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% CI 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.