Background Monitoring of the incidence of inflammatory joint diseases may provide new insight into the etiology of these diseases.

Objectives All rheumatologists practising in the Northern Savo rheumatological outpatient departments collected data on their newly diagnosed patients with an inflammatory joint disease among patients over 16 years of age in 2010.

Methods All rheumatologists practising in the Northern Savo rheumatological outpatient departments collected data on their newly diagnosed patients with an inflammatory joint disease among patients over 16 years of age in 2010.

Results The incidence of all arthritis cases in the adult population was 142.0/100 000 (95% CI 126.2-159.2). The mean age at diagnosis for all patients with arthritis was 53.5±16.5 years. Sixty-nine patients, 38 men and 31 women, satis­fied the ACR 1987 classifica­ti­on criteria for RA. The incidence of RA by using the 1987 criteria was 33.4/100 000 (95% CI 26.0-42.3) and by the 2010 criteria 40.7/100 000 (95% CI 32.4-50.4) in the adult population. The incidence of RA for men and women according to the ACR1987 criteria was 37.6/100000 (95% CI 26.6-51.6) and 29.4/100000 (95% CI 20.0-41.7), respectively. The respective incidences among men and women in seropositive disease were 25.7 (95% CI 16.8-37.7) and 19.0 (95% CI 11.6-29.3) and in seronegative disease 11.9 (95% CI 6.1-20.7) and 10.4 (95% CI 5.2-18.7)/100 000. The incidence of undifferentiated arthritis was 47.5/100 000 (95% CI 38.6-57.9). This group included 13 (13.3%) cases with polyarthritis, 46 (46.9%) cases with oligoarthritis and 39 (39.8%) cases with monoarthritis. Of these 98 cases, 34 (34.7%) were male and 64 (65.3%) female. Twenty-eight (28.6%) were seropositive. In the spondyloarthritis group with 92 cases, the number of male and female patients was equal. The incidence of AS was 7.3 (95% CI 4.1-12.0), PsA 15.5 (10.6-21.9), ReA 7.3 (4.1-12.0), IBD associated arthritis 1.9 (0.5-5.0) and unspecified spondyloarthritis 9.7(5.9-15.0)/100 000. The incidence of gout was 11.6 (7.4-17.3) and calcium pyrophosphate arthritis 2.9 (1.1-6.3)/100 000 and the incidence of sarcoid arthritis and arthropathy in thyroid disease were 1.5 (0.3-4.3) and 0.5(0.0-2.7)/100 000. The mean age at diag­nosis was 62.6± 11.8 years for all patients with RA; 60.1± 10.5 years for men 64.2 ± 13.5 years for women, (p = 0.164). Fourty-six patients (66.7 %) had seropositive RA and 23 patients seronegative RA and there was no significant age difference between the groups, p=0.742. In patients with RF+ RA the peak incidence occurred in the age group of 55-64 years among men and 65-74 years among women.

Conclusions In the present study the incidence of RF-positive RA was higher among men than among women. The peak incidence in men also occurred in the younger age-group than in women. The incidences of other inflammatory joint diseases were in accordance with earlier literature reports.

References Savolainen E, Kaipiainen-Seppänen O, Kröger L, Luosujärvi R. Total incidence and distribution of inflammatory joint diseases in a defined population: results from the Kuopio 2000 arthritis survey. J Rheumatol. 2003;30:2460-8.

Disclosure of Interest None Declared