Short summary

All newly referred patients to an outpatient rheumatic clinic were evaluated for FM using the 2011 survey criteria for FM during a 6-month period. Demographic data were obtained and 7 years later patients' medical journals were evaluated and comparisons between groups were made.

Results: 36% fulfilled FM criteria. More FM patients had undergone invasive procedures, had higher number of outpatient courses, and consulted more different specialists.

Rationale

Fibromyalgia (FM) has been subject to controversy since the development of classification- and diagnostic criteria. Several clinicians do not recognize FM as either a disease or disorder, and studies have proven FM underdiagnosed. For instance, one study demonstrated that FM in as many as 75% of cases is left undiagnosed, and epidemiological studies in Japan and Germany have documented that only 2.5 % and 14% of patients satisfying survey criteria for FM have been given this diagnosis respectively.

To date, the diagnosis of FM is given if patient-reported symptoms meet the predefined criteria for FM, and no other explanation can be identified.

The most common symptom leading to referral to rheumatic outpatient clinics is pain and the suspicion of either osteoarthritis or systemic inflammatory rheumatic disease. However, FM is an obvious differential diagnosis when evaluating the origin of pain in patients. Refraining from considering FM as a possible explanation of their symptoms can leave the patients search for an answer unrequited. This often leads to extensive examination in the health care system, and numerous studies have documented that patients fulfilling criteria for FM have substantial healthcare costs and increased work disability compared to the general population. The overall conclusion is that FM patients often have increased consumption of medicine, more visits to their general practitioners, extensive comorbidity, more use of complementary therapists, and an increased number of specialist consultations. However, no study has directly documented the burden of FM in the different medical specialties.

The prevalence of FM has been widely investigated throughout the different continents ranging from 0.2 to 6% in the general population depending on the criteria used for identifying FM patients. Furthermore, prevalence studies of FM have been conducted in many subpopulations, such as in different ethnic groups, urban and rural regions, train-crash survivors, and women. However, to the authors' knowledge, no prevalence study of FM exists concerning newly referred patients to rheumatic outpatient clinics. Thus, the aim of this study is to descriptively examine the prevalence of FM (defined as the fulfillment of 2011 survey criteria for FM by questionnaire) and its impact on the hospital burden among newly referred patients to a rheumatic hospital clinic.

Our primary objective is to compare the use of the healthcare facilities (i.e., burden) in the secondary hospital sector between FM patients, relative to non-FM patients, during a seven-year period.

We consider the number of courses as the most important measurement when evaluating the use of the health care system(s) in the secondary sector at hospitals. Secondary objectives include comparing the effect of FM, relative to non-FM, on number of diagnoses, number of admissions to hospital, number of doctors' notes in patients' medical journal, other rheumatic diseases, and medical use. Finally, the effect of FM, relative to non-FM, is compared regarding invasive procedures performed and consultations in different medical specialties from baseline and up to seven years follow-up.

Description of the cohort

Study design

This study was designed as a single-centre observational prospective cohort study with consecutive enrolment.

In 2013 during a 6-month period (March to October), newly referred patients (at any cause) in an outpatient rheumatic clinic at the regional hospital of Southwest Denmark, Esbjerg, were screened for FM by self-administered questionnaires based on the 2011 survey criteria for FM.

In 2020 questionnaire data were transferred to a database. Patients' medical journals were identified by the social security number noted by the study subjects in the original questionnaire. Patients' electronic journal files were then evaluated, and relevant data (all data regarding the patient's medical history obtained at any hospital in the region during the period) was transferred to the database. The total number of current medications, including pain medications, was retrieved through the online medication facility.

Based on the answers to the questionnaires, patients were divided into two groups depending on the fulfilment of survey criteria for FM, and comparisons were made regarding the use of the secondary healthcare facilities during the observation period. All data were prospectively collected in patients' journals; however, data was (as described above) transferred to the final database simultaneously at seven years follow-up.

Data and biological material

Study participants are described with respect to age at inclusion, sex, smoking status, working status, marital status, widespread pain index (WPI), Symptom severity score (SSS), including the responsible subunits of the final SSS based on their answers to the questionnaire. At follow-up, number of diagnoses at inclusion, presence of rheumatic inflammatory disease, number of medications-, and number of pain medications at inclusion is obtained separately for the two groups (FM versus Non-FM respectively) by journal assessment as previously described. During the following seven years, all variables of interest were prospectively collected from the patients' journals by their treating physicians in the secondary sector of the public healthcare system. The outcome variables are as follows: number of different courses at hospital, number of chronic diagnoses, description of surgical or diagnostic procedures performed at any hospitals in the region, and a list of the specific medical specialties consulted. Furthermore, the number of doctors' notes in the journal, admissions to any hospital in the region, number of medications and pain medications prescribed, along with the number of different medical expertise's consulted is noted at 7 years follow up.