Screening for iron overload using transferrin saturation

Effects of oral or parenteral iron supplementation on haematological parameters, blood iron status and growth in newborn calves fed milk replacer

BACKGROUND

This study aimed to assess the influence of early life iron supplementation on the haematological parameters of calves fed milk replacer on a high plane of nutrition.

METHODS

Thirty calves were allocated to receive either a sham treatment (CON), injection of 1000 mg Fe3+ (INJ) or oral administration of 1050 mg Fe3+ (ORAL), all administered less than 1 hour after birth. Blood was obtained before treatment, on days 1, 3, 5 and 7 of life and once weekly until week 9. Samples were analysed for haemoglobin (Hb), packed cell volume (PCV) and estimated transferrin saturation (%TSAT).

RESULTS

The Hb and PCV of calves in the INJ and ORAL groups were above the values of those in the CON group throughout the study. Hb and PCV of the CON group remained within the reference range for calves. The %TSAT exceeded reported ranges in the ORAL group in the first week. Values for the CON group were below the INJ and ORAL groups throughout the entire study. Average daily gain did not differ between treatments.

LIMITATIONS

The sample size was insufficient to assess the influence of iron supplementation on disease development. Furthermore, the study was set in a controlled environment and not performed under field conditions.

CONCLUSIONS

Oral and subcutaneous iron administration had similar effects on haematological development but resulted in numerically different transferrin saturation. Control animals showed lower Hb and PCV but did not develop overt anaemia.

Effect of Iron Chelation Therapy on Glucose Metabolism in Non-Transfusion-Dependent Thalassaemia

AIMS

To compare insulin sensitivity, β-cell function and iron status biomarkers in non-transfusion-dependent thalassaemia (NTDT) with iron excess during pre- and post-iron chelation.

METHODS

Subjects with NTDT, aged older than 10 years, with serum ferritin >300 ng/ml, were included. Iron chelation with deferasirox (10 mg/kg/day) was prescribed daily for 6 months.

RESULTS

Ten patients with a median age of 17.4 years were enrolled. The comparison between pre- and post-chelation demonstrated significantly lower iron load: median serum ferritin (551.4 vs. 486.2 ng/ml, p = 0.047), median TIBC (211.5 vs. 233.5 µg/dl, p = 0.009) and median non-transferrin binding iron (5.5 vs. 1.4 µM, p = 0.005). All patients had a normal oral glucose tolerance test (OGTT) both pre- and post-chelation. However, fasting plasma glucose was significantly reduced after iron chelation (85.0 vs.79.5 mg/dl, p = 0.047). MRI revealed no significant changes of iron accumulation in the heart and liver after chelation, but there was a significantly lower iron load in the pancreas, assessed by higher T2* at post-chelation compared with pre-chelation (41.9 vs. 36.7 ms, p = 0.047). No adverse events were detected.

CONCLUSIONS

A trend towards improving insulin sensitivity and β-cell function as well as a reduced pancreatic iron load was observed following 6 months of iron chelation (TCTR20160523003).

Liver affection in iron overload studied with serum ferritin and serum aminotransferases

Liver dysfunction as measured by S-ALAT activity was present in 72% of patients over 40 years of age with HLA-related iron overload, mainly detected by laboratory screening. Liver dysfunction was correlated to the amount of iron stored (r = 0.54, p less than 0.001). When iron was removed by phlebotomy, liver function returned to normal. S-ALAT activity was closely correlated to serum ferritin concentration (r = 0.73, p less than 0.001). Even a mild iron excess can affect hepatocytes and result in increased levels of ferritin and aminotransferases in serum. Patients with "transaminitis" should be investigated for iron overload.

Prevalence of hemochromatosis in Finland

Transferrin saturation was determined in 11,431 men and 10,639 women aged 15 or more drawn from different areas in southern and central Finland and attending a multiphasic health screening examination in 1967-1972. All the 163 men and 66 women with transferrin saturation greater than or equal to 70% at the initial examination and still alive at the end of 1983 were invited to a re-examination. Of the invited persons, 76% attended the re-examination. Transferrin saturation and serum ferritin were the initial screening methods in the re-examination. All persons with suspected hemochromatosis were clinically examined and a laparoscopy was performed. Four men and four women were found with unequivocal hemochromatosis. Only one of these cases was diagnosed beforehand. According to these data the prevalence of hemochromatosis in Finland is about 50/100,000.

Alpha-fetoprotein and other tumour-associated antigens for immunotherapy of hepatocellular cancer

BACKGROUND

Hepatocellular carcinoma (HCC) is a leading cause of cancer death, with few treatment options for advanced disease.

