Assessment of the Functional Capacity of Patients with Fibromyalgia: Clinical Validity

Assessment of the Functional Capacity of Patients with Fibromyalgia: Clinical Validity and in the Determination of Work Incapacity

Fibromyalgia is one of the main causes of chronic pain without a specific etiology, affecting 8% of the Spanish population, especially women. Its most characteristic symptoms include generalized pain, fatigue, difficulty falling asleep, joint stiffness, anxiety, and depression. Due to the lack of objective data confirming the condition and the subjectivity of the symptoms, the current diagnosis is purely clinical. Moreover, despite the significant impact on the quality of life of those who suffer from it, there is a lack of scientific evidence to assess the degree to which it affects their functional and work capacity. This concept is gaining relevance in the growing context of patients seeking work disability.

Thus, due to the lack of international consensus and standardized protocols, this study hypothesizes that the functional capacity of Spanish women with fibromyalgia, aged 30 to 64, evaluated with various validated tests such as the six-minute walking test (6MWT), handgrip strength dynamometry, and the 8-foot up & go, correlates directly with their quality of life, physical activity measured by accelerometry, and social and psychological impact, provided there is no economic benefit. Therefore, the primary aim of this research is to validate a standardized protocol for evaluating the functional and work capacity of Spanish women with fibromyalgia and to assess its correlation with quality of life, physical activity, and psychosocial impact.

The study will include a total sample of 160 women, divided into four groups of 40 participants: women with fibromyalgia who are actively working, women with fibromyalgia on sick leave, women with fibromyalgia with permanent work disability (officially recognized by the National Institute of Social Security, INSS), and a control group of healthy women.

The patients will be required to attend in person to complete the full protocol, with a one-week interval between sessions. Subsequently, two follow-ups will be conducted at 6 and 12 months, where the work situation will be reassessed, and questionnaires will be administered. The protocol includes the following variables for study: age, weight, height, marital status, country of origin, socioeconomic level, educational level, occupation, work situation, generalized pain index questionnaire, symptom severity questionnaire, fibromyalgia impact questionnaire, allodynia test, six-minute walking test, 8-foot up and go, handgrip strength dynamometry, tender points, false points, SF-36 questionnaire, Hospital Anxiety and Depression Scale, multidimensional perceived social support scale, and accelerometry.

The aim of this study is to analyze in greater depth the validity of the tests currently used in clinics to objectively assess the functional capacity of patients with fibromyalgia. In this way, this study will become the first to present and evaluate the validity and reliability of a protocol for assessing functional capacity. If the proposed hypothesis is proven, these tests and evaluation methods will be highly useful for systematic incorporation into the routine of functional capacity assessment services, as well as in daily clinical practice.

Inclusion Criteria:

• Women aged between 30 and 64 years old with a diagnosis of fibromyalgia made by a rheumatologist or family doctor following the ACR diagnostic criteria.
• For the control group, women matched by age with no diagnosis of fibromyalgia and with a sedentary lifestyle will be included.
• All participants must agree to be part of the study.

Exclusion Criteria (for both case group and control group):

• Illiteracy and/or lack of understanding of Spanish.
• Severe psychiatric and/or psychological disorders, associated musculoskeletal diseases that could increase pain, such as uncontrolled endocrine disorders, autoimmune diseases, and/or other associated rheumatological or neurological conditions.
• Additionally, patients who refuse to participate in the study or any condition that, in the investigator's judgment, would prevent proper adherence to the protocol will be excluded.