The prevalence and incidence of biopsy-proven lupus nephritis in the UK - Evidence of an ethnic gradient

Objective. Renal involvement is a major complication of systemic lupus erythematosus (SLE) and is a strong determinant of morbidity and mortality. There have been no previous studies of the epidemiology of lupus nephritis. Our aim was to establish the prevalence and incidence of biopsy-proven lupus nephritis in the northwest of England in 2001 and to examine the influence of age, sex, and ethnicity. Methods. Adults (age 18 years and older) with biopsy-proven lupus nephritis were identified from 5 sources: renal biopsy databases, dialysis/transplant databases, nephrologists' patients, clinic lists, and lupus patient groups. The denominator data for the northwest of England were ascertained from the 2001 census. Results. We identified 208 cases of biopsy-proven lupus nephritis (176 women, 32 men): the overall prevalence was 4.4 per 100,000 population (95% confidence interval [95% CI] 3.8-5.0), 7.1 per 100,000 (95% Cl 6.1-8.2) in women, and 1.4 per 100,000 (95% CI 1.0-2.0) in men. The prevalence was significantly higher among women in the ethnic subgroups: 110.3 per 100,000 population (95% CI 55.0-197.3) in Chinese patients.. 99.2 per 100,000 (95% CI 55.5-163.6) in Afro-Caribbean, 21.4 per 100,000 (95% CI 12.0-35.2) in Indo-Asian (Asians from the Indian subcontinent), and 5.6 per 100,000 (95% CI 4.7-6.7) in white patients. The overall annual incidence rate was 0.40 per 100,000 population per year (95% CI 0.24-0.63), with a rate of 0.68 (95% CI 0.40-1.10) in women and 0.09 (95% CI 0.01-0.32) in men. Capture-recapture methods. did not suggest any additional cases. Conclusion. This first estimate of the prevalence and incidence of biopsy-proven lupus nephritis demonstrates dramatic differences in prevalence according to ethnicity, with an increasing gradient from the white to the Indo-Asian, Afro-Caribbean, and Chinese populations.