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Researchers study screening for hemochromatosis in primary care
Hemochromatosis is a common and treatable genetic disease characterized by excessive absorption of dietary iron. It affects 2 to 5 of every 1,000 people in the United States and may cause tissue damage and dysfunction of the liver, pancreas, heart, and pituitary gland. A gene for hemochromatosis was discovered in 1996, but many questions remain about the accuracy of genetic testing for this condition. Interest in including screening for hemochromatosis using serum transferrin saturation testing (even without DNA test results) in the routine medical care of adults has grown in recent years. The goal of screening programs is to diagnose iron status disorders, particularly hemochromatosis, before they lead to iron overload and chronic disease states.
Two recent papers, resulting from a study supported by the Agency for Health Care Policy and Research (HS07616), examine the prevalence of hereditary hemochromatosis among primary care patients and the practical issues involved when iron status screening for hemochromatosis is implemented. The AHCPR-supported study was led by Pradyumna D. Phatak, M.D., of the University of Rochester School of Medicine and Dentistry. The two papers are summarized here.
Phatak, P.D., Sham, R.L., Raubertas, R.F., and others (1998, December). "Prevalence of hereditary hemochromatosis in 16,031 primary care patients." Annals of Internal Medicine 129(11), pp. 954-961.
This study of 22 primary care practices in Rochester, NY, examined the prevalence of hemochromatosis among 16,031 outpatients without a previous diagnosis of the condition. The researchers screened patients with serum transferrin saturation screening tests and offered liver biopsies to confirm the diagnosis. The prevalence of clinically proven and biopsy-proven hemochromatosis combined was 4.5 per 1,000 people in the total sample and 5.4 per 1,000 in white patients. Twice as many men were diagnosed with hemochromatosis as women.
Diagnosis of hemochromatosis is routinely followed by the screening of first-degree relatives, but routine screening for hemochromatosis in primary care is not recommended at this time. However, given the high prevalence of undiagnosed hemochromatosis among whites, these researchers recommend routine primary care screening with serum transferrin saturation testing in this population. They point out that the degree of iron overload in many of these patients suggested that irreversible damage would have occurred if the disease had gone unrecognized and tissue iron stores had continued to accumulate.
McDonnell, S.M., Phatak, P.D., Felitti, V., and others (1998, December). "Screening for hemochromatosis in primary care settings." Annals of Internal Medicine 129(11), pp. 962-970.
In this paper, the researchers assert that because of its availability, low cost, high sensitivity, and acceptable specificity, the transferrin saturation test is currently the most appropriate initial screening test for hemochromatosis. They address practical issues encountered by four hemochromatosis screening programs that need to be addressed when implementing iron status screening. These include changes in case definitions of hemochromatosis from the classic description, selection of screening threshold values and identification of false-positive cases, variability and lack of standardization of screening test measurements, physician education, informed consent and concerns about medical and genetic discrimination, patient compliance with screening and therapy, and incidental detection of iron deficiency.
For instance, the genetic tests and even biochemical criteria for early diagnosis of hemochromatosis are new and not yet fully correlated with clinical outcomes. A lower threshold of iron saturation should probably be used for women and blacks—two groups that have less incidence of
hemochromatosis than white men—thus capturing more of the disease. However, lower cut-points have not been directly tested for their association with the newly described genetic mutations or clinical outcomes. Many physicians are unconvinced that hemochromatosis exists in their patient population and are unfamiliar with the transferrin saturation test. The health consequences of hemochromatosis can largely be prevented with early detection. But ethical, patient consent, and confidentiality issues regarding testing remain.
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