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Screening for Hemochromatosis in Primary Care Settings
- Sharon M. McDonnell, MD, MPH;
- Pradyumna D. Phatak, MD;
- Vincent Felitti, MD;
- Alexander Hover, MD; and
- Gordon D. McLaren, MD
- From the Centers for Disease Control and Prevention, Atlanta, Georgia; Rochester General Hospital, Rochester, New York; Kaiser Permanente Medical Care Program, San Diego, California; St. John's Health System, Springfield, Missouri; and the Veterans Affairs Medical Center and University of North Dakota School of Medicine and Health Sciences, Fargo, North Dakota. Acknowledgments: The authors thank the primary care physicians at Rochester General Hospital, Rochester, New York; Kaiser Permanente, San Diego, California; the Veterans Affairs Medical Center, Fargo, North Dakota; and the Premier Health Plan and St. John's Health Regional Health System, Springfield, Missouri. They also thank the Greene County Public Health Unit and the Greene County Medical Society (particularly Dr. Jim Blaine of Springfield, Missouri); the four screening programs could not have been conducted without their participation and support. They also thank the institutional review board of the Centers for Disease Control and Prevention for its patience and guidance. Grant Support: In part by grant RO1 HS07616 from the Agency for Health Care Policy and Research, the Centers for Disease Control and Prevention, and the Department of Veterans Affairs. Requests for Reprints: Sharon McDonnell, MD, MPH, Epidemiology Program Office, Division of International Health, Mailstop C-08, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30303; e-mail, sem0{at}cdc.gov. Current Author Addresses: Dr. McDonnell: Centers for Disease Control and Prevention, Epidemiology Program Office, Division of International Health, Mailstop C-08, 1600 Clifton Road, Atlanta, GA 30303. Dr. Phatak: Hematology Unit, Mary M. Gooley Hemophilia Center, Inc., and Department of Medicine, Rochester General Hospital, 1425 Portland Avenue, Rochester, NY 14621. Dr. Felitti: Kaiser Permanente Medical Care Program, 7060 Clairemont Mesa Boulevard, San Diego, CA 92111. Dr. Hover: St. John's Health System, 3231 South National Avenue, Springfield, MO 65807. Dr. McLaren: Hematology/Oncology Section, (11/111-H) Veterans Affairs Medical Center, 5901 East 7th Street, Long Beach, CA 90822. Note: This article is one of a series of articles comprising an Annals of Internal Medicine supplement entitled “Iron Overload, Public Health, and Genetics.” To view a complete list of the articles included in this supplement, please view its Table of Contents.
Abstract
Interest in including screening for hemochromatosis in the routine medical care of adults has grown in recent years.In March 1997, at a meeting on iron overload at the Centers for Disease Control and Prevention, the directors of four hemochromatosis screening programs described the major challenges that they faced and the lessons that they learned in implementing their programs. Seven issues were consistently described as important challenges: 1) changes in case definitions of hemochromatosis, 2) selection of screening threshold values and identification of false-positive cases, 3) variability and lack of standardization in screening test measurements, 4) physician education, 5) informed consent and concerns about medical and genetic discrimination, 6) patient compliance with screening and therapy, and 7) incidental detection of iron deficiency. The two programs that have been completed report a prevalence of iron overload from hemochromatosis of 4.2 to 4.5 per 1000 persons screened; this is consistent with findings in the recent literature. All programs report that screening is feasible and propose that hemochromatosis be defined by repeated elevated serum transferrin saturation values (with or without DNA test results) rather than by the clinical outcome of excessive iron in tissue. The goal of screening programs is to diagnose iron status disorders, particularly hemochromatosis, before they lead to iron overload and chronic disease states. Further research is needed on the ability of genetic and phenotypic tests to predict the clinical expression of hemochromatosis. The experiences outlined in this report highlight practical issues that need to be addressed when iron status screening for hemochromatosis is implemented. It is hoped that this information will facilitate similar efforts in other health care settings.
