Transcript Diagnosis of Iron Stores

Diagnosis of Iron Overload
M. Domenica Cappellini, MD
Professor of Internal Medicine
University of Milan
Maggiore Hospital
Milan, Italy
Iron Overload and Disease States
Causes of Iron Overload
• Primary (hereditary)
– Resulting from a primary defect in the regulation of
iron balance, eg, hereditary haemochromatosis
• Secondary (acquired)
– Caused by another condition or by its treatment
 Anaemias requiring repeated blood transfusion
 (eg, thalassaemia, sickle cell disease, and myelodysplastic
syndromes)
 Ineffective erythropoiesis
 Toxic ingestion
Feder JN, et al. Nat Genet. 1996;13:399.
Porter JB. Br J Haematol. 2001;115:239.
Conditions at Risk of Iron Overload
Sources of Iron
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Absorption
+++
+
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++
Haemochromatosis
Thalassaemia major
Thalassaemia intermedia
Sideroblastic anaemia
CDA
Aplasias
Chronic haemolytic anaemias
Myelodysplasias
Off-therapy leukaemias
Bone marrow transplant
Liver disease
+
Porphyria cutanea tarda
+
Neonatal iron overload
Atransferrinaemia
Aceruloplasminaemia
Dietary iron overload
++
Iatrogenic iron overload
Dialysis patients
Courtesy of A. Piga.
Transfusion
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+
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++
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+
++
+
+
Redistribution
+
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Complications of Iron Overload
Iron overload
Capacity of serum transferrin
to bind iron is exceeded
Non–transferrin-bound iron
circulates in the plasma
Excess iron promotes
the generation of free
hydroxyl radicals,
propagators of oxygenrelated tissue damage
Cardiac
failure
Liver cirrhosis/
fibrosis/cancer
Courtesy of Dr. M. D. Cappellini.
Insoluble iron complexes
are deposited in body
tissues and end-organ
toxicity occurs
Diabetes
mellitus
Infertility
Growth
failure
Consequences of Iron-Mediated Toxicity
During Iron Overload
Increased LPI or “free” iron
Hydroxyl radical generation
Lipid peroxidation
Organelle damage
TGF-β 1
Lysosomal fragility
Collagen synthesis
Enzyme leakage
Cell death
Fibrosis
LPI = labile plasma iron; TGF = transforming growth factor.
Cohen AR & Porter JB. In: Steinberg MH, et al, eds. Cambridge University Press;2001:979–1027.
Organ Systems Susceptible
to Iron Overload
Clinical sequelae of iron overload
Pituitary → impaired growth
Heart
→ cardiomyopathy,
cardiac failure
Liver
→ hepatic cirrhosis
Pancreas→ diabetes mellitus
Gonads → hypogonadism,
infertility
Courtesy of Dr. M. D. Cappellini.
Thalassaemia major:
transfusion without
chelation
15
50
Homozygous
haemochromatosis
40
Heterozygote
10
30
Threshold for cardiac
disease and early death
5
20
Increased risk of complications
10
Optimal level in chelated patients
Normal
0
0
10
20
30
Age (years)
Olivieri N, Brittenham G. Blood. 1997;89:739.
40
0
50
Hepatic iron, mg/g of liver, dry weight
Liver Iron (mg/g of liver, wet weight)
Liver Iron and Risk from Iron Overload
Assessing Iron Overload
Diagnosis of Iron Overload
• Established
– % transferrin saturation
– Ferritin
– Liver iron concentration (biopsy)
• Investigational
– Biomagnetic liver susceptometry (SQUID)
– Magnetic resonance imaging
SQUID = superconducting quantum interference device.
Transferrin Saturation
• Normal values: 16%–30%
• > 40%: iron overload
Monitoring—Plasma Ferritin
• Relatively noninvasive
• Routine laboratory assay
• Values confounded by
–
Inflammation
–
Liver function
–
Ascorbate status
Plasma Ferritin (µg/L)
• Inexpensive
24,000
Sickle cell anaemia (n = 37)
Thalassaemia major (n = 74)
12,000
8000
4000
0
0
Brittenham G, et al. Am J Hematol. 1993;42:81.