OBJECTIVES

Here, we review the aetiology of HCC and focus on recent data on tumour-associated antigens (TAA) for HCC, their functions and potential use as immunological targets for immune-based therapy for HCC. In addition, we examine some aspects of antigen presentation within the liver.

RESULTS/CONCLUSIONS

alpha-Fetoprotein (AFP) has been investigated for many years as a TAA, and has been tested in recent clinical trials. More recently, additional TAA have been identified and new therapeutic approaches have been investigated which may be testable clinically in this difficult disease setting.

Serum and liver iron concentration in dogs with experimentally induced hepatopathy

BACKGROUND AND AIM

Iron (Fe) status is altered in human and experimental animal hepatopathies. In dogs limited data are available. The aim of this study was to investigate serum iron (SI), total iron binding capacity (TIBC), percentage transferrin saturation (SAT) and Fe status in the liver of dogs with experimentally induced hepatopathy.

METHODS

Fourteen 1-year-old dogs were divided into two equal groups. In order for hepatopathy to be induced, 0.25 mL/kg body weight of carbon tetrachloride (CCl4) solution was administered once daily, orally, for a 10-week period in group B dogs, while group A dogs were used as controls. SI, TIBC and SAT values were measured 3 times before the beginning (baseline value) and 10 times at weekly intervals during the experiment. Liver samples, obtained before the administration of CCl4 and at the end of the experimental period (10 weeks), were subjected to Fe determination, as well as to histopathological and histochemical analysis.

RESULTS

At the end of the experiment SI, TIBC and liver iron concentration, as well as liver total iron score were significantly increased in group B dogs. Distribution of granular hemosiderin iron in hepatocytes, Kupffer cells, and portal triads was noticed. Positive correlations were found between SI and liver Fe concentration, as well as histochemically determined Fe. Moreover, positive correlations were evident between liver fibrosis and serum, as well as liver Fe values.

CONCLUSIONS

Experimentally induced chronic hepatopathy in dogs causes Fe status disturbances. Increased serum and liver iron concentration produces liver histopathological deterioration and it may be worth attention during laboratory evaluation in canine hepatopathy.

Frequencies of the hereditary hemochromatosis allele in different populations. Comparison of previous phenotypic methods and novel genotypic methods

AIM

The frequencies of the hereditary hemochromatosis allele were compared for different populations assessed by previous phenotypic methods and the present genotypic methods.

METHODS

From a literature survey, the calculated hemochromatosis allele frequencies from 16 studies using phenotypic biochemical markers (threshold levels for transferrin saturation [range, 46%-70%] and serum ferritin [range, 164-700 microg/L]) were compared with allele frequencies of the Cys282Tyr mutation of the hemochromatosis gene reported in 19 genotypic studies.

RESULTS

Calculated phenotypic allele frequencies are high in Scandinavia: Iceland, 6.1% to 7.4%; Norway, 5.8%; central Sweden, 6.3% to 6.9%; Denmark, 6.1%. Frequencies are similarly high in Wales, Canada, Utah, South Africa, and Australia (range, 5.2%-9.8%). Frequencies are low in Finland (1.9%) and northern Italy (4.5%). Genotypic allele frequencies of the Cys282Tyr mutation are likewise high in Scandinavia. Frequencies are high in the United Kingdom and northern France and low in Finland, central Germany, northern Italy, and Greece. The phenotypic-genotypic ratios of the hemochromatosis homozygosity frequencies for the same geographic area were calculated. A ratio of 1.0 indicates that the 2 methods give similar results. In 3 studies, the ratio was above 1.0, the highest ratio of 1.67 being reported from Italy. In most studies the ratio was slightly below 1.0 (0.71-0.97). The lowest ratio was found in Finland (0.33).

CONCLUSION

In most studies there was good agreement between the hemochromatosis allele frequencies determined by phenotypic and genotypic methods. A high ratio (northern Italy) may indicate that phenotypic selection criteria were too loose and/or that causes of iron overload other than the Cys282Tyr mutation are frequent in the region. A low ratio (in Finland) may indicate phenotypic selection criteria that were too stringent and/or a low penetration rate of the mutation.

Early detection of genetic hemochromatosis: should all young adults be offered the genetic test?

Genetic hemochromatosis (GH) is a late-onset, autosomal recessive disorder. The majority of those at risk from iron overload and its clinical consequences may be detected by a simple genetic test. Furthermore, treatment by phlebotomy, if instituted early, removes excess iron and prevents the complications of iron overload which include arthralgia, diabetes, and cirrhosis of the liver. GH seems to be an obvious candidate for inclusion in national screening programs. However, important questions remain concerning the proportion of individuals with the high-risk genotype who eventually show clinical manifestations of iron overload and the significance of heterozygosity for haemochromatosis in terms of morbidity. Until these questions are resolved, the introduction of widespread genetic screening cannot be justified.