Hemochromatosis is an inherited disease, characterized by excessive absorption of dietary iron, that can lead to progressive iron accumulation in tissues and organ damage [1]. It has been proposed as a candidate for routine screening with measurement of transferrin saturation [1-20]. To evaluate screening as a primary care strategy, four programs in the United States integrated iron status screening, with an emphasis on hemochromatosis, into their routine health care services for adults. In March 1997, at a meeting at the Centers for Disease Control and Prevention, the directors of these four programs described the major challenges that they faced and the lessons that they learned in implementing their programs. Seven issues were consistently reported to need resolution in the implementation of hemochromatosis screening: 1) changes in case definitions of hemochromatosis from the classic description, 2) selection of screening threshold values and identification of false-positive cases, 3) variability and lack of standardization of screening test measurements, 4) physician education, 5) informed consent and concerns about medical and genetic discrimination, 6) patient compliance with screening and therapy, and 7) incidental detection of iron deficiency.
The four programs described here are in different stages of operation and in different settings (Table 1). They are at Rochester General Hospital at the University of Rochester, Rochester, New York; the Kaiser Permanente Medical Care Program, San Diego, California; the Veterans Affairs Medical Center, Fargo, North Dakota; and St. John's Health System, Springfield, Missouri.
Changes in Case Definitions of Hemochromatosis
The definition of hemochromatosis has traditionally been based on late clinical and pathologic findings of iron overload [1], and the diagnosis has typically been made by excluding other conditions (such as secondary iron overload or primary liver disease) and finding characteristic pathologic evidence on liver biopsy [21]. Recently, as a result of increased emphasis on early diagnosis and population-based screening, it has been proposed that the definition of hemochromatosis be changed [1, 21, 22]. The difficulties raised by exploring new case definitions in the four hemochromatosis screening programs discussed here are threefold. First, comparisons between program findings and previous research must be made by using reported prevalences based on similar criteria (the presence or absence of iron overload and clinical symptoms). Second, the penetrance of hemochromatosis is not 100%; thus, genetic tests and even biochemical criteria for the early diagnosis of hemochromatosis are new and are not yet fully correlated with clinical outcomes [1, 21]. Third, participating physicians may be unfamiliar with these new criteria; moreover, the existing literature may contradict screening protocols and confuse patient care.
Selection of Screening Threshold Values and False-Positive Cases
When these screening programs were being planned, transferrin saturation threshold values were chosen to establish a screening threshold that would be sensitive enough to identify most cases of hemochromatosis without producing too many false-positive results [18-20]. Recommended threshold values range from 45% to 70% [6-16]. However, the underlying demographic characteristics of the population being screened may influence the transferrin saturation threshold and the prevalence of hemochromatosis [23-26]. For example, a lower cut-point has been suggested for women because it has been shown that at a relatively high transferrin saturation, such as 62% or more, 40% of putative female homozygotes do not screen positive for hemochromatosis even though almost 100% of male homozygotes do [12, 20]. In addition, studies suggest that threshold values should be lower for black persons than for white persons [23, 24]. These lower cut-points have not been directly tested for their association with the newly described genetic HFE mutations or clinical outcomes [27-29].
Because of the low prevalence of hemochromatosis in the population (at most, 8 per 1000 among white persons in the United States), the positive predictive value of the initial random transferrin saturation test for hemochromatosis is also low. In this case, it is only 0.08, with a sensitivity of 0.96 and a specificity of 0.94. In the four screening programs, the transferrin saturation was elevated on initial testing in 2.5% to 5.8% of the several populations screened (Table 2). A repeated test, done while the patient is fasting, with a threshold equal to or higher than that used for the initial test (Table 1) markedly improves the test's positive predictive value [4]. In most patients, hemochromatosis was excluded because the result of the second test was normal. However, 30% of patients who had an elevated transferrin saturation on a repeated test were found to have a primary liver disorder or secondary iron overload. The underlying prevalence of these conditions in a population affects the number of false-positive results for hemochromatosis. In some instances, hemochromatosis coexists and acts synergistically with these other conditions, resulting in a more complicated clinical picture and possibly an altered treatment plan.
