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Dr. Ghaussy, et al, reply: Effect of Ethnicity on Disease Activity in Systemic Lupus Erythematosus
To the Editor: We thank Dr. Calvo-Alén and colleagues for their interest in our study. We defined ethnicity as 4 grandparents of the same ethnic background, as defined in other studies1. After our study had been completed, several reports were published suggesting that there are important differences in the clinical characteristics of systemic lupus erythematosus (SLE) among various Hispanic subgroups2-4. As we stated in our discussion, this was one possible explanation why we did not find a significant difference in overall disease activity between Hispanics and Caucasians, as the majority of our Hispanic population had a Spanish background rather than a strictly Mexican ancestry. We believe our study gives additional support for the findings of Dr. Calvo-Alén, et al, that there are fundamental differences among various Hispanic subgroups; and we agree that future studies regarding Hispanics should provide information about the ethnic background of the Hispanic patient subset. The following 2 paragraphs are part of a discussion addressed to a reviewer in August 2003 regarding the complex history of New Mexican Hispanics. As to the Hispanic ethnic makeup of New Mexico, it is somewhat complex. The earliest Spaniards in New Mexico came as soldiers without women; thus, the children of these soldiers were of mixed Amerindian and Spanish blood. However, the next generation saw a large influx of Spanish settlers including women; thus, there are many communities where there is largely Spanish (Mediterranean-European) blood with very little Amerindian blood. These are the people who call themselves "Spanish" in New Mexico. However, this is complicated by the fact that the Spanish settlers were accompanied by "Spanish" soldiers and laborers, many of whom were actually Indians recruited from the villages around Mexico City; thus, certain of the communities in New Mexico had considerable Indian blood. Finally, in the last 150 years there has been considerable Mexican immigration to New Mexico, particularly to the southern part of New Mexico. Cinco de Mayo, Mexican Independence Day, is a big celebration in southern New Mexico, but is unimportant in northern New Mexico because northern New Mexicans have no historical connection with the Mexican Revolution of Juarez. Thus, the northern New Mexicans actually are more "Spanish" than the southern New Mexicans, who tend to be more Mexican culturally and genetically. There are also language differences that reflect this; northern New Mexico speaks a dialect very close to 16th and 17th century Spanish rather than the more or less contemporary Mexican Spanish spoken in the south. Thus our population in this study was predominately northern New Mexican and was roughly 75% European-Mediterranean blood and 25% Amerindian blood. Our study design, a case controlled study, has certain limitations and potentials for bias that are well known. Although not presented in this study, we did not find any significant difference in overall cumulative organ damage as measured by the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index among the New Mexico Hispanic and Caucasian population with SLE. It is noted that the Illness Behavior Questionnaire does not consider smoking as an abnormal illness-related behavior. Cigarette smoking has been shown to be associated with increased disease activity in SLE, even after adjusting for ethnicity, as well as various aspects of SLE activity and outcome5-9. We believe a detailed smoking history should be included and adjusted for when comparing disease activity and outcomes in SLE. We appreciate the valuable insights of Dr. Calvo-Alén and colleagues and their significant contributions to the scientific literature. NAJEEB GHAUSSY, MD; WILMER L. SIBBITT Jr, MD; ARTHUR D. BANKHURST, MD, Departments of Internal Medicine, Rheumatology, Neurology, Mathematics and Statistics, and Epidemiology, and the Clinical and Magnetic Research Center, Albuquerque, New Mexico, USA. REFERENCES 1. Reveille JD, Moulds JM, Ahn C, et al. Systemic lupus erythematosus in three ethnic groups. I. The effects of HLA Class II, C4, and CR1 alleles, socioeconomic factors, and ethnicity at disease onset. Arthritis Rheum 1998;41:1161-72. 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. Vila LM, Alarcon 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. 4. Calvo-Alén J, Reveille JD, Rodriguez-Valverde V, et al. Clinical, immunogenetic and outcome features of Hispanic systemic lupus erythematosus patients of different ethnic ancestry. Lupus 2003;12:377-85. 5. Ghaussy NO, Sibbitt WL Jr, Bankhurst AD, Qualls CR. Cigarette smoking and disease activity in systemic lupus erythematosus. J Rheumatol 2003;30:1215-21. 6. Petri M. Smoking is a risk factor for musculoskeletal, pulmonary, and cardiac disease in systemic lupus erythematosus [abstract]. Arthritis Rheum 1997;40 Suppl:S118. 7. Rahman P, Gladman DD, Urowitz MB. Smoking interferes with efficacy of antimalarial therapy in cutaneous lupus. J Rheumatol 1998;25:1716-9. 8. Brown K, Petri M, Goldman D. Cutaneous manifestations of systemic lupus erythematosus: associations with other manifestations of SLE and with smoking [abstract]. Arthritis Rheum 1995;38 Suppl:R27. 9. Ward MM, Studenski S. Clinical prognostic factors in lupus nephritis. Arch Intern Med 1992;152:2082-8. |