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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptNIH Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
Arthritis Rheum. Author manuscript; available in PMC Sep 5, 2008.
Published in final edited form as:
PMCID: PMC2530907
NIHMSID: NIHMS18176

Prevalence of Adult Systemic Lupus Erythematosus in California and Pennsylvania in 2000: Estimates Using Hospitalization Data

Eliza F. Chakravarty, M.D., M.S.
Division of Immunology and Rheumatology, Department of Medicine; Stanford University School of Medicine, Stanford
Thomas M. Bush, M.D.
Division of Rheumatology, Department of Medicine; Santa Clara Valley Medical Center, San Jose, CA
Susan Manzi, M.D., M.P.H.
Division of Rheumatology, Department of Medicine and Department of Epidemiology; University of Pittsburgh, Pittsburgh, PA
Ann E. Clarke, M.D., M.Sc.
Divisions of Clinical Immunology/Allergy and Clinical Epidemiology, Montreal General Hospital, McGill University Health Centre, Montreal, Quebec, Canada.
Michael M. Ward, M.D., M.P.H.

The prevalence of systemic lupus erythematosus (SLE) in the United States is not known. The estimates that are available have been based on populations in small geographic areas with unique demographic characteristics, or on telephone surveys [1]. These estimates range widely from 5.8 to 1000 per 100,000 people [1-3]. Having current nationally representative estimates of the prevalence of SLE would increase our understanding of the burden of disease and help in health care planning.

We applied a new method that combines data on the frequency with which patients are hospitalized with data from state inpatient hospital databases to estimate the prevalence of SLE in adults (aged 18 or older) in California and Pennsylvania [4]. California, through its Office of Statewide Health Planning and Development, and Pennsylvania, through the Health Care Cost Containment Council, mandate that hospitals report discharge abstracts for each hospitalization annually. Abstracted data include patient age, sex, race, and discharge diagnoses (up to 25 in California, up to 8 in Pennsylvania), as well as encrypted unique patient identifiers to identify individuals with multiple hospitalizations. From these databases, we identified the number of adults in each state who had a hospitalization in 2000 that included SLE among their discharge diagnoses. Dividing these numbers by the proportion of patients with SLE who are hospitalized each year provides an estimate of the number of patients with SLE in each state. Prevalence was then calculated by dividing this number by the state populations in the 2000 U.S. census. Prevalence estimates were age, sex, and race/ethnicity-adjusted to the structure of the population in the 2000 U.S. census by direct standardization. Prevalences were calculated separately for each state.

Data on the proportion of patients with SLE hospitalized annually were obtained by medical record review of all patients with SLE (N = 415) followed routinely at one of two medical centers in northern California: Stanford University Hospital and Clinics, and Santa Clara Valley Medical Center, a public medical center serving the county of Santa Clara. In addition, annual hospitalization data were obtained by self-report of 117 patients with SLE in Pennsylvania enrolled in an observational study of health care use from 1996 through 2001 [5,6]. All patients met ACR criteria for the classification of SLE [7]. Data on gender and age (18-44 years, 45-64 years, and 65 years or greater) and ethnicity was collected for each patient. Emergency department visits that did not result in a hospital admission were excluded as they are not captured in the inpatient hospital databases.

Overall hospitalization frequencies were 28% in California and 22% in Pennsylvania. Among California patients, hospitalization frequency was significantly higher among women aged 65 years or older (63%) than for all other demographic subgroups (28%). The smaller number of Pennsylvania patients did not permit analysis of hospitalization frequencies in subgroups by gender, age, and ethnicity.

The overall age, gender, and race/ethnicity adjusted prevalence per 100,000 persons aged 18 years and older was 107.6 (95% CI 106.1-109.2) in California and 149.5 (95% CI 146.9-152.2) in Pennsylvania. Prevalence estimates for each state by gender, race/ethnicity and age group are listed in the Table. Women had a higher prevalence than men with a ratio of approximately 7:1. Because of small numbers of men with SLE, rates in demographic subsets were not examined. Among women, blacks had a higher prevalence of lupus by 2.5 to 3.5-fold compared to whites. Asian/Pacific Islander women appeared to have the lowest prevalence of SLE.

To examine the influence of differences in hospitalization frequencies on the differences in prevalence estimates between California and Pennsylvania, we repeated the analyses applying the hospitalization frequencies from California to the Pennsylvania hospital discharge data. This resulted in a prevalence estimate in Pennsylvania of 104.3 (95% CI 102.1-106.6) per 100,000 for all adults and 173.3 (95% CI 169.3-177.2) per 100,000 women, which were very similar to estimates in California (107.6 per 100,000 adults, and 184.2 per 100,000 adult women). Similarly, applying the hospitalization frequency of Pennsylvania to the California hospital discharge data resulted in a prevalence estimate of 153.9 (95% CI 152.1-155.7) per 100,000 adults and 266.9 (95% CI 263.6-270.2) per 100,000 women, estimates that were very similar to the Pennsylvania estimates (149.5 per 100,000 adults and 253 per 100,000 adult women). Differences in the hospitalization frequencies led directly to differences in the prevalence estimates between the states, rather than true differences in the prevalence of SLE. The true prevalence likely lies somewhere between these calculated estimates.

