Prevalence and incidence of rheumatoid arthritis in Italy.

Aim of the study was to estimate the prevalence and incidence of rheumatoid arthritis (RA) from an administrative cohort consisting of 2,268,514 males and 2,446,769 females, aged ≥ 18 years, from 32 Italian Health Districts. The diagnosis of RA was certified by a qualified specialist and confirmed by ≥3 prescriptions of "specific drugs" (corticosteroids, DMARDs or "biological" agents) during 2011. Patients on "specific drugs" qualified as "active RA"; those who never had more than 4 prescriptions in the past were classified as "unlikely RA," and those previously on chronic treatment but who discontinued therapy for >1 year were classified as "remission RA." The patients with a diagnosis of RA were 22,801 (0.48 %) with a prevalence of "active RA," "remission RA" and "confirmed RA" (Active + Remission RA) of 0.32, 0.09 and 0.41 % (95 % CI 0.38-0.44), respectively. The classification criteria tested in a fifth of the study population by direct analysis yielded >90 % accuracy and precision. The yearly incidence of "active RA" per 100,000 subjects was 48 (95 % CI 40-57) and 20 (95 % CI 10-30) for women and men, respectively. The peak for both prevalence and incidence was around the eighth decade of life. The female/male ratios for both prevalence and incidence were ca. 2.6 before the fifth decade of life, but approached unity in the ninth decade of life. The overall prevalence and incidence of RA in a large sample of the Italian population is only marginally lower than that reported from a similar administrative database of Sweden. With advancing age, the female/male ratio declines to about one.