Total iron-binding capacity and serum transferrin determination under the influence of several clinical conditions

In this study TIBC and serum-transferrin concentrations were determined by immunochemical turbidimetry, immunochemical nephelometry and radial immunodiffusion under normal and pathological clinical conditions. A total of 246 (123 male/123 female) patients were included [iron deficiency: 60 (18/42), iron overload: 56 (39/17), chronic inflammation: 47 (23/24), undefined diseases: 35 (16/19), healthy volunteers 48 (27/21)]. The data show that determination of TIBC from conversion of transferrin values using a constant factor results in significantly higher values compared to conversion with a function of first degree. For clinical practice the influence of different diseases is negligible. This study indicates that it is not possible to develop a universal algorithm for the conversion of transferrin values into TIBC.

Population-based screening for hemochromatosis using phenotypic and DNA testing among employees of health maintenance organizations in Springfield, Missouri

BACKGROUND

Hemochromatosis reportedly affects 3 to 8 persons per 1,000 and is associated with an elevated risk of morbidity and mortality. We sought to ascertain its prevalence in a community and to assess the association between phenotype and genotype.

METHODS

All health maintenance organization employees were invited to participate in hemochromatosis screening using a repeated elevation of the transferrin saturation test as the case definition (> or = 50% in women and > or = 60% in men with no other cause). Iron overload from hemochromatosis was defined as serum ferritin concentration > or = 95th percentile and mobilizable iron > or = 99th percentile for age and sex, or hepatic iron index > or = 1.9. The HFE gene was analyzed for mutations.

RESULTS

Participation among employees was 28% (1,653 of 6,000); 83% were women. The prevalence of hemochromatosis was 8 per 1,000 (13 of 1,653), and the prevalence of iron overload from hemochromatosis was 4 per 1,000 (5 of 1,653). Compared with those who had no HFE mutation, the relative risk (RR) for hemochromatosis was greatest for C282Y homozygotes (RR = 147), compound heterozygotes (RR = 19), and H63D homozygotes (RR = 9). Overall, 38% of participants had at least one HFE mutation. Screening based on an initial elevated transferrin saturation test had the best sensitivity, whereas DNA testing offered the best specificity and predictive value positive for iron overload disease.

CONCLUSIONS

In this population, we found a greater than expected prevalence of hemochromatosis and demonstrated a clear association with the HFE genotype. Promotion of screening is complicated by controversies in case definition and the large number of persons who will be detected before they have clinically significant iron loading, in whom the risk of clinical disease is unknown. Larger screening studies in more diverse populations are necessary to characterize the burden of disease and to follow those at risk (based on HFE or iron status measures) to establish the natural history of hemochromatosis.

HFE codon 63/282 (H63D/C282Y) dimorphism in German patients with genetic hemochromatosis

Genetic hemochromatosis (GH) is closely associated with genes of the major histocompatibility complex (MHC) on chromosome 6. Recently, a candidate gene for GH, with structural similarities to MHC class I genes, designated HLA-H and presently named HFE, has been cloned. The HFE gene is localized telomeric to the MHC and several reports have indicated that the HFE gene is mutated in GH patients. In the present study we have analyzed the relationship of HFE gene variants and disease manifestation in GH patients and family members. Fifty-seven patients with GH, 73 family members and 153 healthy blood donors were studied for the amino acid dimorphism at codon 63 (His63Asp=H63D) and codon 282 (Cys282Tyr= C282Y) of the HFE gene. The codon 63 and 282 dimorphism were defined by PCR amplification of genomic DNA samples and restriction enzyme digestion using RsaI/SnaBI for C282Y and BclI/MboI for H63D. Ferritin, transferrin serum levels and total iron-binding capacity were determined prior to therapeutic intervention. The Tyr-282 substitution occurred in 53 (93%) of patients compared with 8 (5.2%) of controls (OR=169, P<0.0001). Fifty-one (90%) patients were Tyr-282 homozygous. In contrast, the Asp-63 substitution was present in 5 (8.8%) of the patients compared with 34 (22%) of controls (OR=0.39, P=NS) with none of the patients being homozygous. In Tyr-282 homozygous GH patients serum ferritin levels, transferrin saturation, liver iron and liver iron index were elevated significantly compared to Tyr-282-negative patients, whereas no difference was observed between Tyr/Cys-282 heterozygous and Tyr-282-negative patients.

