SIFIS

Fibromyalgia is a complex and debilitating disease characterized by chronic widespread muscle pain and fatigue, associated with rigidity and a wide range of functional disorders (headache, irritable bowel, interstitial cystitis, sleep disorders, cognitive disorders, restless legs syndrome, etc.) that can seriously compromise the quality of life of the patient. The prevalence of fibromyalgia is estimated in Italy in the order of 2.2% of the general adult population (1). It mainly affects women, with a female-male ratio of 8: 2, and the prevalence of the disease increases with advancing age. Over the years, numerous diagnostic and classification criteria have been developed that include, in addition to widespread chronic pain, many somatic and cognitive symptoms (2,3). These criteria are still difficult to apply in ambulatory clinical practice and are rarely used as screening tools.
The SIFIS - SImple FIbromyalgia Screening questionnaire, is proposed as a valid screening tool, easy to use in outpatient practice and certainly useful in epidemiological studies. The different stages of the development of the SIFIS involved: (1) the identification of a specific population of patients, (2) the development and selection of a large number of items, (3) the simplification of the number of items, and ( 4) the final validation tool of the instrument, conducted on 230 patients with fibromyalgia. Sensitivity, specificity, positive predictive values, likelihood ratios (LR + and LR-) and post-test probabilities of the 6 items identified were determined in order to study the best possible combination. The LR + value of the 6 items was between 3.37 and 5.00. The verification of the post-test probability was investigated using the Bayes formula (or Bayes theorem or the probability of theorem) and the mathematical algorithm was implemented in the application.