The role of serum ferritin in the management of idiopathic haemochromatosis

Effectiveness of Erythrocytapheresis in Idiopathic Hemochromatosis. Report of 14 Cases

Thirteen men and one woman (mean age 48.8 yr ± 6.9, range 36–63) with idiopathic hemochromatosis were treated by erythrocytapheresis. Iron depletion followed 9–60 months treatment (median 24), with 21–203 erythrocytaphereses (mean 93 ± 61) and total iron removal of 4.2–40. 6 g (mean 19 ± 11.9). Trasferrin saturation decreased from 90 ± 8.7% to 17 ± 10.6% and serum ferritin from 3164 μg/L ± 1488 to 60.5 μg/L ± 77.5, and liver iron content normalized in all cases. Initial serum ferritin in the patients who were iron-depleted at 18 months (50%, cumulative percentage) was significantly lower than in those still iron loaded at that time (2280 μg/L ± 940 vs 4049 μg/L ± 1444, p<0.02). Clinical improvement was noted in all cases with about a 30% decrease in insulin requirement in most diabetics. Thus erythrocytapheresis appears to be effettive and safe in obtaining iron depletion in idiopathic hemochromatosis.

Improved detection of hereditary haemochromatosis

AIMS

There is high prevalence of hereditary haemochromatosis (HH) in North European populations, yet the diagnosis is often delayed or missed in primary care. Primary care physicians frequently request serum ferritin (SF) estimation but appear uncertain as how to investigate patients with raised SF values. Our aim was to develop a laboratory algorithm with high predictive value for the diagnosis of HH in patients from primary care with raised SF values.

METHODS

Transferrin saturation (Tsat) was measured on SF samples sent from primary care; 1657 male and 2077 female patients age ≥ 30 years with SF ≥ 200 μg/L. HFE genotyping was performed on all 878 male and 867 female patients with Tsat >30%.

RESULTS

This study identified 402 (206 men; 196 women) C282Y carriers and 132 (58 men; 74 women) C282Y homozygotes. Optimal limits for combined SF and Tsat values for HH recognition were established. The detection rate for homozygous C282Y HH for male patients with both SF ≥ 300 μg/L and Tsat >50% was 18.8% (52/272) and 16.3% (68/415) for female patients with both SF ≥ 200 μg/L and Tsat >40%.

CONCLUSIONS

The large number of SF requests received from primary care should be used as a resource to improve the diagnosis of HH in areas of high prevalence.

The laboratory assessment of iron status--an update

The description by Ramsay in 1957 of a practical way of determining the total iron binding capacity of serum (a measure of transferrin concentration) provided a diagnostic test for both iron deficiency and iron overload. Since 1957 the introduction of the assay for serum ferritin (in 1972) has made it possible to assess the levels of storage iron in normal subjects and assays for free erythrocyte protoporphyrin and the circulating transferrin receptor methods to evaluate iron supply for erythropoiesis. In 1957 iron metabolism in man was already well understood but its evaluation relied on measurement of tissue iron concentrations and the use of radioisotopes of iron to measure rates of erythropoiesis. The evaluation can now be carried out using the various blood assays along with the measurement of haemoglobin concentration but interpretation of the measurements in disease still requires an understanding of the way in which these measures are influenced by pathological processes.

Non-invasive assessment of tissue iron overload in the liver by magnetic resonance imaging

We investigated the clinical usefulness of a standard magnetic resonance imaging (MRI) system for non-invasive determination of the liver iron concentration in 38 patients with iron overload and 15 normal controls by measurement of the signal intensity ratio between liver and skeletal muscle (SIR). However, SIR was found dependent on the applied repetition time (TR) of the MRI system, which led us to investigate this relationship in autopsy material of liver and muscle tissue specimens with various iron content. Based on these results, adjustment of SIR measurements to a constant value of TR was achieved. By use of this technique we found a close correlation between MRI and chemically determined liver iron concentration (r2 = 0.98) as well as the serum ferritin concentration (r2 = 0.86). The reproducibility was sufficiently good for the use of MRI in the follow-up of iron reductive treatment. The use of iron store parameters in serum was found insufficient as indicators of endpoint for venesection therapy, if 20 mumol Fe/g dry weight was applied as the upper reference limit of the liver iron concentration. It is concluded that MRI based on SIR measurements offers a precise and reproducible non-invasive method for the determination and follow-up of iron overload within a wide range of liver iron concentrations. Our findings may increase the clinical use of MRI in haematological patients with iron overload.