HFE mutations in patients with hereditary haemochromatosis in Sweden

OBJECTIVE

To determine the frequency of mutations (C282Y and H63D) in a newly identified gene HFE in patients with hereditary haemochromatosis (HH) in Sweden.

DESIGN

Molecular genetic analyses of the HFE gene (polymerase chain reaction (PCR) followed by enzyme restriction) were performed in genomic DNA from unrelated patients with a clinical diagnosis of HH and in healthy subjects.

SETTINGS

Patients with HH treated with phlebotomies at Karolinska Hospital and Huddinge Hospital were analyzed.

SUBJECTS

Eighty-seven unrelated patients with HH and 117 healthy controls.

RESULTS

It was found that the HFE C282Y mutation occurs in 94.2% of chromosomes from patients with HH. Eighty patients (92.0%) were homozygous for the C282Y mutation and one was heterozygous. Three patients were heterozygous for both C282Y and H63D mutations. One patient was homozygous and one was heterozygous for the H63D mutation. One patient carried normal alleles. In healthy controls, the C282Y mutation occurred in nine subjects (7.7%), all of which were heterozygous. The H63D mutation was found in 28 control subjects, one of which was homozygous.

CONCLUSIONS

We found that the majority of patients with HH have the C282Y mutation in the HFE gene. The frequency of the H63D mutation was higher in controls than in patients with HH, although in chromosomes at risk the frequency of the H63D mutation was higher in patients.

Prevalence of hemochromatosis among first-time and repeat blood donors in Norway

BACKGROUND/AIMS

The observed prevalence of hemochromatosis has ranged considerably from 0.05 to 0.37% in studies requiring liver biopsy. We aimed to study the prevalence of genetic hemochromatosis among Norwegian blood donors.

METHODS

We studied 10,552 healthy blood donors (5312 women and 5240 men) using serum ferritin as a screening parameter. If serum ferritin concentration was > or = 100 micrograms/l in women and > or = 200 micrograms/l in men, serum iron and transferrin (measured as total iron binding capacity = TIBC) were measured. Blood donors who repeatedly had a transferrin saturation above 40% and a ferritin concentration above these limits were referred to a hepatologist (H.B.).

RESULTS

Serum ferritin was > or = 100 micrograms/l in 94/5312 (1.8%) women and > or = 200 microliters in 79/5240 (1.5%) men. Of these, 37 persons had a serum ferritin concentration above 100 micrograms/l (females) or above 200 micrograms/l (males) and a transferrin saturation above 40%. Nineteen of them (13 men and 6 women, median age 36 years, range 28-68) were identified as having hemochromatosis on the basis of increased hepatic iron index. Serum ferritin ranged from 111 to 1980 micrograms/l (median 357 micrograms/l and transferrin saturation from 50 to 100% (median 92%), hepatic iron from 48 to 471 mumol/g dry weight (median 118 mumol/g) and hepatic iron index from 1.5 to 12.1 (median 3.0). One person had cirrhosis and none had diabetes. The prevalence of hemochromatosis was significantly higher among first-time blood donors (12 out of 3500 [3.4/1000]) compared with repeat donors (7 out of 7052 [1/1000]), p < 0.005.

CONCLUSIONS

The observed prevalence of hemochromatosis in Norwegian first-time blood donors of 0.34% is comparable to recently observed prevalences in other studies. However, the use of serum ferritin as a first-step screening tool may have failed to detect hemochromatosis in the early stage where iron overload has not yet occurred.

Practice guideline development task force of the College of American Pathologists. Hereditary hemochromatosis

Hereditary hemochromatosis is an autosomal recessive disorder, the gene for which occurs in approximately 10% of Americans, most of whom are unaffected heterozygotes. Approximately 5/1000 white Americans are homozygous and at risk of developing severe and potentially lethal hemochromatosis. The disorder affects numerous organ systems, but the most common symptoms are fatigue, palpitations, joint pains, and impotence; the most common signs are those that relate to hypothalamic, cardiac, hepatic or pancreatic dysfunction, including poor cold tolerance, impotence in males, amenorrhea in females, cardiac arrhythmias, dyspnea, edema, hepatosplenomegaly, spider telangiectases, ascites, deformity, swelling or limitation of motion of joints, weight loss, hyperpigmentation. Characteristic abnormalities of laboratory tests include elevated serum iron concentration, high transferrin saturation, elevated serum ferritin concentration, elevated serum transaminases, hyperglycemia and low values for thyroid-stimulating hormone (TSH) and gonadotropins. Death may be the result of cardiac arrhythmia, congestive heart failure, liver failure or liver cancer. Since many of these complications cannot be reversed once they have developed, early diagnosis and treatment are essential. In view of the high prevalence in the American population (prevalence varies with ethnic background), the low cost of diagnosis and treatment, the efficacy of treatment if begun early, and, on the other hand, high costs and low success rate of late diagnosis and treatment, systematic screening for hemochromatosis is warranted for all persons over the age of 20 years. The initial screening should be by measurement of serum iron concentration and transferrin saturation. The practice guideline provides a diagnostic algorithm for cases in which the serum transferrin saturation is 60% or greater. It also provides guidelines for clinical management.