4000
8000
12000
Hepatic Iron
(µg Fe/g liver)
Serum Ferritin and Risk from
Iron Loading
• Change in serum ferritin over time
reflects change in liver iron
concentration
– Sequential evaluation of ferritin provides
good index of chelation history1
• Maintenance of serum ferritin
<2500 µg/L significantly correlates with
cardiac disease-free survival2-5
1. Gabutti V and Piga A. Acta Haematol. 1996;95:26. 2. Olivieri NF, et al. N Engl J Med. 1994;331:574.
3. Telfer PT, et al. Br J Haematol. 2000;110:971. 4. Davis BA, et al. Blood. 2004;104:263.
5. Borgna-Pignatti, et al. Haematologica. 2004;89:1187.
Measuring and Interpreting
Serum Ferritin
Advantages
Disadvantages
• Easy to assess
• Inexpensive
• Repeat measures are
useful for monitoring
chelation therapy
• Positive correlation with
morbidity and mortality
• Indirect measurement of iron
burden
• Fluctuates in response to
inflammation, abnormal liver
function, metabolic deficiencies
• Serial measurement required
Monitoring—Why LIC?
•
•
Liver iron concentration (LIC) predicts total body storage iron1
Absence of pathology
–
•
Liver pathology
–
–
•
Heterozygotes of hereditary haemochromatosis where liver
levels <7 mg/g dry weight
Abnormal ALT if LIC >17 mg/g dry weight2
Liver fibrosis progression if LIC >16 mg/g dry weight3
Cardiac pathology at high levels
–
Liver iron >15 mg/g dry weight association with cardiac death

–
All of 15/53 thalassaemia major patients who died4
Improvement of left ventricular ejection fraction with venesection
post bone marrow transplantation5
1. Angelucci E, et al. N Engl J Med. 2000;343:327. 2. Jensen P, et al. Blood. 2003;101:4632.
3. Angelucci E, et al. Blood. 2002;100:17. 4. Porter JB. Hematol/Oncol Clinics. 2005;S7.
5. Mariotti E, et al. Br J Haematol. 1998;103:916.
Total Body Iron Stores (mg/kg)
LIC Accurately Reflects Total Body
Iron Stores
300
r = 0.98
0.98
r2 r==0.98
250
200
150
25 patients
with iron overload
and cirrhosis
100
≥1 mg dry weight
liver sample
50
0
5
10
15
LIC (mg/g, dry weight)
LIC = liver iron concentration.
Angelucci E, et al. N Engl J Med. 2000;343:327.
20
25
LIC and Prognosis
Approximate LIC, mg/g dry weight liver
Haemochromatosis
β-thalassaemia
Homozygous
Major
Age
(years)
Normal
Heterozygous
5
10
<1.2
<1.2
<1.2
<1.2
>3.2
~7
>15
>15
15
20
25
30
35
<1.2
<1.2
<1.2
<1.2
<1.2
<1.2
~1.2
>1.2
~3.2
>3.2
>7
~15
>15
>15
>15
>15
>15
(Not surviving)
3.2–7 (adequate iron chelation)
7–15 (increased risk of complications)
15 (cardiac disease and early death)
LIC changes are presented for patients without phlebotomy or iron chelation therapy.
LIC = liver iron concentration.
Courtesy of Dr. J. Porter.
Estimation of LIC
Liver biopsy
• Distribution artifact
• Debate about safe levels
• Safety
• Patient acceptance
• Sample size
– ≥1 mg dry weight
– >4 mg wet weight
Photos courtesy of Dr. J. Porter.
Porter JP. Br J Haematol. 2001;115:239.