Variability and Lack of Standardization of the Transferrin Saturation Screening Test
Serum transferrin saturation is considered a sensitive and specific marker for hemochromatosis [5, 16], but biological and analytic variability complicate its use. The variation may be greater than physicians are accustomed to, and the proper interpretation of such high within-subject variation must be explained. For example, the results of initial and repeated transferrin saturation tests may vary by as much as 50% in the same person (that is, the second value may be 50% lower than the first). Biological (individual) variability requires that the second test be done while the patient is fasting, and the patient has to have taken no vitamins or iron supplements for 24 hours. Even with these dietary restrictions, however, transferrin saturation can still vary considerably in the same person. Each program described here used only a single laboratory to perform transferrin saturation testing; thus, variations were not due to interlaboratory differences. The persistent variation that the Kaiser Permanente program experienced despite standardized blood sampling conditions led them to investigate the cause of the variation. By sending split specimens to an outside laboratory and comparing the results with in-house results, they documented that the variation was due to biological and not analytic causes.
Lack of laboratory standards and proficiency testing for transferrin saturation testing may also cause variability of test results and may affect the proportion of positive results (Table 2). Laboratory proficiency in testing transferrin saturation and its total iron-binding capacity component are not routinely monitored by any national agency. Many methods and instruments are available for measuring transferrin saturation, but which ones are most reliable or valid is not known [30]. Individual physicians can send serum specimens to laboratories that have been evaluated by the College of American Pathologists or the Centers for Disease Control and Prevention and can encourage participating laboratories to be evaluated by these agencies before initiating iron status screening.
Physician Education and Involvement
Early diagnosis and management of hemochromatosis are possible only when physicians are knowledgeable about the techniques involved. Many physicians, however, are not well versed in these areas or in basic genetics [31-33]. Little information is available on newer case definitions of hemochromatosis and the management of young or asymptomatic patients.
In all of the screening programs discussed here, participating primary care physicians were initially unconvinced that hemochromatosis existed in their patient population. Many physicians were unfamiliar with the transferrin saturation test, and this resulted in the ordering of inappropriate tests instead. Resistance to diagnostic algorithms is common, particularly when they differ from protocols learned during medical training.
All of the screening programs reported that a one-time continuing medical education session for participating physicians was inadequate preparation for screening: Physicians require in-depth, ongoing education about hemochromatosis screening and management. To address this need, Kaiser Permanente created videotapes showing clinical manifestations and patient concerns; St. John's Health System mailed educational packets on diagnosis and management to physicians when a patient's initial test result was positive. This mailing was followed by a telephone call or a personal visit from the primary investigator. All programs reported that physician involvement in hemochromatosis screening and in education programs increased as cases were detected.
The screening and diagnostic algorithms for hemochromatosis and the record keeping required to track laboratory and therapeutic phlebotomy are complicated, and it is difficult to standardize patient care among primary care physicians and specialists. To address these problems, the Kaiser Permanente program adopted a centralized approach to hemochromatosis screening and management that relied on two primary care physicians and on selected referral physicians who were familiar with the protocols.
Most physicians wanted assistance not only with the logistics of screening but also with the process of giving information on screening and disease to their patients. In addition, patients reported frustration with the lack of information available to them. To address these needs, programs offered the services of genetic counselors or screening program staff to educate patients about hemochromatosis. The Rochester General Hospital program created a patient information sheet, which was adapted by the St. John's Health System program. The latter program also created numerous other patient education materials. Kaiser Permanente developed videotapes and a book on hemochromatosis [34]. The screening program directors emphasized the value of sharing pretested patient education materials used in existing programs.
Informed Consent and the Implications of Genetic Diagnoses
As a common, treatable genetic disease, hemochromatosis was a valuable test case for the ethical, legal, and social concerns surrounding genetic diagnoses. Most of the human-subject review boards involved challenged the proposed hemochromatosis screening programs because of the lack of policies on informed consent for genetic screening.
Because hemochromatosis is a genetic condition, even genetically diagnosed homozygous patients without iron overload or heterozygous patients can face discrimination in obtaining health or life insurance or employment [35]. Heightened concern about genetic testing must be balanced against the reality that the health consequences of hemochromatosis can largely be prevented with early detection. The patient is poorly served if concerns about medical discrimination supersede concerns about health. As with many other medical conditions, particularly genetic conditions, physicians may have to advocate for patients to insurance companies and employers to prevent or mitigate the consequences of a diagnosis of hemochromatosis.
Screening programs were required to include eight types of information in informed consent documents for hemochromatosis and iron status screening.
