Medical blood test to measure transferrin
Total iron-binding capacity
(
TIBC
) or sometimes
transferrin iron-binding capacity
is a medical laboratory test that measures the blood's capacity to bind
iron
with
transferrin
.
[1]
Transferrin
can bind two atoms of
ferric iron
(Fe
3+
) with high affinity. It means that
transferrin
has the capacity to transport approximately from 1.40 to 1.49 mg of
iron
per gram of
transferrin
present in the blood.
[2]
It is performed by
drawing blood
and measuring the maximum amount of iron that it can carry, which indirectly measures
transferrin
[3]
since transferrin is the most dynamic carrier. If TIBC values are known, the transferrin concentration can be estimated with the following formulas:
[2]
- Transferrin (mg/dL) = 0.8 x TIBC (μg of iron/dL) ? 43
- Transferrin (mg/dL) = 0.7 x TIBC (μg of iron/dL)
To measure TIBC in the blood is less expensive than a direct measurement of
transferrin
.
[4]
[5]
The TIBC should not be confused with the
unsaturated iron-binding capacity
or
UIBC
(
LOINC
2501-5
,
22753-8
&
35216-1
). The UIBC is calculated by subtracting the serum iron from the TIBC.
[6]
Interpretation
[
edit
]
Taken together with
serum iron
and
percent transferrin saturation
clinicians usually perform this test when they are concerned about
anemia
,
iron deficiency
or
iron deficiency anemia
. However, because the
liver
produces transferrin, alterations in function (such as
cirrhosis
,
hepatitis
, or
liver failure
) must be considered when performing this test. It can also be an indirect test of liver function, but is rarely used for this purpose.
[7]
The percent transferrin saturation (i.e., the result of the formula of serum iron/TIBC x 100) can also be a useful indicator. Studies also revealed that a transferrin saturation (serum iron concentration ÷ total iron binding capacity) over 60 percent in men and over 50 percent in women identified the presence of an abnormality in iron metabolism (hereditary hemochromatosis, heterozygotes and homozygotes) with approximately 95 percent accuracy. This finding helps in the early diagnosis of hereditary hemochromatosis, especially while serum
ferritin
still remains low. The retained iron in hereditary hemochromatosis is primarily deposited in parenchymal cells, with reticuloendothelial cell accumulation occurring very late in the disease. This is in contrast to transfusional iron overload in which iron deposition occurs first in the reticuloendothelial cells and then in parenchymal cells. This explains why ferritin levels remain relative low in hereditary hemochromatosis, while transferrin saturation is high.
[8]
[9]
Condition
|
Serum iron
(highly variable)
|
Transferrin and TIBC
|
Percent transferrin saturation
|
Iron deficiency anemia
|
Low
|
High. The
liver
produces more transferrin, presumably attempting to maximize use of the little iron that is available.
|
Low, as there is insufficient iron.
|
Anemia of chronic disease
|
Low, as the body holds iron intracellularly with
ferritin
.
|
Low. The body produces less transferrin (but more ferritin), presumably to keep iron away from
pathogens
that require it for their metabolism. This is mainly regulated by increased
hepcidin
production.
|
Normal
|
Pregnancy
or use of
hormonal contraception
, but without iron deficiency
|
Normal
|
High. The liver increases the production of transferrin, thus raising TIBC.
|
Low, as there is excess transferrin with normal serum iron levels.
|
These examples demonstrate that to properly understand a value for TIBC, one also must know the serum iron, the percent transferrin saturation, and the individual clinical situation. In modern laboratory testings, serum ferritin levels are generally accepted as reliable single indicators of the presence of iron deficiency.
[
citation needed
]
Usual values
[
edit
]
Laboratories often use different units of measurement and "normal ranges" may vary by population and the laboratory techniques used. Look at the individual laboratory
reference values
to interpret a specific test (for instance, your own).
[
citation needed
]
Example reference ranges are:
μg/dL = micrograms per deciliter; μmol/L = micromoles per litre.
References
[
edit
]
- ^
"MedlinePlus Medical Encyclopedia: Total iron binding capacity"
. Retrieved
2008-12-31
.
- ^
a
b
"MrLabTest: Normal TIBC level in the blood"
. Retrieved
2020-11-19
.
- ^
Yamanishi H, Iyama S, Yamaguchi Y, Kanakura Y, Iwatani Y (January 2003). "Total iron-binding capacity calculated from serum transferrin concentration or serum iron concentration and unsaturated iron-binding capacity".
Clin. Chem
.
49
(1): 175?8.
doi
:
10.1373/49.1.175
.
PMID
12507977
.
- ^
Kasvosve I, Delanghe J (October 2002). "Total iron binding capacity and transferrin concentration in the assessment of iron status".
Clin. Chem. Lab. Med
.
40
(10): 1014?8.
doi
:
10.1515/CCLM.2002.176
.
PMID
12476940
.
S2CID
45447911
.
[
permanent dead link
]
- ^
Gambino R, Desvarieux E, Orth M, et al. (December 1997).
"The relation between chemically measured total iron-binding capacity concentrations and immunologically measured transferrin concentrations in human serum"
.
Clin. Chem
.
43
(12): 2408?12.
doi
:
10.1093/clinchem/43.12.2408
.
PMID
9439462
.
- ^
"Iron Transport"
. Retrieved
2008-12-31
.
- ^
Khare S, Garg VK, Jatav O.
"Serum Iron and TIBC Parameters in Chronic Liver Disease"
(PDF)
. Retrieved
2020-11-19
.
- ^
https://aasld2014.uberflip.com/i/581653/0
[
dead link
]
- ^
"Hemochromatosis - AASLD Hemochromatosis"
.
- ^
a
b
Harrison's Principles of Internal Medicine. 17th Edition (2008). Pg. 2432 (Table 351-2)
External links
[
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]