2 cm
Measuring LIC by Liver Biopsy
Advantages
Disadvantages
• Direct measurement of LIC
• Validated reference
standard
• Quantitative, specific, and
sensitive
• Allows for measurement of
nonheme storage iron
• Provides information on
liver histology/pathology
• Positive correlation with
morbidity and mortality
• Invasive, painful procedure
associated with potentially
serious complications
• Risk of sampling error,
especially in patients with
cirrhosis
• Requires skilled
physicians and
standardized laboratory
techniques
Noninvasive Measurement of
Liver Iron
• SQUID
– Measures paramagnetic properties of liver iron
– 4 operational machines worldwide
• MRI techniques
– Potentially widely available
– Gradient echo (T2*)
 Insensitive at levels >15 mg/g1
– Spin echo (T2)(R2)
 Linear over larger range, longer acquisition time2
– Gradient with SIR3
– Spin echo with SIR4
SQUID = superconducting quantum interface device; MRI = magnetic resonance imaging;
SIR = signal intensity ratio.
1. Anderson LH, et al. Eur Heart J. 2001;22:2171. 2. St. Pierre TG, et al. Blood. 2005;105:855.
3. Gandon Y, et al. Lancet. 2004;363:357. 4. Jensen, et al. Blood. 2003;101:4632.
SQUID Biomagnetic Susceptometer
Superconductive Quantum Interference Device
Resistance (ohm)
Superconductivity
Conductive
0.8
0.26
0.2
0.16
0.1
0.06
00
2
Superconductive
4
6
temperature (°K)
8
Meissner effect
T>Tc
T<Tc
T<Tc
Normal
Flux expulsion
Persistant current
(nonsuperconducting)
(superconducting state)
(superconducting state)
Josephson effect
V
S
I S
I
-Ic
SQUID Thalassaemia Center. Turin, Italy
Courtesy of A. Piga, Turin Thalassaemia Centre.
Ic
LIC Assessment by SQUID
Advantages
Disadvantages
• Linear correlation with LIC
assessed by biopsy
• May be repeated frequently
• Indirect measurement of
LIC
• Limited availability
• High cost
• Highly specialized
equipment requires
dedicated technician
• Not validated for LIC
assessment and may
underestimate levels
LIC = liver iron concentration; SQUID = superconducting quantum interference device.
Quantitative Iron
Assessment by MRI
T2 (heart, liver)
Spin echo, gradient-echo sequences
Signal intensity ratio (SIR)
R2 (liver)
Gradient-echo sequences
s-1
T2*(heart)
Gradient-echo sequences
ms
Liver R2 images
and distributions
for a healthy
volunteer and 3
iron-loaded
subjects with
sequentially
increasing liver
iron concentrations
St Pierre TG, et al. Blood. 2005;105:855.
R2 MRI—A New Measure for LIC
Mean Transverse Relaxation Rate
<R2> (s-1)
300
250
Hereditary
haemochromatosis
200
-thalassaemia
50
-thalassaemia/
haemoglobin E
40
Hepatitis
150
100
30
50
20
0.5
1.0
1.5
2.0
0
0
10
20
30
40
50
Biopsy Iron Concentration (mg/g-1 dry tissue)
R2 MRI is a validated and standardized method for measuring LIC.
This technique is now approved by TGA and FDA and in the EU
St Pierre TG, et al. Blood. 2005;105:855.
R2* (Hz)
R2* Measurement of LIC
Estimated HIC (mg/g dry weight)
HIC = hepatic iron concentration.
Wood JC, et al. Blood. 2005;106:1460.
MRI Assessment of LIC
Advantages
Disadvantages
• Assesses iron content
• Indirect measurement of
throughout the liver
LIC
• Potentially widely available
• Requires MRI imager with
• Pathologic status of liver and
dedicated imaging method
heart can be assessed in
parallel
Liver iron levels can be assessed using a technique known as R2 (spin echo) MRI,
which is a validated and standardized method for measuring LIC
MRI = magnetic resonance imaging; LIC = liver iron concentration.