Magnetic resonance imaging in idiopathic hemochromatosis

The therapeutic management of patients with idiopathic hemochromatosis (IH) requires an accurate estimate of hepatic iron overload in order to prevent tissue fibrosis and organ failure. Magnetic resonance imaging (MRI) was used to estimate liver iron overload in 5 patients with IH and in 8 normal controls. Signal intensity ratio between liver and subcutaneous fat in T1-, proton- and T2-weighted images was significantly lower in IH when compared with normal controls, and increased gradually during treatment by phlebotomy. Mean serum ferritin at diagnosis was 755 micrograms/l (range: 648-900) in IH and 85 micrograms/l (range: 19-232) in normal controls. A high correlation (r = -0.93) was present between liver signal intensity ratio and serum ferritin; both changed in parallel during removal of iron by phlebotomy. MRI may provide a safe and accurate method of detecting iron overload in the precirrhotic phase of IH, obviating the need for liver biopsy. It may also be used to monitor treatment.

Diagnosis and clinical evaluation of iron overload

Diagnostic evaluation of the various forms of iron overload requires information about the total amount and distribution of iron stores. Direct information on the quantity of storage iron can be obtained only by its mobilization in response to repeated phlebotomy or after dilution of a labelled iron test dose in the total body iron pool. Both approaches are cumbersome and time-consuming and are suitable only for research purposes. Detailed information on the amount and distribution of tissue iron in iron overload can be obtained from biopsy specimens of the major iron storage organs such as the liver and bone marrow. However, the invasive nature of these procedures limits their clinical usefulness. Indirect measures, such as serum iron concentration, TIBC saturation, serum ferritin, chelate-induced urinary iron excretion or intestinal iron absorption, and ferrokinetic measurements may provide useful information on the amount of total body iron reserve. However, they all have important limitations in their diagnostic use for evaluating iron overload. The most suitable indirect storage iron index among these methods is the ferritin assay, which has a well established place in the diagnosis of iron overload and monitoring of the effect of therapy. Recent developments in physical methods such as CT, SQUID and NMR have significantly improved the applicability of these techniques for non-invasive measurement of liver iron. It is expected that quantitative measurement of hepatic iron stores will soon be integrated into the diagnostic procedures available by imaging techniques such as CT and NMR. In combination with screening parameters such as serum ferritin and TIBC saturation these new but expensive diagnostic tools may simplify and shorten the diagnostic process and may also be useful for monitoring the treatment of iron overload by phlebotomy or chelating drugs.

Monitoring of intensive phlebotomy therapy in iron overload by serum ferritin assay

Four patients with idiopathic hemochromatosis were treated with intensive phlebotomy therapy. In 1 to 2 years, 8.8-16.7 g iron was removed. In three out of four patients hemoglobin levels fell at the end of therapy. Serum ferritin was continuously measured during therapy. The greatly elevated serum ferritin levels normalized or decreased to subnormal levels in all patients after therapy. Despite some fluctuations in the first phase of therapy, the fall in serum ferritin was regular with halving of the ferritin levels after about 50% of the excess iron was removed. The normalization of serum ferritin occurred in advance of the hemoglobin decrease at the end of therapy, indicating that in the later stages of therapy the normal iron stores are also depleted. It is emphasized that serum ferritin measurements are useful for monitoring of intensive phlebotomy therapy, and in particular to indicate the end of therapy before anemia develops.