Population screening for haemochromatosis: a unifying analysis of published intervention trials

OBJECTIVES

To examine the efficacy of population screening for haemochromatosis by analysing the screening performance of seven intervention trials, and to compare this with the expected performance derived from family studies.

SETTING

Seven population intervention trials carried out between 1983 and 1995 in Australia, Scandinavia, Iceland, and the United State.

METHODS

Seven of 23 English language trials identified were suitable for the meta-analysis. Transferrin saturation and serum ferritin measurements derived from family studies were used to predict detection and false positive rates for each trial.

RESULTS

The seven trials used various screening and diagnostic criteria. A total of 18,396 men and 12,254 women were screened. Because some cases were not detected by screening, and some screen positive individuals did not complete diagnostic testing, the prevalence of homozygous individuals was underestimated in all the trials. The reported and predicted percentages of screen positive individuals nearly always agreed. The homozygote prevalence was estimated to be 34 men and 40 women per 10,000 (prevalence predicted from family studies is 53 per 10,000). Clinical manifestations were present in 50% of male and 44% of female homozygotes.

CONCLUSIONS

False positive rates, homozygote prevalences, and frequency of clinical manifestations were in general agreement with predictions from family studies. However, incomplete understanding about a number of issues requires that further pilot trials be carried out before screening can be considered part of routine medical practice.

Results of surveys to assess iron status in Europe

Many studies have been undertaken to assess the iron status of Europeans. However, differences in dietary patterns, methodology, contraceptive choice, and epidemiologic factors lead to confounding factors that need consideration as the data from available studies are reviewed.

Screening blood donors for hereditary hemochromatosis: decision analysis model based on a 30-year database

BACKGROUND & AIMS

The high prevalence, morbidity, premature death, and benefit of early diagnosis and treatment make hemochromatosis a prime target for screening in the white population. Decision analysis techniques were used to compare the outcome, utility, and incremental cost savings of a plan to screen voluntary blood donors for hemochromatosis.

METHODS

The screening strategy includes sequential testing of serum unsaturated iron-binding capacity, serum transferrin saturation, serum ferritin, and either hepatic iron index or venesections to measure exchangeable body iron. Estimates of prevalence, asymptomatic intervals, probabilities of life-threatening clinical complications, symptom-specific life expectancy, and sensitivity and specificity of screening tests are based on our database of 170 hemochromatosis homozygotes and the published literature.

RESULTS

The screening strategy led to an incremental increase in utility of 0.84 quality-adjusted life days with an incremental cost savings of $3.19 per blood donor screened. When the potential of identifying asymptomatic homozygous siblings was included, these values increased to 1.18 quality-adjusted life days and $12.57 per person screened. Screening remained a dominant strategy given a prevalence of hemochromatosis of > 0.0026 or an initial screening test cost of < $8.

CONCLUSIONS

Screening blood donors for hemochromatosis has the potential to improve overall societal health status and decrease third-party payer health care costs over the long-term.

Iron deficiency and iron overload in Swedish male adolescents

OBJECTIVES

The present study was undertaken to confirm or reject recent findings indicating a high prevalence of iron deficiency in Swedish male adolescents; a second aim was to study the prevalence of genetic iron overload.

DESIGN

The diagnostic criteria were: anaemia: Hb < 130 g L-1 (a): iron deficiency: serum ferritin (SF) < 12 micrograms L-1 + transferrin saturation (TS) < 16% (b): iron deficiency anaemia a + b. Iron overload: SF (90th percentile) + TS (90th percentile) in repeat tests.

SETTING

Central Sweden.

SUBJECTS

A total 3975 men aged 18 years studied on enrollment into military service.

RESULTS

Serum ferritin averaged 36.8 micrograms L-1. Anaemia was present in 0.5%, iron deficiency anaemia in 0.17% and iron deficiency in 0.4%. If iron deficiency is defined as SF < 16 micrograms L-1, as was recently suggested, the prevalence would be 2.8%. Such a cut-off value would include 73% normal people (false positives). Iron overload had the same prevalence as iron deficiency, 0.4%.

