Racial and ethnic disparities in systemic lupus erythematosus, and one of its worst complications, kidney failure, continue to grow in the U.S. The number of new cases of kidney failure due to lupus occurring among African Americans has now surpassed that in Caucasians, with a high proportion occurring among African American women, according to research presented this week at the American College of Rheumatology Annual Scientific Meeting in San Francisco, Calif.

Lupus nephritis is an inflammation of the kidney cased by systemic lupus erythematosus (also called SLE or lupus) – a chronic inflammatory disease that can affect the skin, joints, kidneys, lungs, nervous system, and/or other organs of the body.

Researchers used information from two data sources, the National Arthritis Data Workgroup national and regional surveys of national prevalence rates of various rheumatic diseases, and the U.S. Renal Datasystem, to study kidney failure among patients with lupus. Based on 2005 U.S. Census data, lupus is most common among African Americans women, striking 400 out of 100,000 African American women; 100 out of 100,000 white women; 50 out of 100,000 African American men; and 10 out of 100,000 white men 15 – 64 years of age.
The U.S. Renal Datasystem includes data on approximately 94 percent of all U.S. patients with kidney failure, also known as end-stage renal disease.

Researchers examined changes in the number of new cases per year, or incidence, of end-stage renal disease due to lupus nephritis in the entire U.S. population between 1995 and 2004. A total of 10,035 cases of end-stage renal disease due to lupus nephritis occurred during this time period. The number of new cases per year rose 30 percent in the entire population. Researchers discovered the highest number of cases in the 20 – 39 year old age group. The majority of cases—82 percent—occurred among women, and the number of new cases per year among women increased 32 percent.

Additionally, this is the first study to show that the incidence rate of kidney failure due to lupus nephritis is now higher among African Americans than Caucasians. The 37 percent increase in incidence among this group was higher than that among any other racial and ethnic groups. Overall, the proportion of new cases per year of lupus kidney failure in African Americans increased from 45 percent to 49 percent – with a corresponding drop in the proportion occurring in Caucasians (dropping from 47 percent to 42 percent during the study period).

Researchers noted that the increased incidence of kidney failure due to lupus among African Americans occurred despite clinical trials demonstrating the effectiveness of immunosuppressant therapies in the prevention of end-stage renal disease in lupus nephritis – suggesting that there may be decreased or differential access to care and/or decreased effectiveness of these therapies for lupus nephritis in African Americans.

“In examining the incidence of end-stage renal disease caused by lupus in the U.S. according to age, sex, and racial/ethnic groups, we have found that the incidence is much higher in all minority racial and ethnic groups than in whites, and this ‘gap’ continues to widen,” says lead investigator in the study, Karen H. Costenbader, MD, MPH; assistant professor of medicine, Harvard Medical School, Division of Rheumatology, Immunology and Allergy, Brigham and Women’s Hospital, Boston, Massachusetts. “Incidence rates over the years examined were almost ten times higher among African American women than among Caucasian women, ages 20—39. The absolute incidence of end-stage renal disease due to lupus among African Americans surpassed that among Caucasians, while African Americans constituted 13 percent of the U.S. population during these years. Our findings suggest that possibly minority racial and ethnic groups in the U.S. are not receiving adequate health care for lupus and lupus nephritis, and/or they are not responding to treatment in the same way as Caucasians.”

The ACR is an organization of and for physicians, health professionals, and scientists that advances rheumatology through programs of education, research, advocacy and practice support that foster excellence in the care of people with or at risk for arthritis and rheumatic and musculoskeletal diseases. For more information on the ACR’s annual meeting, see http://www.rheumatology.org/annual.

Editor’s Notes: Dr. Costenbader, will present this research during the ACR Annual Scientific Meeting at the Moscone Center from noon – 12:15PM on Tuesday, October 28, in Hall C. Dr. Costenbader will be available for media questions and briefing at 8:30 AM on Tuesday, October 28 in the on-site press conference room, 114.

Presentation Number: 1927

Incidence of End-Stage Renal Disease Due to Lupus Nephritis in the U.S.,1995-2004

Karen H. Costenbader, Daniel H. Solomon, Wolfgang Winkelmayer, M. Alan Brookhart. Brigham and Women’s Hospital, Boston, MA

Purpose: Changes in the incidence of end-stage renal disease (ESRD) due to lupus nephritis within the U.S. population have not been studied since the early 1990s. We aimed to examine nationwide incidence of ESRD due to lupus nephritis from 1995-2004, and to investigate incidence rates in different sociodemographic groups.

Methods: We examined incidence rates of ESRD due to lupus nephritis using the U.S. Renal Datasystem, which includes data on approximately 94% of all U.S. patients with ESRD. Lupus as the cause of ESRD was identified from the medical evidence enrollment form. Age group-, sex-, and race- and ethnicity- stratified data from the 2000 U.S. Census and annual population estimates from 1995-2004 were used to calculate standardized incidence rates. We examined changes in the incidence of ESRD due to lupus nephritis in the entire U.S. population and stratified according to age, sex, race and ethnicity (US Census definitions).

Results: 10,035 incident cases of ESRD due to lupus nephritis occurred in the U.S. between 1995 and 2004. In the entire population, the incidence rate rose from 3.0 to 3.9 cases per million person-years. When stratified by age, the standardized incidence rates were highest in the 20-39 year old age group (6.5/million person-years in 2004). The majority of cases occurred among women (82%) and the standardized incidence rate in women increased 32%, from 4.7 to 6.2/million person years during this time. The 37% increase in incidence among Blacks (10.5 to 14.4/million person years) was higher than that among other racial and ethnic groups. Overall the proportion of Blacks among incident cases increased from 45% to 49%, exceeding that of Whites, which fell from 47% to 42%. (Fig. 1) In 2004, the standard incidence rates for ESRD due to lupus nephritis were 14.4/million person-years among Blacks, 4.6/million person-years among Hispanics, 3.8/million person-years among Asians and Pacific Islanders, and 2.0/million person-years for Whites.

Conclusions: The incidence of ESRD due to lupus nephritis rose in the U.S. population from 1995 and 2004. This increase was disproportionately observed among women and Blacks. For the first time, the absolute incidence rate in Blacks surpassed that in Whites. These increases occurred despite clinical trials demonstrating the superiority of cytotoxic-containing immunosuppressive regimens over corticosteroids alone. This suggests decreased access to care and/or decreased efficacy of these therapies for lupus nephritis in Black Americans.
Fig. 1 Incidence of ESRD due to Lupus Nephritis in Blacks vs. Whites in U.S., 1995-2004

Disclosure Block: S. Gabriel, None; C.S. Crowson, None; H. Maradit Kremers, Pfizer, 2; Amgen, 5; Amgen, 2; T.M. Therneau, None.

Source: American College of Rheumatology (ACR)