Using this new method for estimating state-wide prevalence of chronic diseases that compares hospitalization frequency to state hospitalization databases, we obtained gender, age, and race/ethnicity specific estimates for the prevalence of SLE. Adjusted prevalence estimates obtained from these data range from 107 to 150 per 100,000 persons overall and roughly 1.8-2.5 per 1,000 women. These results fall within the upper bounds of estimates obtained from studies of local populations and within the range of estimates based upon a nationwide study of self-report of physician-diagnosed SLE [1,3]. The prevalence estimates in this study are higher than those reported from Olmsted County, Minnesota [8] and in rural Wisconsin [9], which might be expected given the known predisposition of ethnic minorities to SLE and the relative absence of ethnic minorities in these populations. The close approximation of prevalences estimated through this technique to that reported in the literature is similar to what has been shown for other uncommon chronic diseases [4].

The use of state hospitalization databases does not allow for verification of diagnoses of SLE, but these estimates are based on physician (not necessarily rheumatologist) diagnosis. Undercounting in the state databases is unlikely given the large number of available fields for coding discharge diagnoses. More accurate estimates would be obtained using hospitalization frequencies from a population-based sample of patients with SLE, but such data are not available. However, we obtained similar estimates (22-28% of patients hospitalized annually) using two separate cohorts of patients: consecutive patients followed by academic as well as community-based rheumatology clinics in northern California, and self-reported hospitalization data obtained from subjects participating in a longitudinal study of SLE; suggesting that our estimates may approximate true annual hospitalization frequencies among adults with SLE. It is important to emphasize that these prevalence estimates apply to persons age 18 years and older. If children had been included, these estimates would be approximately 25% lower, based on the proportion of children in each state (27.3% in California and 23.8% in Pennsylvania). Given that our prevalence estimates reflect a broader demographic range than previous studies and represent samples from two populous states, these rates may be considered current nationwide estimates for the prevalence of adult SLE.

Table thumbnail
Table: Prevalence estimates of adult SLE per 100,000 persons

Footnotes

Sources of support: This research was supported in part by the Intramural Research Program of the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health (M. Ward), Fonds de la recherche en sante du Quebec and the Arthritis Society of Canada. Dr. Clarke is a Quebec National Research Scholar (A. Clarke); and NIH 5 R01 AR46588-05, NIH 5 K24 AR002213-05, PA Department of Health (S. Manzi).

References

1. Ward MM. Prevalence of physician-diagnosed systemic lupus erythematosus in the United States: results from the third National Health and Nutrition Examination Survey. Journal of Women’s Health. 2004;6:713–8. [PubMed]
2. Petri M. Epidemiology of systemic lupus erythematosus. Best Practice and Research Clinical Rheumatology. 2002;16:847–58. [PubMed]
3. Lawrence RC, Helmick CG, Arnett FC, Deyo RA, Felson DT, Giannini EH, Heyse SP, Hirsch R, Hochberg MC, Hunder GG, Liang MH, Pillemer SR, Steen VD, Wolfe F. Estimates of the prevalence of arthritis and selected musculoskeletal disorders in the United States. Arthritis Rheum. 1998;41:778–99. [PubMed]
4. Ward MM. Estimating rare disease prevalence from administrative hospital databases. Epidemiology. 2005;16:270–1. [PubMed]
5. Clarke AE, Petri MA, Manzi S, Isenberg DA, Gordon C, Senecal JL, St Pierre Y, Joseph L, Penrod J, Fortin PR, Sutcliffe N, Goulet JR, Choquette D, Grodzicky T, Danoff DS, Ho V, Esdaile JM. An international perspective on the well being and health care costs for patients with systemic lupus erythematosus. Tri-Nation Study Group. J Rheumatol. 1999;26:1500–11. [PubMed]
6. Clarke AE, Petri M, Manzi S, Isenberg DA, Gordon C, Senecal J-L, Penrod J, Joseph L, St. Pierre Y, Fortin PR, Sutcliffe N, Goulet JR, Choquette D, Grodzicky T, Esdaile JM. The systemic lupus erythematosus Tri-nation Study: absence of a link between health resource use and health outcome. Rheumatology. 2004;43:1016–1024. [PubMed]
7. Hochberg MC. Updating the American College of Rheumatology revised criteria for the classification of systemic lupus erythematosus. Arthritis Rheum. 1997;40:1725. [PubMed]
8. Uramoto KM, Michet CJ, Thumboo J, Sunku J, O’Fallon WM, Gabriel SE. Trends in the incidence and mortality of systemic lupus erythematosus, 1950-1992. Arthritis Rheum. 1999;42:46–50. [PubMed]
9. Naleway AL, Davis ME, Greenlee RT, Wilson DA, McCarty DJ. Epidemiology of systemic lupus erythematosus in rural Wisconsin. Lupus. 2005;14:862–6. [PubMed]
10. Fessel WJ. Systemic lupus erythematosus in the community; incidence, prevalence, outcome, and first symptoms; the high prevalence in black women. Arch Intern Med. 1974;134:1027–35. [PubMed]

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