CONCLUSIONS

Iron stores, as measured by serum ferritin, are small in young men studied at the end of their growth spurt. However, iron deficiency is rare. Therefore, the present study has not been able to confirm the high prevalence of iron deficiency recently reported. A prevalence of genetic haemochromatosis of 0.4%, confirms earlier findings and would mean that 12.6% of the population are heterozygotic carriers of the iron-loading genes. These findings give no support for a proposed, more effective iron-enrichment of food. It is not needed and can be harmful.

Clinical spectrum and management of haemochromatosis

Haemochromatosis is one of the most common inborn errors of metabolism. In prospective epidemiological studies the frequency of haemochromatosis is 0.0037 (76/20333 subjects) for homozygotes which corresponds to a gene frequency of 0.061 and a frequency of heterozygotes of 0.115. Abnormality in liver function tests, weakness and lethargy, skin hyperpigmentation, diabetes mellitus, arthralgia, impotence and ECG abnormalities are the most frequent findings and symptoms at diagnosis. In recent years about 50% of patients were detected without having liver cirrhosis and 20% of patients did not have any symptoms and pathology except iron overload. Survival analyses in long-term studies showed that in the absence of cirrhosis and diabetes, iron removal by phlebotomy therapy prevents further tissue damage and guarantees a normal life expectancy. Patients with massive and long-lasting iron overload had a worse prognosis than those with less severe iron excess. Iron removal in general ameliorated liver disease, weakness and cardiac abnormalities, and also prevented the progression of endocrine alterations. Therapy, however, did not influence insulin-dependent diabetes. Most deaths in patients with hereditary haemochromatosis were caused by liver cancers which often occurred many years after complete iron removal. In patients with haemochromatosis, liver cirrhosis, cardiomyopathy, and diabetes mellitus are also significantly more frequent causes of deaths when compared with the general population. Further strategies have to evaluate the design of screening programmes in order to diagnose more patients in the precirrhotic and asymptomatic stage.

Genetics of haemochromatosis

This review is largely concerned with the frequency of genetic haemochromatosis (GH) and attempts to find the gene responsible. Studies of disease prevalence are reviewed along with the association of GH with other inherited disorders. The high prevalence of the disorder found in a number of surveys of populations of European origin along with the relatively few patients presenting with the clinical features of the advanced disease remains a paradox. The tight linkage between HLA-A and GH has been known since 1975 but it has not been possible to distinguish between a telomeric or centromeric location for the gene (HFE) relative to HLA-A. The recent explosion in detailed knowledge of the genetic map of the region telomeric of HLA-A on chromosome 6p has made it possible to examine new genetic markers. The very strong association between GH and D6S105-8 suggests a gene location telomeric to HLA-A. The lack of a precise location, and uncertainty about either the primary biochemical abnormality or the tissues involved has delayed the identification of the gene but expressed genes in the region around HLA-A are now being isolated and tested.

Screening for hemochromatosis: a cost-effectiveness study based on 12,258 patients

BACKGROUND/AIMS

Current emphasis in hemochromatosis has focused on early detection and treatment to prevent permanent liver damage and hepatocellular carcinoma. Thus far, only normal population and high-risk groups have been screened but not patients seeking medical care.

METHODS

Serum iron levels were determined in consecutive fasting blood samples collected in the morning from 12,258 Mayo Clinic patients.

RESULTS

One hundred twenty-seven patients had an initial serum iron concentration > or = 180 micrograms/dL. Eight patients (age, 38-71 years; 7 men and 1 woman) had transferrin saturation > or = 62% (range, 84-99) and serum ferritin value > or = 400 micrograms/L (range, 457-4004) with no other explanation for the abnormal iron test results. Three patients (2 male and 1 female) had markedly elevated hepatic iron concentration (range, 11,080-29,719 micrograms/g dry wt) and hepatic iron index (range, 2.9-8.4) indicative of homozygous hemochromatosis. One patient who refused liver biopsy had 7 g of iron removed by phlebotomy and is likely homozygous. Two patients had hepatic iron indices < 1.5 and are probably heterozygous. The genetic status of 1 patient is indeterminate, and 1 patient with normal hepatic iron concentration and hepatic iron index had chronic active hepatitis. None had cirrhosis, diabetes, or cardiomyopathy. No patients with hemochromatosis would have been detected without this study.

CONCLUSIONS

The yield in this study, 0.33 cases of 1000 screened, is approximately one tenth of the predicted homozygote frequency by recent estimates. Even at this yield, screening appears cost-effective.

Preventing manifestations of hereditary haemochromatosis through population based screening

OBJECTIVE

To evaluate the efficacy of identifying presymptomatic hereditary haemochromatosis through population based screening.

