Results

The cumulative response rate to the screening questionnaire was 73.9% (3294 of 4456). The response was similar for women (73.2%) and men (74.8%). The mean (SD) age of the 3294 responders was 48.3 (19.3) years and that of non-responders was 50.7 (21) years. The response varied between practices and was comprised between 68.5% and 77.4%.

Swelling in at least two symmetrical joints was reported by 230 (7%) subjects whose clinical evaluation was deemed necessary. Among them, 11 patients fulfilling the modified 1987 ARA criteria for RA were identified (table 1). Only nine patients fulfilled the traditional 1987 ARA criteria, 10 the 1958 ARA criteria, and seven the New York criteria (with the three out of four format). Seven were identified by visit and four by clinical records of no shows. Two more subjects gave a history of possible rheumatoid polyarthritis in the past but had no convincing clinical records, compatible radiology, or evidence of deformity or clinical synovitis. Of the 11 patients, nine were women and two men. Ten of 11 patients were over 55 years. IgM rheumatoid factor was present in six patients and erosions in seven. EAMs were seen in three of the eight patients who had complete clinical data. Two patients showed Sjögren’s syndrome and one had nodules and vasculitis. Two patients were in clinical remission. Disability was absent in four of seven patients (table 1). The prevalence of RA was 0.33% (95% CI 0.13, 0.53) in the general population, 0.13% (95% CI 0, 0.31) in men, and 0.51% (95% CI 0.18, 0.84) in women. To obtain minimum estimates, RA prevalence has been also calculated considering that non-responders had the same prevalence of second time responders and that none of the non-attenders to the visit had RA. The resulting values were 0.26% and 0.21%, respectively. Both values are well within the confidence limits of our original prevalence. Three of 11 cases of RA had not been previously diagnosed by a physician.

The other sources of information were much less sensitive. Of the 11 RA patients identified in this study only five had been visited in the rheumatology outpatient clinic of the local hospital; they were also listed in the exemption group.

The 1162 non-responders included 15 subjects who returned incompletely answered questionnaires, 70 subjects who died, and 166 subjects who moved during the study period. The analysis of their clinical records revealed five additional patients with RA. This raised the total number of RA patients to 16 with a cumulative prevalence that remained nearly unchanged at 0.36%.

Discussion

This is one of the few studies evaluating the lifetime cumulative prevalence of RA in southern Europe and confirms the impression of a low frequency of the disease in this area. It is difficult to compare our figures with those of previous studies for two main reasons. Firstly, the diagnostic definition of RA has changed over time and different methods have been used in the literature to ascertain RA cases. In addition, most studies report point prevalence, not lifetime prevalence. Secondly, comparing studies performed in different years is probably not correct because the incidence of RA may vary with time. The modified version of the 1987 ARA criteria was more sensitive than the traditional one, the 1958 ARA criteria and the New York criteria (3 of 4). Only the latter, when considered positive by satisfying two or more criteria, identified all the patients. The questionnaire developed by the ARC Epidemiology Unit, which has been recently used in a number of studies, permits direct comparison with data from different geographical areas. The prevalence of RA in Italy is higher than that observed in Pakistan (0.14%),10 similar to that observed in black Caribbeans living in Manchester (0.29%),7 and in Hong Kong orientals (0.35%)11 but lower than that observed in a white population from Manchester (0.8%).7

The response rate to the questionnaire and to clinical assessment was not high but nevertheless in keeping with the results obtained in most postal surveys from southern Europe. Because of non-responders, ascertainment of RA cases was based in part on the review of clinical records. This fact may have hampered the evaluation of transient or limited disease thus leading to undereporting of RA. However, our data are consistent with the results of three well performed studies published in the fifties in the Italian literature.12-14In 1956, Neri Serneri and Bartoli reported a 0.38% prevalence in Tuscany (0.54% in women and 0.21% in men).12 In 1963, Einaudi reported a similar value (0.35%) in Piedmont (0.46% for women and 0.24% for men).13 Finally, in 1967, Marcolongoet al found a prevalence of 0.43% in Tuscany (0.63% in women and 0.25% in men).14

Most of the studies on RA prevalence in Anglo-Saxon populations show evidence of a secular decline.5 6 As this trend was not observed in Italy, we suggest that the putative environmental protective factor was not present in our country. Oral contraceptives, a possible candidate for the decline of RA, are used by a smaller percentage of women in Italy in comparison with those northern Europe and could explain the lack of decrease in RA prevalence. Accordingly, also the finding that most of the patients were older than 55 years may be related to a changing pattern of age distribution as a result of a birth cohort trend with recent generations less likely to develop RA.

As expected from a population survey, several patients had mild disease or were in remission with low disability scores. However, most patients showed positive RF and erosions. EAMs were present in three of eight (37.5%) patients, an observation that is in keeping with those of Salvarani et al who showed a 32% frequency of EAMs in Italian outpatients with RA.3 In this study and in Salvarani’s, Sjögren’s syndrome accounted for most of the EAMs.

In conclusion, our results confirm that the prevalence of RA is low in Italy and similar to that reported over the last 40 years. This finding should encourage further studies to identify the genetic and environmental protective factors that may be at work in our area.