The epidemiology of rheumatoid arthritis in Kinshasa, Democratic Republic of Congo--a population-based study.

OBJECTIVE To determine the prevalence of RA and its distribution among linguistic groups in the urban area of Kinshasa. METHODS Investigators questioned all individuals living in randomly chosen streets in five randomly chosen health areas in Kinshasa. Age, sex, linguistic group and rheumatic complaints were noted. RA diagnosis by 1987 ACR classification criteria was checked in all suspect cases. Disease activity (DAS-28), functionality (HAQ), X-ray damage, ACPA and RF positivity were assessed in patients confirmed with RA. RESULTS A total of 5000 individuals were questioned, with 2700 females and 2300 males [average age 25.7 (1.8) years]. Linguistic group definitions were obtained in 4587 subjects: 44.3% had Kongo roots, 16.9% Ngala, 16.7% Luba, 11% Swahili, 3.6% Tetela and 7.6% miscellaneous. Thirty persons (age ± 53 years) fulfilled the ACR criteria with a female/male sex ratio of 5. Mean age at disease onset was 47.7 years. Kongo people had the highest RA prevalence (1%). Mean DAS-28 was 6.5, mean HAQ was 1.3. One-third of patients were RF and ACPA positive and had classical X-ray findings. CONCLUSION The prevalence of RA in Kinshasa is 0.6 and 0.9% in people aged >18 years. Disease activity was high, but RF and ACPA positivity was not frequent. The Kongo seems to be the most affected linguistic group.