DESIGN

Review the hereditary pattern, prevalence, and clinical manifestations of haemochromatosis. Estimate the detection and false positive rates associated with available screening and diagnostic tests. Develop examples of screening protocols and other components that would be necessary for proper implementation. Identify potential barriers and objections.

CONCLUSIONS

Hereditary haemochromatosis, an autosomal recessive disorder with a prevalence of three to five per thousand in the general population, is associated with a wide variety of clinical manifestations, usually beginning in mid to late adult years. Identifying and treating this disorder after symptoms appear can arrest its progress but usually cannot reverse existing damage to joints, liver, pancreas, pituitary gland, and other organs. Measuring transferrin saturation in serum is now known to be a reliable screening test for haemochromatosis when applied to a general population of healthy adults, detecting about 80% of cases, with a 0.3% false positive rate. Liver biopsy with iron staining and total iron concentration is the recommended diagnostic test for subjects with positive screening tests. Treatment with phlebotomy can then prevent manifestations. Effective systematic identification and management of presymptomatic haemochromatosis in the general population is best accomplished within the framework of an organised screening programme. Potential barriers include accessibility of young adult populations and attitudes in the health community that severe clinical manifestations are relatively uncommon. It is recommended that pilot programmes be undertaken to determine the feasibility of introducing screening for haemochromatosis as part of routine health care.

Screening for haemochromatosis: prevalence among Danish blood donors

Hereditary haemochromatosis is an autosomal recessive disease that is genetically expressed by excessive accumulation of iron in the tissues, resulting in cirrhosis, diabetes mellitus, cardiomyopathy and hypogonadism. As the disease may be diagnosed before the appearance of symptoms, and prevented by repeated phlebotomies, there are strong implications for adoption of a screening procedure. Determinations of transferrin saturation (TS) and serum ferritin concentration (SF) were used to screen 4302 blood donors, who were selected for follow-up studies if they fulfilled any of the following three criteria: (i) TS greater than or equal to 0.7; (ii) TS greater than or equal to 0.5 together with SF greater than or equal to 150 micrograms l-1; (iii) SF greater than or equal to 300 micrograms l-1. A total of 58 subjects who fulfilled at least one of these criteria were reinvestigated, after which 18 individuals still fulfilled at least one criterion. Fifteen subjects having SF greater than or equal to 300 micrograms l-1 were offered liver biopsy and thirteen of these accepted. In one individual, no stainable iron was detected, and two subjects did not fulfil the previously established diagnostic criteria for the diagnosis of hereditary haemochromatosis. Ten subjects who had a high TS and liver iron grade 2-4 according to Bassett were classified accordingly as homozygotes. On the basis of these results, the prevalence of haemochromatosis in Denmark was estimated to be 0.0037-0.0046.

Phenotypic expression of the HLA linked iron-loading gene in males over the age of 40 years: a population study using serial serum ferritin estimations

The frequency of the HLA linked iron-loading gene was assessed in 1783 Afrikaner men over the age of 40 years living in the South Western Cape. Measurements, made on three occasions over a 4.5 year period, included the serum ferritin concentration, a screening test for reduced unsaturated iron-binding capacity and the percentage transferrin saturation. The serum gamma-glutamyl transferase concentration was used as a marker of alcohol abuse. The diagnosis of homozygosity was based on a serum ferritin concentration that was persistently greater than 400 micrograms l-1 and a percentage transferrin saturation greater than 55%. Using these criteria, 17 subjects were diagnosed as homozygous, corresponding to a disease frequency of 0.0095, a gene frequency of 0.0976 and a heterozygote frequency of 0.176 (95% confidence limits: 0.135-0.213). None of the subjects had overt clinical haemochromatosis. Typing for the HLA-A, -B, -C and -DR loci showed that the HLA-A3 allele (frequency 0.6471 and relative risk 4.4) was the only independent marker for the iron-loading gene in this asymptomatic population. Using the present approach it was not possible to distinguish between heterozygotes, alcohol abusers and normal subjects with serum ferritin concentrations at the upper end of the normal range.

Prevalence of haemochromatosis amongst asymptomatic Australians

We determined the prevalence of iron overload due to homozygous haemochromatosis in an asymptomatic Australian (predominantly Caucasian) population by surveying 1968 employees of two large corporations. Subjects were screened by measurement of transferrin saturation and serum ferritin concentration and, in all subjects with elevation of both indices, percutaneous liver biopsy was performed to establish whether significant iron overload was present. The prevalence of iron overload due to haemochromatosis in this population was 0.36%. The prevalence rate was not significantly different between males and females, suggesting that this autosomal recessive disease is expressed equally in females given an adequate dietary iron supply. The positive predictive value of a transferrin saturation consistently greater than 45% together with an elevated serum ferritin concentration was 64%. It is concluded that the prevalence of significant iron overload due to homozygous haemochromatosis warranting treatment is approximately 1:300 and that transferrin saturation should be included in existing adult health screening programmes.