1. Background on hemochromatosis and iron deficiency, including the prevalence and natural history of these conditions.
2. The value of iron status screening and diagnostic testing for the patient.
3. The biochemical or genetic tests that may be used to diagnose hemochromatosis and iron deficiency and whether the tests are approved or standardized. Genetic tests, in particular, may be at various stages of approval by the U.S. Food and Drug Administration or may not meet the requirements of the Clinical Laboratory Improvement Act. If a test is not approved, it must be described and defined as a research tool. The patient needs to know whether the tests are valid and reliable (that is, whether the information that the tests provide is similar to that supplied by other tests).
4. Who will have access to the patient's test results, and why. For example, test results may go to project staff, to the patient's primary care physician, to the patient's medical record, or to any combination of these. Patients need to know whether the information will be in their medical records for future insurers to see if they leave the health plan or research program.
5. The protection that the project will give patients who confront social, legal, or insurance consequences of a diagnosis of hemochromatosis. For example, all four of the sites discussed here guaranteed continued full and consistent medical coverage of patients regardless of the results of screening, but this guarantee could be extended only as long as the patients remained in the health plan. As they might with any preexisting medical condition, patients could have faced underwriting problems if they had switched insurers in the future. The St. John's Health System program, in collaboration with the Greene County medical society and the Missouri State health department, sponsored state legislation to prevent genetic discrimination.
6. The tests required to diagnose hemochromatosis and iron overload (such as liver biopsy or quantitative phlebotomy) within the research protocol. It should be stated that separate consent documents will be offered for these procedures if they are indicated. In contrast, if further testing is done at the discretion of the physician on the basis of clinical status, the consent document does not need to name these tests because they are potential rather than defined decisions.
7. Whether serum or blood specimens will be stored for use in future research projects and whether they will be linked to the patient's identity. Separate consent forms should be provided for banking specimens so that participation in a screening program does not depend on a patient's willingness to have specimens stored for future testing.
8. Plans for screening, diagnosis, and treatment of a patient's family members. Patients need to be informed that if they have hemochromatosis, their family members are at risk for the disease. Family member screening often requires separate consent forms because family members are recruited in a different way, may have other health insurance, and may be in other locations. For persons younger than 18 years of age, signed parental consent and the child's signed assent document must be obtained.
Consent forms must be at an appropriate reading level. In large screening programs, one-on-one education about informed consent may be impossible. In these situations, videotapes, group meetings, and written materials explaining aspects of the informed consent documents may be necessary. For example, the St. John's Health System program had nurses use bulleted scripts and slides to present the necessary information. These alternative methods to one-on-one counseling of patients by investigators may save time, but they may also require the training and management of ancillary staff and the creation and field testing of educational materials.
The mechanism for obtaining the patient's consent for hemochromatosis screening depends on whether the screening is considered to be research or part of a routine medical evaluation. The Rochester General Hospital and St. John's Health System programs considered hemochromatosis screening to be research and required written informed consent from each patient, separately, for phenotypic and genetic testing before any testing was done. In the Kaiser Permanente and Veterans Affairs programs, phenotypic testing for hemochromatosis was considered part of the routine medical evaluation. That is, these programs assumed that patients agreeing to receive routine medical care consented to the health services that their physician or health plan considered valuable, including the transferrin saturation test. If a patient had a positive result on an initial screening test, he or she was asked to return for a repeated transferrin saturation test and further evaluation of hemochromatosis or other disorders, as indicated. Evaluation for iron overload and genetic testing was undertaken only in patients who consented to such testing.
Whether justifiably or not, hemochromatosis screening is receiving heightened ethical scrutiny because hemochromatosis is a genetic condition. Furthermore, although both the transferrin saturation test and molecular DNA tests can result in the diagnosis of a heritable disease, institutional review boards consider the gene test to be more sensitive and potentially more damaging. These social issues can be partially managed in the local community or health care system, but federal guidelines and possibly laws forbidding discrimination against persons with genetic disorders will probably be necessary.
