Iron Loading and Disease Surveillance.

To the Editor: We read with interest the article by E. D. Weinberg entitled "Iron Loading and Disease Surveillance" (1). Dr. Weinberg proposes routine population screening of iron values by serum ferritin and transferrin saturation tests. Such screening could provide valuable information for epidemiologic, diagnostic, prophylactic, and therapeutic studies of emerging infectious diseases. However, population screening for hereditary hemochromatosis, the example Dr. Weinberg uses to illustrate his proposal, should await additional data (2-4). At; this time, it is not known how many people with genetic risk or biochemical evidence of iron overload will actually become ill. Therefore, the benefits of screening cannot be weighed against the risks of unnecessary treatment. Moreover, standardized, reliable methods for measuring and diagnosing iron overload are not available.

Without additional data, population screening can actually be detrimental to those at risk for disease. Persons with hereditary hemochromatosis may face discrimination, including difficulties in acquiring health, life, or disability insurance. Already, current blood safety policy makes it difficult for them to donate blood, even though blood donation is unlikely to have negative consequences. In addition, the costs of screening for hemochromatosis are not routinely covered by medical insurance nor has the cost-effectiveness of screening been determined. If routine screening is adopted, tracking of persons who test positive must be developed to ensure that appropriate and continuing follow-up is provided and patient confidentiality is preserved.

The Centers for Disease Control and Prevention recommends testing for persons who have either a close relative with hemochromatosis or who themselves experience the unexplained symptoms compatible with the disease (severe weakness or fatigue; unexplained joint or abdominal pain) or its later complications (liver disease, diabetes, or heart problems; impotence; infertility; loss of menstrual periods) (2,5). Testing to exclude other causes of these medical problems should also be performed. Persons with elevated iron or liver function measures should be monitored by their health-care provider.

Michele Reyes and Giuseppina Imperatore Centers for Disease Control and Prevention, Atlanta, Georgia, USA

References

(1.) Weinberg ED. Iron loading and disease surveillance. Emerg Infect Dis 1999;5:346-52.

(2.) Cogswell ME, Mc Donnell SM, Khoury MJ, Franks AL, Burke W, Brittenham G. Iron overload, public health, and genetics: evaluating the evidence for hemochromatosis screening. Ann Intern Med 1998;129(Suppl 11);971-9.

(3.) Cogswell ME, Burke W, McDonnell SM, Franks AL. Screening for hemochromatosis. A public health perspective. Am J Prev Med 1999; 16:134-40.

(4.) EASL International Consensus Conference on Haemochromatosis. J Hepatol 2000;33:485-504.

(5.) Witte DL, Crosby WH, Edwards CQ, Fairbanks VF, Mitros FA. Practice guideline development task force of the College of American Pathologists. Hereditary hemochromatosis. Clin Chim Acta 1996;245:139-200.

Reply to Dr. Reyes

To the Editor: The article noted that nearly 50 microbial genera contain strains that are more pathogenic in iron-loaded than in normal hosts. The article proposed "routine screening of populations exposed to certain diseases" but not routine screening of populations at large. A few examples of current interest include atherosclerosis (Coxiella and Chlamydia), septicemia (Capnocytophaga), Whipple's disease (Tropheryma), tuberculosis (Mycobacterium), gastric ulcers (Helicobacter), hepatitis (hepatitis C), and AIDS (opportunistic pathogens).

Of course, the tissue or cell localization of iron and the possible pathogen must be considered. For instance, Legionella multiplies in iron-loaded alveolar macrophages but not in plasma. Thus, it would be expected that persons with untreated hemochromatosis with minimal macrophage iron but with high plasma iron would not be at risk for Legionnaires' pneumonia.

Eugene D. Weinberg Indiana University, Bloomington, Indiana