More than 200,000 people in US meet criteria for systemic lupus erythematosus
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More than 200,000 people in the United States met the American College of Rheumatology criteria for systemic lupus erythematosus in 2018, according to data published in Arthritis & Rheumatology.
The findings represent the first national estimate of SLE prevalence in the United States since the CDC established several registries to track the disease more than 10 years ago, read a press release announcing the data.
“Previous estimates for SLE rates in the United States (US) have been predominantly derived from tertiary care settings and relatively small, homogeneous patient populations that contain limited data on key demographic groups in the U.S.,” Peter Izmirly, MD, of NYU Langone Health, and colleagues wrote. “Other explanations for the varied estimates, which range from 19 to 241 per 100,000, include racial/ethnic disparities in SLE susceptibility and mortality, differing case definitions, heterogeneous sources for case ascertainment, small populations, possible inaccuracy of self-report, unreliability in coding in health system databases, and variable access to health care for high-risk populations.”
“The (CDC) funded a network of five population-based SLE registries, each using similar active surveillance methods, to determine SLE incidence and prevalence in populations reflecting a broad distribution of racial/ethnic demographics in the U.S.,” they added. “Data from these five registries have provided overall prevalence and incidence rates of SLE, as well as estimates that focused on the major U.S. demographic groups, including whites and Blacks, Asians/Pacific Islanders and Hispanics and American Indians/Alaska Natives (AI/AN).”
To estimate the prevalence of SLE in the United States, Izmirly and colleagues conducted a meta-analysis of the CDC National Lupus Registry networks in Georgia, Michigan, California and New York, as well as the Indian Health Service, which collects data from Alaska, Arizona and Oklahoma. All five registries used the 1997 revised ACR classification criteria for the SLE.
Focusing on the time periods of 2002-2004 or 2007-2009, the researchers identified a total of 5,417 cases that fulfilled the classification criteria. They then calculated the number of people with SLE for every gender and ethnic group, and applied those demographic numbers to national population statistics from the 2018 U.S. Census.
According to the researchers, the pooled, nationwide prevalence, based on the four state-specific registries, was 72.8 per 100,000 people (95% CI, 65.3-81.0). Based on 2018 U.S. Census figures, the researchers concluded that 204,295 individuals (95% CI, 160,902-261,725) in the United States meet the ACR SLE criteria.
The prevalence of SLE in the four state-specific registries was nine times higher for women, at 128.7, than men, at 14.6, and was highest among Black women, who demonstrated a prevalence of 230.9, followed by Hispanic women — 120.7 — white — 84.7 — and Asian/Pacific Islander — 84.4. Among men, prevalence was highest in Black individuals, at 26.7, followed by Hispanic men at 18, Asian/Pacific Islander men at 11.2 and white men at 8.9.
However, the highest prevalence was found in the Indian Health Service registry. According to the researchers, American Indians and Alaska Natives together demonstrated the highest race-specific SLE estimates for women, at 270.6, and men, at 53.8.
“I think the importance of this work is that is provides accurate prevalence estimates for systemic lupus erythematosus among the major racial/ethnic demographics in the United States,” Izmirly told Healio Rheumatology. “I think the key takeaways are that our estimates for SLE approach the FDA’s definition or a rare disease, and the clinical significance is that SLE disproportionally affects women and racial minorities. Women are nine times more likely than men to be affected with SLE, and American Indian and Alaska Native women, as well as Black women, had the highest race-specific lupus estimates.”
Perspective
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In presenting their meta-analysis on U.S. lupus prevalence, Izmirly and colleagues unwrap what is, to date, the definitive portrait of SLE epidemiology across several representative regions nationally. Many of the same investigators participated in the prior registry studies, published previously in two pairs of articles in the same journal in 2014 and 2017; these provided data representing urban/suburban Michigan and Georgia, San Francisco and NYC (Manhattan.)
In the current study, they have added similarly-derived information from the Indian Health Service, encompassing Oklahoma City, Phoenix and Alaska. Their methods were remarkably consistent across the disparate locations, producing an admirable uniformity of results.
For case definition, they used the 1997 revised ACR classification criteria, but in their case finding also recognized multiple sources and techniques. For simplicity and clarity, they did not utilize the 2012 SLICC or more recent ACR/EULAR 2017 criteria, as the work began in 2002.
The analysis yielded results demonstrating SLE to be perhaps a rarer disorder than widely assumed, 72.8 per 100,000 population (2002-2009) — less than 0.1% prevalence — and reasserts the oft-quoted 9:1 female to male ratio with remarkable consistency. Many more of the specific gender and race-based findings replicate what we clinicians are accustomed to observing; among these, it behooves us to note high disease incidence in the Native American populations, and in males.
Several factors may underlie the unexpected rarity of SLE prevalence: The lack of inclusion of incomplete or undifferentiated lupus/CTD, pure discoid/cutaneous lupus and drug-induced disease. While the investigators’ figures were applied to a more updated census denominator to calculate total SLE cases, we must acknowledge that this likely represents an underestimation, given that over time the incidence and prevalence of lupus are acknowledged to be steadily increasing, and for this, health services will need to be planned.
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