Patient Enrollment and Compliance
As noted, in the Kaiser Permanente and Veterans Affairs programs, hemochromatosis screening was considered part of routine health care. Thus, no informed consent was required for the initial transferrin saturation test, and “enrollment” was consequently 100%. In contrast, the Rochester General Hospital and St. John's Health System programs considered hemochromatosis screening to be research and required signed informed consent for patient participation; enrollment at the recruitment sites ranged from 19% to 94% for the Rochester program and 0% to 100% for the St. John's program [18].
Between 80.2% and 98% of patients who were eligible for a repeated transferrin saturation test underwent this test (Table 3). In the St. John's Health System program (the only one to offer genetic testing from the start of the program), 89% of patients opted to have this test. In contrast, when Kaiser Permanente recontacted patients from the original group of patients whose initial screening was positive, only 57.1% consented to genetic testing.
In all screening programs, the major variable influencing the enrollment rate and compliance with follow-up procedures was the level of interest of the primary care physicians. The wide range in enrollment rates at the different program sites seemed to be related to physician interest and to the degree to which screening program staff were actively involved. It was reported that if cases were found at one program site, the motivation for continued screening and enrollment by the staff at that site increased markedly. The high compliance rates for quantitative and maintenance phlebotomy at Kaiser Permanente and St. John's Health System may be due to the interest and enthusiasm of the physicians involved in those programs.
All of the programs made extraordinary efforts to maintain compliance. For example, at Kaiser Permanente and St. John's Health System, the project managers called patients and mailed three or more letters to notify patients of missed or upcoming appointments. Kaiser Permanente staff reported that older men and Hispanic persons were the least compliant with follow-up screening and phlebotomy therapy. St. John's Health System advocated working with the community blood bank to decrease therapeutic phlebotomy charges.
These efforts to increase compliance are unlikely to be sustainable in many health care settings where iron status screening is only part of the overall care provided; thus, compliance rates reported in these settings may be higher than those that would be expected in other settings. Ideally, follow-up would be automated so that the risk for losing track of patients with abnormal test results is minimized. Although rates of compliance with phlebotomy therapy (70% to 84%) may seem low considering the therapy's potential benefits, they compare favorably with rates of compliance with other medical treatments, such as taking medication for hypertension or making dietary changes for obesity [36, 37]. For most patients, these compliance rates reflect less than 1 year of treatment; rates would be expected to decrease over time. Compliance affects every aspect of a screening program; it is therefore important to establish actual compliance rates to calculate the cost-effectiveness of a hemochromatosis screening strategy correctly [38-41].
Incidental Detection of Iron Deficiency
Iron status screening detects far more iron-deficient patients than patients with hemochromatosis, even though the transferrin saturation test is not the test recommended for iron deficiency screening (Table 1) [42]. This is even more true in programs such as the one at St. John's Health System, where the population being screened contains more young women who have a higher risk for iron deficiency because of pregnancy, childbirth, and menstrual blood loss. In the United States, the estimated overall prevalence of iron deficiency varies from 5% to 10% [42, 43]; thus, this condition is 10 to 20 times more common than hemochromatosis. However, these two conditions interact [44, 45], and patients with a genetic risk or an elevated transferrin saturation value can still be iron deficient according to other measures. These patients should be followed over time for the development of iron overload. The high prevalence of iron deficiency means that the screening program must plan what to do with patients with low transferrin saturation (<15%) and must establish how these patients should be evaluated further for the presence and causes of iron deficiency or anemia.
In the Rochester General Hospital program, after the first 300 participants were screened and the high prevalence of low transferrin saturation values became apparent, serum ferritin concentration was routinely assessed in all patients with transferrin saturation values less than 15%; this was done to identify truly iron-deficient patients. This protocol was also adopted by the Veterans Affairs Medical Center program. In contrast, St. John's Health System and Kaiser Permanente evaluated patients for anemia rather than iron deficiency. In the St. John's Health System program, patients with transferrin saturation values less than 15% were advised to have a complete blood count to screen for anemia. Kaiser Permanente conducted anemia screening by using a hematocrit simultaneously with the initial transferrin saturation test, and they evaluated a low hematocrit as indicated.
In adults, iron deficiency without anemia is itself not correlated with poor health outcomes. The full evaluation of iron deficiency based on the transferrin saturation test involved more time, personnel, and financial resources than the programs had planned to use. A cost-effectiveness analysis of evaluation for iron deficiency among patients enrolled in hemochromatosis screening programs may help future programs decide on the best strategy for handling possible cases of iron deficiency.