Prevalence of hereditary haemochromatosis in two Swedish urban areas

The prevalence of hereditary haemochromatosis (HH) was studied in Stockholm and Göteborg, the two largest cities in Sweden, using screening with transferrin saturation in combination with serum ferritin and further clinical and laboratory examinations. In Göteborg, none of 1660 men aged 50 and 51 years, randomly selected from the census register, was found to have HH. In Stockholm, nine out of 11,920 male hospital inpatients were diagnosed as having HH. The calculated mean and 95% confidence ranges were consistent with earlier findings in two studies on men in Malmö, the third largest urban area in Sweden. Pooling results from these three main urban areas, the mean prevalence was 0.073% (17/23, 355), which is considerably lower than figures reported from one area in northern Sweden and from pedigree analyses in several other areas in the world. Screening of the US population in the N-HANES II study also showed much lower figures. The reasons for these discrepancies are discussed and it is suggested that the average prevalence of HH in Caucasian populations is probably around 0.1%.

HLA class I and H ferritin gene polymorphisms in normal subjects and patients with haemochromatosis

The gene for idiopathic haemochromatosis is located on the short arm of chromosome 6 within 1 cM of the HLA-A locus. In this region there are many HLA class I genes, and there may also be a gene for the 'H' subunit of ferritin. Both HLA class I and H ferritin genes are therefore candidates for the abnormal gene in idiopathic haemochromatosis. In 15 unrelated patients the frequency of HLA-A3 was 80% compared with 24% for 600 unrelated individuals from South Wales. The most common haplotype involved is probably HLA-A3, B7. DNA was prepared from leucocytes from 12 of these patients and from 85 normal subjects. After digestion with Taq1, electrophoresis, and Southern blotting, class I sequences were detected by hybridisation to an HLA class I probe (pHLA-A). Of the 34 restriction fragments detected, 22 were polymorphic. Particular fragments correlated with the presence of HLA-A antigens A1, 2, 3, 10, 11, w19, and 28, but there was little correlation with B antigens. Restriction fragment patterns specific for haemochromatosis were not found with TaqI or during less extensive studies with other restriction enzymes. No differences in restriction fragment patterns were found between four patients and four normal subjects apparently homozygous for HLA-A3 and B7. Examination of Southern blotting patterns for genomic DNA from patients and normal subjects with a panel of 12 restriction enzymes and a probe for the H ferritin gene (pDBR-2) revealed no polymorphisms associated with either idiopathic haemochromatosis or particular HLA phenotypes. These studies provide no support for either HLA class I genes or the H ferritin gene as candidates for the haemochromatosis gene.

The effect of iron fortification of the diet on clinical iron overload in the general population

The gene coding for idiopathic hemochromatosis is prevalent in Sweden, the country with the highest iron fortification of food (42%) in the world. We wanted to study if this highly iron-fortified diet had negative effects on the iron situation in carriers of the iron-loading genes. Iron stores averaged 6.7 grams in male homozygotes who were mainly identified through laboratory screening. It was 3.4 grams in female homozygotes. By HLA typing of family members of these homozygous probands, 39 additional homozygotes and 172 heterozygotes were detected. Serum ferritin averaged 620 micrograms/l in 20 male and 168 micrograms/l in 19 female homozygotes in the family screening. Storage iron as measured by serum ferritin concentration was slightly but significantly higher in male heterozygotes than controls (117 micrograms/l versus 87 micrograms/l, p less than 0.02). There was no further increase in serum ferritin concentration with age after 40 years. Heterozygotes showed no clinical signs of iron damage. These findings do not indicate that carriers of the iron-loading genes in Sweden have been adversely affected by the highly iron-fortified diet of the country.

HLA as a marker of the hemochromatosis gene in Sweden

The frequency of HLA-A3 and HLA-B14 antigens was found to be significantly (P = less than 0.0001) higher in a series of 50 unrelated and unselected Swedish patients with idiopathic hemochromatosis (IH) than in controls, being 66% and 32% for A3 and 22% and 2% for B14. The haplotype A3B14 was associated with the highest risk in this material (relative risk 23.4). One family with this haplotype was traced back to the end of the seventeenth century. The pattern of HLA antigens associated with IH in Sweden shows remarkable similarity to those reported from England and Brittany.