Assessing Cardiac Function and
Iron Load
Monitoring—Heart
• Rhythm
– Resting or exercise ECG
– 24-hr Holter monitoring
• Left ventricular function
– ECHO
– Quantitative sequential (MUGA or MRI)1
– Wall motion abnormalities
• Heart “iron”
– T2*2
– SIR (T2 weighted)3
ECG = electrocardiogram; ECHO = echocardiogram; MUGA = multiple gated acquisition;
MRI = magnetic resonance imaging; SIR = signal intensity ratio.
1. Davis BA, et al. Blood. 2004;104:263. 2. Anderson LH, et al. Eur Heart J. 2001;22:2171.
3. Jensen P, et al. Blood. 2003;101:4632.
T2* MRI: Emerging New Standard
for Cardiac Iron
90
80
LVEF (%)
70
60
50
Cardiac T2* value of
37 in a normal heart
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90
100
Heart T2* (ms)
Relationship between myocardial T2* values and left ventricular ejection
fraction (LVEF). Below a myocardial T2* of 20 ms, there was a progressive
and significant decline in LVEF (R = 0.61, P < .0001)
Photos courtesy of Dr. M. D. Cappellini.
Anderson LJ, et al. Eur Heart J. 2001;22:2171.
Cardiac T2* value of
4 in a significantly
iron overloaded
heart
Cardiac T2* and Risk for Cardiac
Dysfunction
• In a study of 67 patients with thalassaemia
major, 5 had systolic dysfunction LVEF <56%
• All 5 patients also had myocardial T2*
significantly <20 msec (the lower limit of
normality)
Westwood MA, et al. J Magn Reson Imaging. 2005;22:229.
No Correlation of Heart Iron Concentration
with Liver Iron Concentration?
Anderson LJ, et al. Eur Heart J. 2001;22:2171.
MRI Assessment of Cardiac Iron
Advantages
Disadvantages
• Rapidly assesses iron
content in the septum of
heart
• Iron levels can be quantified
reproducibly
• Functional parameters can
be examined concurrently
• Pathologic status of liver and
heart can be assessed in
parallel
• Indirect measurement of
cardiac iron
• Requires MRI imager with
dedicated imaging method
• Technically demanding
• Methodology remains to
be standardized and
validated
Cardiac iron levels can be rapidly and effectively assessed using a technique
known as T2* (gradient echo) MRI, which is becoming the new standard method
MRI = magnetic resonance imaging.
Tools for Monitoring
Iron Overload
Prognostic significance demonstrated
• Serum ferritin (= body iron)1
• Liver iron (= body iron)2
• Heart function (LVEF)3
1. Olivieri NF, et al. Blood. 1994;84:3245. 2. Brittenham G, et al. N Engl J Med. 1994;331:567.
3. Davis BA, et al. Blood. 2004;104:263.
Tools for Monitoring
Iron Overload
Prognostic significance not yet demonstrated
• Cardiac iron (T2*), linked to LVEF1
• NTBI, LPI
– LPI measures the redox-active component of
plasma iron2
– Can form reactive radicals responsible for many
clinical consequences of iron overload2
1. Anderson LJ, et al. Eur Heart J. 2001;22:2171.
2. Esposito BP, et al. Blood. 2003;102:2670.
Iron Overload Evaluation
Recommendations
1. Do not use a single test alone for iron overload management
2. Exclude haemochromatosis
3. Serum ferritin is the basic parameter, but
a) Do not use it alone
b) Be aware of its poor predictive value
c) Use the trend of repeated measures (iron load direction)
4. Measure liver iron concentration (iron load amount and “buffer reserve”)
a) By biopsy, if indicated
b) By SQUID, where available
c) By MRI (method, calibration, error)
5. Assess the heart iron by MRI T2* (cardiac risk), at least once
a) If positive, use it as the main result to set treatment
b) If negative, do not exclude body iron overload
6. In transfused patients
a) Record accurately the iron input
b) Do iron balance, where feasible
7. Integrate the available tests to manage properly iron chelation
Angelucci E, et al. Haematologica. 2008, in press.