Program Findings
In the two screening programs that have been completed, the estimated prevalence of iron overload due to hemochromatosis (based on either biopsy or elevated mobilizable iron stores) was 4.2 to 4.5 per 1000 persons (Table 1). Although most of these cases were in white persons, the prevalence of iron overload among Hispanic patients in the one population with large numbers of Hispanic patients was 5 per 1000 persons [25]. These data confirm the prevalence of iron overload from hemochromatosis reported in the recent literature and document the occurrence of hemochromatosis in nonwhite populations [5, 16, 19, 24, 25].
Of the 63 persons found to have iron overload in the Kaiser Permanente program, 36 later consented to genetic testing for the two HFE mutations. Of the 36, 18 were homozygous for C282Y, 5 were homozygous for H63D, 5 were compound heterozygous, 2 were heterozygous for C282Y, 1 was heterozygous for H63D, and 5 did not carry either mutation. To date, DNA results are not available from the other sites.
Conclusions
Despite the different characteristics of the populations screened in these programs, the prevalence of hemochromatosis with iron overload is consistent with the figure of 2 to 5 per 1000 persons reported in the recent literature. The current case definition in the literature, which requires iron overload to be present before hemochromatosis can be diagnosed, should be reconsidered. Transferrin saturation screening allows hemochromatosis to be identified well before iron overload and its complications occur. Thus, we propose that hemochromatosis be defined by the persistent elevation of transferrin saturation measurements with or without genetic tests [21, 22]. In the second stage of evaluation, programs should assess patients for iron overload, starting with serum ferritin levels and proceeding with further workup as indicated. Patients with normal serum ferritin concentrations receive a diagnosis of hemochromatosis without iron overload. If cases of hemochromatosis without iron overload had been included in the prevalence rates in the four programs, the rates of diagnosis of the disease would have almost doubled.
A change in the case definition of hemochromatosis will require a new management algorithm that treats persistently elevated transferrin saturation or selected DNA results (homozygosity for either C282Y or H63D or compound heterozygosity) as major risk factors for the development of iron overload from hemochromatosis. Currently, patients with these characteristics merit observation and biennial follow-up with serum ferritin testing so that iron overload can be detected and treatment can be initiated [21, 46]. Identification of the factors that influence the progression from a genetic predisposition to a clinical problem that requires therapy is a priority for future research.
Because of its availability, low cost, high sensitivity, and acceptable specificity, the transferrin saturation test (administered in two steps) is currently the most appropriate initial screening test for hemochromatosis [47]. The most troublesome aspect of the transferrin saturation test, however, is its low positive predictive value [20], which is due largely to the low prevalence of hemochromatosis and is compounded by biological and analytic variability and uncertainty about laboratory proficiency. The result is that hemochromatosis screening programs will produce numerous false-positive test results that must be differentiated from true cases of hemochromatosis by follow-up testing and careful evaluation [18]. These difficulties are offset by the fact that many patients with false-positive results are, on evaluation, found to have hepatitis, other liver diseases, secondary iron overload, or other diseases that may improve with treatment [18].
Educating physicians about the detection and management of hemochromatosis is critical to the success of iron status screening programs. Patient compliance with screening and management seems to be closely linked to physicians' involvement and enthusiasm for the program. The more aware physicians are of iron abnormalities, the more prepared they are to convincingly advocate for testing and appropriate treatment, the more likely that patients will comply with this preventive health measure, and the more cost-effective the strategy becomes.
The experiences of programs such as those described here will ultimately decide the place of hemochromatosis screening in the health care of adults. Many questions remain to be answered before large-scale hemochromatosis screening will be advocated by national public health agencies [4, 48]. Yet integrating iron status screening into routine medical care for adults has many benefits. In addition to detecting and treating hemochromatosis to prevent chronic diseases among persons who are susceptible to them, screening may also detect other conditions, such as liver diseases, hemolytic anemia, and iron deficiency. This screening may ultimately prove to be appropriate not only for symptomatic patients and patients with an appropriate family history but for all adults.
- Copyright ©2004 by the American College of Physicians