Evaluation of liver iron content by computed tomography: its value in the follow-up of treatment in patients with idiopathic hemochromatosis

The therapeutic management of patients with idiopathic hemochromatosis (IH) implies the evaluation of excess hepatic iron. This work was undertaken to confirm the value of computed tomography for the assessment of liver iron overload in such patients and to evaluate this technique during the course of treatment by phlebotomy. The study included 24 patients with initially untreated IH and 7 patients previously treated by phlebotomy for 10 months to 7 years. Follow-up was obtained in 15 subjects. In patients with untreated IH, liver attenuation coefficient (LAC) was always markedly increased (92.4 +/- 7.1 Hounsfield units) as compared with LAC of subjects with normal liver (60.2 +/- 3.1 Hounsfield units) and that of patients with chronic liver disease (53.8 +/- 4.8 Hounsfield units), and was found to be specific for liver iron overload. LAC decreased progressively during phlebotomy, and this diminution was correlated with the amount of mobilized iron (r = 0.79, p less than 0.001); it returned to normal values only after complete removal of iron overload. LAC was closely correlated with liver iron concentration (r = 0.83, p less than 0.001), better than usual biochemical parameters, especially serum ferritin (r = 0.70, p less than 0.01). This study confirms that the determination of LAC on computed tomography provides a reliable index of hepatic iron stores in patients with IH, without requiring a liver biopsy, and shows that this noninvasive method is of particular interest for the follow-up of patients treated by phlebotomy.

Diagnostic workup bias in the evaluation of a test. Serum ferritin and hereditary hemochromatosis

Two studies report markedly divergent results about the usefulness of serum ferritin in diagnosing iron overload in relatives of patients with hereditary hemochromatosis. One study found the sensitivity of elevated serum ferritin to be 0%; another study found a sensitivity of 100%. Although different genetic abnormalities in iron or ferritin metabolism may explain the different results, our examination of these studies suggests that diagnostic workup bias also may explain the difference. In the study reporting a sensitivity of 100%, relatives with normal serum tests may have been excluded from consideration for liver biopsy, thus preventing detection of iron overload. The controversy may provide an empirical illustration of diagnostic workup bias.

Effect of ascorbic acid deficiency on serum ferritin concentration in patients with beta-thalassaemia major and iron overload

The incidence of ascorbic acid (AA) deficiency and its effect on serum ferritin concentration relative to body iron stores was studied in 61 unchelated patients with beta-thalassaemia major. Thirty-nine (64%) of patients had subnormal leucocyte ascorbate concentrations without clinical evidence of scurvy. The lowest leucocyte ascorbate concentrations tended to occur in the most transfused patients. No correlation was found between the units transfused and serum ferritin concentration in the AA-deficient patients but a close correlation (r = +0.82; p less than 0.005) existed for the AA-replete group. Similarly a close correlation (r = +0.77; p less than 0.005) was obtained between liver iron concentration and serum ferritin in AA-replete patients but only a weak correlation (r = +0.385; p less than 0.025) existed for the AA-deficient group. When AA-deficient patients were treated with ascorbic acid, serum iron and percentage saturation of iron binding capacity rose significantly; serum ferritin rose in 13 of 21 patients despite the simultaneous commencement of desferrioxamine therapy. In contrast all three measurements tended to fall in AA-replete patients with ascorbic acid and desferrioxamine therapy. Thus, AA deficiency is commonly present in beta-thalassaemia patients with iron overload and may give rise to inappropriate serum ferritin concentrations in relation to body iron stores.

Computed tomography for determining liver iron content in primary haemochromatosis

Dual-energy computed tomography (CT) was used to estimate hepatic iron concentration in eight patients with primary haemochromatosis with varying degrees of iron overload. The values corresponded closely with these derived from chemical analysis of liver tissue obtained by biopsy (correlation coefficient 0.993). Dual-energy CT therefore seems to provide an accurate and non-invasive alternative to liver biopsy as a means of measuring liver iron concentration in patients with primary haemochromatosis and possibly other iron overload states.