitioners only have a limited time for each patient, the requirements most probably are unrealistic, and the diagnosis will be based on patients’ self-reports only. One can also argue that the ACR/EULAR preliminary classification criteria for rheumatoid arthritis (20) must be rejected, since general practitioners are unwilling and unable to examine tender and swollen joint counts as well. In my experience the recognition of swollen joints is far more difficult than to learn the palpation of tender points.

Another important issue raised by Wolfe and Häuser is that both diagnostic and classification criteria may falsely medicalize and legitimize fibromyalgia. The 1990 and the 2010 criteria are in this sense comparable.

The legislation and the authorities’ attitude to pain syndromes vary by country. In most countries pain syndromes are not accepted as legal grounds e.g. for early retirement. Pain syndromes are considered as symptoms and not as diseases, although most accept that chronic pain is real and it decreases both physical as well as intellectual performance of the patient. Measurable markers of pain states are lacking. Identification of such markers that are trusted by medical and legislative bodies is a major challenge, since pain is a complex, multidimensional experience that can be influenced by several physiological and psychological factors (21). Brain imaging has emerged as a promising objective method to document both acute and chronic pain states. It remains to be seen whether neuroimaging methods are able to separate various ‘endophenotypes’ of chronic pain states at the clinical level (21). Time will tell.

With regard to social benefits based on legislation, it is of no help whether pain syndromes have an international classification code of their own or not (fibromyalgia in ICD-10, M79.0). Fibromyalgia is definitely not a psychiatric disorder and should not be grouped under the category F in the ICD-10. Having a psychiatric diagnosis as depression, however, obviously makes a patient more legitimate and increases her/his odds of receiving social benefits, e.g. a positive decision of work disability and pension.

It is an advantage that the ACR 1990 classification criteria for fibromyalgia are not meant to be replaced by the ACR 2010 preliminary diagnostic criteria for fibromyalgia, but they should be considered as alternatives (19).

The ACR 2010 preliminary diagnostic criteria are suitable for e.g. postal prevalence surveys (22), while the ACR 1990 classification criteria are a more appropriate tool to diagnose an individual with this chronic pain syndrome at an office-based clinical check-up visit. The ACR 2010 preliminary diagnostic criteria for fibromyalgia state that the patient must not have another disorder that would explain the pain (19). On the other hand, concomitant chronic nociceptic pain and FM is common. To target therapies correctly the physician has to detect the presence of these two conditions. Without a thorough clinical examination this is not possible.

Finally, irrespective of which classification or diagnostic criteria are used, also the patients with somatoform syndromes and chronic pain states need a definite diagnosis. Only a firm diagnosis forms the grounds for a management strategy and enables proper therapy. Before the diagnosis of FM the physician should exclude more easily treatable painful (polymyalgia rheumatica, statin-induced muscle pain), fatiguing (hypothyreosis, anaemia), and miscellaneous symptom-generating (hyperparathyreosis, menopause) conditions. Uncertainty of diagnosis increases anxiety, repetitive testing raises unrealistic hopes of an undetected but curable disease, and renaming the symptoms with various diagnoses (depending on the specialty of the treating physician) only stimulates the pain spiral and increases the suffering of the patient.

Before having better tools to diagnose pain syndromes we have to classify them by the methods available. We physicians, however, should remember the priority of the profession. To help a suffering patient is more important than to classify syndromes correctly.

Declaration of interest: The author states no conflict of interest and has received no payment in preparation of this manuscript.