Although fibromyalgia criteria have been in effect for decades, little is known about how the fibromyalgia diagnosis is applied and understood by clinicians and patients. We used the National Health Interview Survey (NHIS) to determine the prevalence of self-reported clinician diagnosed fibromyalgia and then compared demographics, symptoms, disability and medical utilization measures of persons with a clinical diagnosis of fibromyalgia that did not meet diagnostic criteria (false-positive or prior [F/P] fibromyalgia) to persons with and without criteria-positive fibromyalgia.
The National Health Interview Survey (NHIS) collected information about both clinical diagnosis and symptoms of fibromyalgia that was appropriately weighted to represent 225,726,257 US adults. Surrogate NHIS diagnostic criteria for fibromyalgia were developed based on the level of polysymptomatic distress (PSD) as characterized in the 2011 modified American College of Rheumatology criteria (ACR) for fibromyalgia. Persons with F/P fibromyalgia were compared with persons who do not have fibromyalgia and those meeting surrogate NHIS fibromyalgia criteria.
Of the 1.78% of persons reporting a clinical diagnosis, 73.5% did not meet NHIS fibromyalgia criteria. The prevalence of F/P fibromyalgia is 1.3%. F/P fibromyalgia is associated with a mild degree of polysymptomatic distress (NHIS PSD score 6.2) and characterized by frequent but not widespread pain and insomnia. Measures of work disability and medical utilization in F/P fibromyalgia were equal to that seen with NHIS criteria positive fibromyalgia and were 6-7x greater in F/P fibromyalgia than in non-fibromyalgia persons. F/P fibromyalgia was best predicted by being female (Odds Ratio [OR] 8.81), married (OR 3.27), and white (OR 1.96). In contrast, being a white, married woman was only modestly predictive of NHIS (criteria positive) fibromyalgia (OR 2.1).
The majority of clinically diagnosed fibromyalgia cases in the US do not reach levels of severity necessary and sufficient for diagnosis. The clinical diagnosis of fibromyalgia is disproportionally dependent on demographic and social factors rather than the symptoms themselves. Diagnostic criteria for fibromyalgia appear to be used as a vague guide by clinicians and patients, and allow for substantial diagnostic expansion of fibromyalgia.