The incidence of rheumatoid arthritis in Spain: results from a nationwide primary care registry.
OBJECTIVE
To estimate the incidence of early arthritis (EA) and of RA in adults (>16 yrs) in Spain.


METHODS
Primary care physicians were instructed in the detection of new cases using a checklist. All cases were evaluated at EA units (EAUs) within 15 days of detection. ACR criteria for the classification of RA were assessed every 6 months thereafter.


RESULTS
In an area covering 4,342,378 inhabitants over the age of 16 yrs, 2467 patients were referred to the EAU, of whom 1063 fulfilled EA criteria (43.1%). After 6 months, 362 patients fulfilled RA criteria. The estimated annual incidence of EA was 25/100,000 population (95% CI: 23, 26). The annual incidence of RA was 8.3 cases/100,000 (95% CI: 7.5, 9.2): 11.3/100,000 in women (95% CI: 10.0, 12.8), and 5.2/100,000 in men (95% CI: 4.3, 6.3). The incidence of RA increased with age in both sexes. At the 6 months' assessment, 187 (51.7%) of the patients with RA were RF positive. The presentation of RA was mainly polyarticular (n = 268; 74.0%). There were 701/1063 patients with EA who did not fulfil RA criteria by 6 months after the first rheumatologist visit. If all cases of undifferentiated arthritis (n = 118; 17%) became RA, the incidence would be in the range of 10 cases/100,000 population.


CONCLUSIONS
RA incidence in Spain is in the lower range of published data. The incidence of EA is about three times that of RA.
Rheumatology Department, Hospital del Mar, Institut Municipal Atencio Sanitaria, Barcelona.
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Carbonell
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Cobo
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Balsa
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Descalzo
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Carmona
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D001168:Arthritis / Q000175:diagnosis / Q000453:epidemiology; D001172:Arthritis, Rheumatoid / Q000453:epidemiology*; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011320:Primary Health Care / Q000706:statistics & numerical data; D012042:Registries; D017678:Sex Distribution; D013030:Spain / Q000453:epidemiology