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Effect of Ethnicity on Disease Activity in Systemic Lupus Erythematosus
To the Editor: We read the recent article by Ghaussy and colleagues, comparing disease activity in patients with systemic lupus erythematosus (SLE) from 2 different ethnic groups, Hispanics and Caucasians from New Mexico1. Our observations about it are the result of our combined experience with Hispanic patients with SLE from Texas (mainly of Mexican ancestry), from Puerto Rico, and from Spain, as well as from our interpretation of the literature2. A major concern in our view is that no information is provided about the ethnic background of the Hispanic patient subset studied. As we know, the Hispanic population in the US is heterogeneous (although language and culture are shared)3. There are, however, fundamental differences among various Hispanic subgroups; this variability is best expressed as differences in the estimated admixture proportions [Spaniard (European), Amerindian, and African] among the Hispanic subgroups4. Second, important differences in the clinical characteristics of SLE and its outcome among various Hispanic subgroups have been reported by our group5 and by investigators from GLADEL, a Latin American consortium for the study of lupus, which is prospectively recruiting and following SLE patients from different South and Central American countries2. Moreover, we have prospectively compared a group of Spaniard patients with SLE and our Hispanic (Mexican ancestry) LUMINA patients, and found them to have a milder disease with lower levels of disease activity over time, suggesting that the larger the Amerindian genetic pool, the greater the severity of the disease among Hispanic patients6. These data taken together suggest that it is critical to properly define the Hispanic subgroup studied before reaching conclusions that may not be valid beyond the patients in which the data were generated. Indeed, we suspect that the negative findings from the study may relate to the higher Spanish (European) background in the Hispanic patients those authors have studied than in our Hispanic LUMINA patients. A third issue of concern relates to the relatively long disease duration of the patients studied; although disease duration was comparable in their Hispanic and Caucasian patients (7.60 vs 9.25 years) and it was adjusted for in the analyses, it is known that disease activity in lupus generally wears off over time, the first few years showing more active disease, when the large majority of severe clinical manifestations occur. Thus, studying patients later in their course may have precluded these investigators detecting differences in disease activity that may have been present earlier in the disease course; further, it is well known that disease activity may portend a poor prognosis, as we and others have shown7,8, so these investigators could have assessed damage as indirect evidence that disease activity was in fact comparable earlier, but this was not done. Fourth, although the authors refer to having studied a representative sample of their patients, the sampling frame is not provided. Moreover, by design they have excluded patients with disease severe enough to cause death shortly after onset, and numbers of deaths may have been unbalanced in the 2 groups; however, that cannot be concluded from the data presented. Finally, while we agree that smoking is a toxic habit that may affect SLE, it cannot be categorized as abnormal illness behavior. The construct of abnormal illness-related behaviors as measured by the Illness Behavior Questionnaire9 refers to how patients cope with an illness and not to unhealthy behaviors such as smoking or drinking; indeed, our group has recently reported that abnormal illness-related behaviors may negatively influence disease activity in SLE10. In short, it seems to us that the authors have reached conclusions that may not be applicable to the large number of Hispanic US patients with SLE. JAIME CALVO-ALÉN, MD, The University of Alabama at Birmingham Birmingham, Alabama; LUIS M. VILÁ, MD, The University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico; JOHN D. REVEILLE, MD, The University of Texas-Houston Health Sciences Center, Houston, Texas; GRACIELA S. ALARCÓN, MD, MPH, The University of Alabama at Birmingham, Birmingham, Alabama, USA. REFERENCES 1. Ghaussy NO, Sibbitt WL Jr, Bankhurst AD, Qualls CR. The effect of race on disease activity in systemic lupus erythematosus. J Rheumatol 2004;31:915-9. 2. Pons-Estel BA, Catoggio LJ, Cardiel MH, et al. The GLADEL multinational Latin American prospective inception cohort of 1,214 patients with systemic lupus erythematosus: ethnic and disease heterogeneity among "Hispanics". Medicine 2004;83:1-17. 3. Borak J, Fiellin M, Chemerynski S. Who is Hispanic? Implications for epidemiologic research in the United States. Epidemiology 2004;15:240-4. 4. Reveille JD, Beasley TM, Tan FK, et al. Admixture as a measure of genomic control. Data from a multiethnic lupus cohort [abstract]. Arthritis Rheum 2003;48 Suppl:S225. 5. Vilá LM, Alarcón GS, McGwin G Jr, et al. Early clinical manifestations, disease activity and damage of systemic lupus erythematosus among two distinct US Hispanic subpopulations. Rheumatology Oxford 2004;43:358-63. 6. Calvo-Alén J, Reveille JD, Rodríguez-Valverde V, et al. Clinical, immunogenetic and outcome features of Hispanic systemic lupus erythematosus patients of different ethnic ancestry. Lupus 2003;12:377-85. 7. Alarcón GS, McGwin G Jr, Bartolucci AA, et al. Systemic lupus erythematosus in three ethnic groups. IX. Differences in damage accrual. Arthritis Rheum 2001;44:2797-806. 8. Stoll T, Stucki G, Malik J, Pyke S, Isenberg DA. Association of the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index with measures of disease activity and health status in patients with systemic lupus erythematosus. J Rheumatol 1997;24:309-13. 9. Pilowsky L, Spence ND. Illness behavior questionnaire. In: Corcoran K, Fischer J, editors. Measures for clinical practice: a source book. New York: The Free Press; 1996:182-5. 10. Calvo-Alén J, Uribe A, McGwin G Jr, Reveille JD, Alarcón GS. Persistently active disease early in the course of systemic lupus erythematosus is associated with sociodemographic factors and portends a poor prognosis (damage accrual). Proceedings of the VII International Congress of Systemic Lupus Erythematosus and Related Conditions, New York, NY. May 9-13, 2004. |