Epidemiologic data for the autoimmune disorder lupus, a condition where the body's own immune system harms healthy cells and tissues, is limited, and this is especially the case for racial and ethnic minorities in the United States.

Using data from the CDC's National Lupus Patient Registry network of population-based lupus registries, the first credible meta-analysis estimating U.S. prevalence of the disease, published in Arthritis and Rheumatology, was performed.

This novel public health lupus network was spearheaded by Charles (Chad) Helmick, M.D., an epidemiologist with CDC's National Center for Chronic Disease Prevention and Health Promotion, and included the University of Michigan as well as several other research sites and state health departments across the country.

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In partnership with Emory University, NYU School of Medicine, Alaska Native Tribal Health Consortium and UC San Francisco, the public health endeavor found that lupus is less prevalent than previously thought to be, posing a potential risk to research funding eligibility.

"When we started this study, a widely cited lupus statistic was that approximately 1.5 million Americans were affected," says Emily Somers, Ph.D., Sc.M., a study author and associate professor of rheumatology and environmental health sciences at the University of Michigan. "Our meta-analysis found the actual prevalence to be slightly more than 200,000: a number that approaches the FDA's definition of a rare disease."

This poses a potential risk to research funding for the disease. Somers adds that lupus would be classified as a 'rare disease' by the FDA if the original threshold had been updated for population growth, thus allowing more incentives for developing additional lupus medications.

In part, this prevalence discrepancy is due to the diverse ways lupus presents itself and the complexity of diagnosing this condition. Previous estimates for lupus in the U.S. have also been derived from differing case definitions, and from relatively small, similar patient populations.

"Because lupus has many symptoms that are like other diseases, more patients and their providers may think they have this autoimmune disease than actually do," says Helmick. "Before definitely diagnosing their patients with lupus, clinicians may want to consult with or refer their patients to a lupus expert—a rheumatologist--to be sure."

According to the meta-analysis, lupus affects nine times more women than men. It also disproportionally affects racial minorities, with much of the disease's weight falling on American Indian and Alaska Native women, who had the highest race-specific lupus estimates for American women (270 of 100,000 women.)

Following American Indian and Alaska Native women were Black and Hispanic women. Asian/Pacific Islander women were found to have similar prevalence rates to white women.

Among men, disease prevalence was highest in Black men, followed by Hispanic, Asian/Pacific Islander and white men.

"This meta-analysis is a culmination of almost two decades of work from a network of five CDC-funded population-based registries and provides prevalence estimates for lupus among the major racial and ethnic demographics in the U.S.," says study author Peter Izmirly, M.D., a rheumatologist at NYU Langone Health.

"Several of the study authors worked with CDC, the National Association of Chronic Disease Directors and the Lupus Foundation of America to develop the National Public Health Agenda for Lupus in 2015, the first of its kind," says Somers, also a member of U-M's Institute for Healthcare Policy and Innovation. "This blueprint outlines key public health priorities and strategies related to lupus awareness, care and research."

Next steps

The research team has come a long way since creating their first population-based registries in the early 2000s, developing long-term studies to learn about lupus in certain geographical areas of the U.S.

"Lupus remains a serious disease with strong disparities by sex, race and ethnicity, but better clinical and public health interventions are helping patients to manage their lupus," says Helmick. "These studies will provide important information on the progression of lupus as well as treatment, health care access, and disparities in outcomes in both adults and children."

Thanks to CDC funding, Somers and her colleagues are actively working on long-term follow-up research now, studying risk factors for disease development and progression.

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Although rare, lupus is serious and can be life threatening.

"This research is critical. It may allow us to differentiate types of lupus, identifying subsets of disease and the appropriate interventions tailored for each," Somers says. "Furthermore, it may provide insights into causes of lupus which will lead to future prevention strategies."

Support for this analysis was provided by cooperative agreements between the New York City Department of Health and Mental Hygiene, the New York University School of Medicine, the Centers for Disease Control and Prevention U01DP006489 and National Institutes of Health UL1TR002240 to the University of Michigan. Data collection was funded under the following cooperative agreements: Georgia Lupus Registry: DP08806, Michigan Lupus Epidemiology and Surveillance Program: DP001441, California Lupus Surveillance Program: A114297, Manhattan Lupus Surveillance Program: DP002827, and Indian Health Service: Interagency agreement award IAA10FED1003070.

Paper Cited: "Prevalence of Systemic Lupus Erythematosus in the United States: Estimates from a Meta-Analysis of the Centers for Disease Control and Prevention National Lupus Registries," Arthritis & Rheumatology. DOI: 10.1002/art.41632