A study published in The Journal of Rheumatology recently reported a new classification system to assess patients with fibromyalgia. The study is entitled “The Use of Polysymptomatic Distress Categories in the Evaluation of Fibromyalgia (FM) and FM Severity” and was conducted by an international team at the National Data Bank for Rheumatic Diseases and the University of Kansas School of Medicine.
Fibromyalgia is a medical disorder characterized by a set of symptoms that includes widespread chronic musculoskeletal pain, incapacitating fatigue, stiffness and numbness in certain parts of the body, painful response to pressure, headaches, unrefreshing sleep (poor sleep quality), anxiety or depression and mood alterations. Fibromyalgia can affect people’s ability to conduct simple daily tasks, compromising their quality of life. It is estimated that 5 to 15 million Americans are affected by this disorder, especially women. The causes of fibromyalgia are unclear, but it is thought that genetic, neurophysiological and psychosocial mechanisms are involved.
The polysymptomatic distress (PSD) scale is a tool derived from variables established in the 2010 American College of Rheumatology (ACR) fibromyalgia diagnostic criteria, namely the Widespread Pain Index and the Symptom Severity Scale. The scale allows the assessment of the PSD effect in patients with a variety of pain-related clinical symptoms, and not just in patients who meet the fibromyalgia criteria. However, the PSD scale is not divided into categories that reflect disease severity in patients.
In this study, researchers developed clinical categories within the PSD scale. The team analyzed 2,732 patients with rheumatoid arthritis, an autoimmune disease that leads to chronic inflammation of the joints and other parts of the body and that can cause painful deformity and immobility of the fingers, wrists, ankles and feet. Patient data was collected from the National Databank for Rheumatic Diseases. Rheumatoid arthritis was selected because its symptoms can be remarkably similar with the ones in fibromyalgia, which can lead to misdiagnosis between the two conditions.
The team defined PSD severity categories ranging from none (score 0–3), mild (score 4–7), moderate (score 8–11), severe (score 12–19) and very severe (score 20–31). According to this system, fibromyalgia cannot be diagnosed unless the patient has a PSD score of at least 12. Pain, disease severity, functional status, physical and mental components, depression and anxiety were all variables analyzed. The Widespread Pain Index, in particular, was found to increase with PSD score, being 0% in patients in the none category, 18% in the mild category, 57.5% in the moderate category, 87% in the severe category, and up to 100% in the very severe category. PSD scores of 12 or higher were generally found to correlate with ACR criteria; however, not all patients with scores above 12 met the required criteria for a fibromyalgia diagnosis.
The research team concluded that the PSD categories defined are clinically relevant in terms of disease severity, and that this scale could be considered a useful diagnostic tool in fibromyalgia patients but also in patients without the disease.
“The advantages of the criteria / PSD scale as a measure of severity are several. First, the scale is simple to use and to score and is increasingly being used in patients with FM [fibromyalgia],” wrote the research team according to a news release. “Second, it provides a useful overall measure of FM severity. Finally, it can be used in all patients, not just those with FM — particularly because what is being measured with PSD is a universal quantity, not a score just used for FM.”