Iron Overload Disorders Among Hispanics -- San Diego, California, 1995

Approximately 1.5 million persons in the United States are affected by iron overload diseases, which are primarily caused by hereditary hemochromatosis -- the most common genetic disorder in the United States (1). Hereditary hemochromatosis is characterized by increased iron absorption in the gastrointestinal tract, which may cause lifelong excessive iron absorption and accumulation and serious health effects, including arthritis, cirrhosis, diabetes, impotence, heart failure, and death (2). Hereditary hemochromatosis is an autosomal recessive disease; the estimated prevalence of the homozygous genotype is 1:200-1:250 persons, and 10% of persons are carriers (3). Although the disease was previously believed to affect primarily white males of northern European descent, recent data indicate hereditary hemochromatosis also occurs among blacks (2,4). Moreover, iron overload diseases are underdiagnosed among whites and may not be considered in other racial/ethnic groups (e.g., Hispanics) even when compatible symptoms and clinical findings are present (5,6). As part of a joint demonstration project during August-October 1995 to determine the overall prevalence of iron overload, CDC reviewed data from a health-maintenance organization (HMO) in San Diego, California; the prevalence among Hispanics * appeared similar to that for non-Hispanic whites. This report presents the preliminary findings of an analysis of the prevalence of iron overload among Hispanics and compares these findings with nationally representative data from the Third National Health and Nutrition Examination Survey (NHANES III). These findings indicate that the prevalence of possible iron overload among Hispanic clients of the HMO based on initial screening was consistent with the nationwide prevalence of possible iron overload based on a single screening test for Hispanics of Mexican descent and non-Hispanic whites (Table_1).

The demonstration project included screening for iron overload among all persons aged greater than or equal to 18 years who were newly entering the HMO's medical program during August-October 1995 (n=15,000). The transferrin saturation (TS) test (serum iron/total iron binding capacity X 100) was used to identify abnormal iron metabolism (normal=30%). Preliminary findings indicated that an elevated TS was detected in 420 (2.8%) of the 15,000 persons screened. In comparison, based on NHANES III, ** the prevalence of elevated TS among non-Hispanic whites was 1.6% and among Hispanics of Mexican descent was 1.5% (Table_1). The 420 persons with elevated TS subsequently received a complete medical examination, follow-up TS, and phlebotomy to confirm the diagnosis of iron overload.

Based on this evaluation, iron overload was diagnosed or confirmed in 60 persons, representing a prevalence of 4.0 cases per 1000 persons screened. Of these 60 persons, 10 (16.7%) reported their ethnicity as Hispanic. The HMO's records indicated that 13.1% of its total population reported their ethnicity as Hispanic; therefore, the prevalence of iron overload among Hispanic patients was five cases per 1000 Hispanic patients.

Reported by: V Felitti, MD, M Perlman, MD, N Howard, Kaiser Permanente Medical Care Program, San Diego, California. Maternal and Child Health Br, Div of Nutrition and Physical Activity, National Center for Chronic Disease Prevention and Health Promotion; Nutritional Statistics Br, Div of Health Examination Statistics, National Center for Health Statistics; Div of Birth Defects and Developmental Disabilities, and Div of Environmental Health Laboratory Sciences, National Center for Environmental Health, CDC.

Editorial Note

Editorial Note: The gene that may cause most cases of hereditary hemochromatosis has been identified (7). However, the potential role of variations of this gene and genetic variations at other loci in causing hereditary hemochromatosis among different population subgroups, such as Hispanics described in this report, have not been determined (4). Until a test to detect the gene(s) that causes hereditary hemochromatosis is developed, clinicians and public health practitioners must rely on the phenotypic expression of abnormal iron metabolism for screening and case detection.

Recent findings suggest that the prevalence of iron overload diseases is more common than previously believed (2,3). Screening with TS and early treatment for iron overload diseases are the principal strategies for preventing development of chronic diseases in persons who are homozygotes for the gene. Treatment with periodic phlebotomy can remove excess iron before organ damage occurs and can substantially reduce morbidity and mortality from the associated chronic diseases (2,6,8). Systematic screening with TS and case detection also can reduce health-care costs associated with these diseases (2,9).

References

1. McLaren CE, Gordeuk VR, Looker AC, et al. Prevalence of heterozygotes for hemochromatosis in the white population of the United States. Blood 1995;86:2021-7.

2. College of American Pathologists. Practice parameters for hereditary hemochromatosis. Clin Chim Acta 1996;245:139-200.

3. Edwards CQ, Griffen LM, Goldgar D, Drummond C, Skolnick MH, Kushner JP. Prevalence of hemochromatosis among 11,065 presumably healthy blood donors. N Engl J Med 1988;318:1355-62.

4. Barton J, Edwards CQ, Bertoli LF, Shroyer TW, Hudson SL. Iron overload in African Americans. Am J Med 1995;99:616-23.

5. Rouault TA. Hereditary hemochromatosis. JAMA 1993;269:3152-4.

6. Edwards CQ, Kushner JP. Screening for hemochromatosis. N Engl J Med 1993;328:1616-20.

7. Feder JN, Gnirke A, Thomas W, et al. A novel MHC class I-like gene is mutated in patients with hereditary hemochromatosis. Nature Genetics 1996;13:399-408.

8. Niederau C, Fischer R, Sonnenberg A, Stremmel W, Trampisch HJ, Strohmeyer G. Survival and causes of death in cirrhotic and in noncirrhotic patients with primary hemochromatosis. N Engl J Med 1985;313:1256-62.

9. Phatak PD, Guzman G, Woll JE, Robeson A, Phelps CE. Cost-effectiveness of screening for hereditary hemochromatosis. Arch Intern Med 1994;154:769-76.

* In this report, persons who reported their origin as Hispanic of Mexican descent or Filipino were categorized as Hispanic. Persons of Hispanic origin can be of any race.

** Data from NHANES III are based on a single elevated TS test indicating an initial positive screening; no follow-up analysis was conducted.

TABLE  1.  Prevalence of possible iron overload * among non-Hispanic whites and
Hispanics of Mexican descent aged >=20 years, by sex -- United States, Third
National Health and Nutrition Examination Survey (NHANES III), 1988-1994
=========================================================================================
                            Sample
Characteristic                size        %   (95% CI +)
-----------------------------------------------------------------------------------------
Non-Hispanic white
Men                           3168      1.4      (0.9%-1.9%)
Women                         3648      1.8      (1.1%-2.5%)
Total                         6818      1.6      (1.1%-2.1%)

Hispanics of Mexican
descent
Men                           2172      2.0      (1.2%-2.7%)
Women                         2171     0.9&      (0.2%-1.6%)
Total                         4343      1.5      (0.9%-2.0%)
-----------------------------------------------------------------------------------------
* Based on an initial elevated transferrin saturation (TS) (55% for women and 60% for
  men).
+ Confidence interval
& May be unreliable. NHANES III is a multipurpose health survey that was not designed to
  yield prevalence estimates of <10%.  However, because of the public health importance
  of hemochromatosis, the usual criteria for presentation of prevalences from NHANES were
  relaxed.
=========================================================================================

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