Epidemiology of systemic sclerosis in a district of northern Italy

To estimate, using both the American College of Rheumatology-ACR 1980 classification criteria and revised LeRoy and Medsger 2001 criteria, the incidence and prevalence of systemic sclerosis (SSc) in an area in north-eastern Italy with a referral base population of about 346,000 inhabitants.

Retrospective examination of all patients 16 years and older of native Italian origin and resident in the Ferrara district who had either been admitted to hospital or referred to our outpatient clinic with a diagnosis of SSc between 1st January 1999 and 31st December 2007. SSc subjects were identified both by a search of hospital discharge code 710.1, as per the international classification of disease-9 codes, and using a computerised search for this pathology code in the national health care system. The subjects referred to our outpatient clinic were identified from a dedicated data base. Incidence and prevalence rates were calculated as the number of cases per 100,000 inhabitants (population data based on the October 2001 national census). The medical records of each potential case were accurately examined and reviewed by the same physician who determined whether those patients identified as having a diagnosis of SSc did indeed meet the ACR 1980 classification criteria for SSc and/or the LeRoy and Medsger 2001 criteria.

After reviewing all cases, of the 118 patients meeting the LeRoy-Medsger 2001 criteria, only 88 patients had a definitive diagnosis of SSc according to the ACR 1980 criteria. Considering the ACR criteria, the prevalence rate was 25.4 cases per 100,000 (95% CI: 22.2-28.6), and the annual incidence rate over the study period was 3.2 per 100,000 (95% CI: 2.0-4.4). Considering the LeRoy and Medsger criteria epidemiological data were respectively 34.1 cases per 100,000 (95% CI: 30.4-37.8) and 4.3 cases per 100,000 (95% CI: 3.0-5.6). According to the LeRoy and Medsger criteria, the SSc subsets were broken down as follows: 20 limited-SSc (19.2%), 76 limited cutaneous-SSc (62.1%), 22 diffuse cutaneous-SSc (18.7%). The female/male ratio was 9.7:1.

Incidence and prevalence of SSc observed in an area in north-eastern Italy were found to be higher than reported in the various geographical area (UK, US, Australia, etc.) but similar to another Italian study adopting, as here, the LeRoy-Medsger criteria. The different diagnostic criteria adopted may explain some of the differences found in comparison to the studies based only on the ACR criteria, however, regional discrepancies in disease occurrence cannot easily be dismissed only on the basis of methodological approaches to case definition or ascertainment; genetic, ethnic and environmental factors should also be considered. Currently the main challenge remains to determine the scientific basis for the observed differences, distinguishing between changes deriving from geographic/ethnic features and from the analytic methods.