Incidence and Prevalence of Polymyalgia Rheumatica (PMR): The Importance of the Epidemiological Context. The Italian Case

Objectives: to evaluate incidence and prevalence rates of polymyalgia rheumatica (PMR) in Italy, depending on the epidemiological methodology used from time to time. Materials and Methods: A comprehensive literature search in MEDLINE and EMBASE was carried out. The following search terms were used: polymyalgia rheumatica, incidence, prevalence, epidemiology, general practitioner, family medicine, Italy. A search was also carried out in Google scholar using the search phrase: epidemiology of polymyalgia rheumatica in Italy. The period considered was between 1970 and March 2019. All articles containing data on incidence and prevalence of PMR in Italy were read in full. Reviews and non-original manuscripts were excluded as well as all the studies containing incidence and prevalence rates of giant cell arteritis (GCA), unless clearly distinct from data related to patients with PMR alone (isolated and pure PMR). Results: Five articles corresponded to inclusion and exclusion criteria. Two articles were excluded as they were review articles, and three articles were excluded because there were not clear data on incidence and prevalence rates of isolated PMR. Three articles reported data on the annual incidence of PMR (two of them published by the same group of investigators); two articles reported prevalence data. In one article, both incidence and prevalence were calculated. The annual rate of incidence of PMR was between 0.12 and 2.3 cases/1000 inhabitants aged over 50 years. In the two studies publishing prevalence data, they varied from 0.37% to 0.62%. The differences in incidence and prevalence rates were related to several factors such as the different set of diagnostic criteria used for identifying patients or the diagnostic difficulty for patients with atypical presentations, specifically those without raised erythrocyte sedimentation rate (ESR). In the study with higher annual rate of incidence and higher prevalence of PMR, the collaboration between general practitioner (GP) and the out-of-hospital public rheumatologist resulted in significantly different data than in the other studies. All the five articles presented data from monocentric cohorts. Conclusion: Very few Italian studies addressed the epidemiology of PMR. The contribution of a specific professional figure represented by the out-of-hospital public rheumatologist, present in the Italian National Health System and absent in other countries, can make the Italian experience unique in its kind.