Total iron-binding capacity TIBC

Determinations of plasma Iron, total Iron-binding capacity (TIBC), and % transferrin saturation... 

Hematological Methods. Hematological analyses can Include the determination of the total hemoglobin concentration (In g%), the packed cell volume (PCV In %), the red blood cell count (In 10 /mm ) and reticulocytes count (In %), calculation of the red cell Indices, examination of a blood film, tests to demonstrate the presence of Inclusion bodies and of sickle cells, tests to evaluate the distribution of fetal hemoglobin (Hb-F) Inside the red cells, the red cell osmotic fragility, the concentration of serum Iron (SI), total Iron binding capacity (TIBC), and the survival time of the red cells. Details of all... 

Decreased red blood cell (RBC) count, hemoglobin (Hgb) and hematocrit (Hct) iron metabolism may also be altered [iron level, total iron binding capacity (TIBC), serum ferritin level, and transferrin saturation (TSAT)]. Erythropoietin levels are not routinely monitored and are generally normal to low. Urine positive for albumin or protein. 

Total iron-binding capacity (TIBC) 220-420 mcg/dL (39.4-75.2 pmol/L) Measures the capacity of transferrin to bind iron high in iron-deficiency anemia. 

The earliest and most sensitive laboratory change for iron-deficiency anemia is decreased serum ferritin (storage iron), which should be interpreted in conjunction with decreased transferrin saturation and increased total iron-binding capacity (TIBC). Hb, hematocrit, and RBC indices usually remain normal until later stages of iron-deficiency anemia. 

Under normal circumstances, transferrin is one-fourth to one-third saturated with iron. The level of saturation may decrease in systemic infection or cancer and in iron deficiency anemia, the most common nutritional deficiency in the United States. In individuals with iron deficiency anemia, transferrin levels are increased. The level of saturation with iron increases in iron overload syndromes such as hereditary hemochromatosis or as a result of repeated blood transfusions, as is the case in thalassemia patients. Determinations of total plasma iron (TI) and plasma total iron binding capacity (TIBC) are routinely performed in the clinical biochemistry laboratory. The TIBC value reflects transferrin levels in plasma the amount of iron that can be bound by transferrin is equal to TIBC x 0.7. Total plasma iron levels in iron deficiency anemia become abnormal before hemoglobin levels show any change. 

The diagnosis of HH is established based on serum transferrin saturation (TS), defined as serum iron divided by total iron binding capacity (TIBC). Since serum iron and ferritin levels lack specificity for diagnosis when used alone, measurement of fasting TS is currendy recommended as a first screen to detect iron overload. TS is the best indirect biochemical marker of iron stores. A fasting TS of greater than 45% will detect over 98% of all cases of phenotypic hemochromatosis (Tavill, 2001). 

The total iron-binding capacity (TIBC) of transferrin can be calculated from the transferrin concentration in pg/dl or pmol/l transferrin x 1.41 or transferrin x 25.2. This gives a normal value for men of 268-436 pg/dl or 48-78 pmol/l and for women of 257-402 pg/dl or 46-72 pmol/l. The difference between TIBC and the amount of iron found before Fe and magnesium carbonate are added is called free iron-binding capacity. This is the FIBC which is possible beyond the normal saturation capacity of about one third of the transferrin. The transferrin saturation (in %) can be calculated as follows serum iron (pg/dl) x 100 divided by transferrin (mg/dl) x 1.25. T free IBC of < 50 figldl, i. e. transferrin saturation of >62%, suggests the presence of HC. 

Because of the convenience of simultaneous measurement of serum iron and total iron binding capacity (TIBC) and the desirability of knowing percent saturation of Tf (see Chapter 31), Tf is sometimes estimated indirectly from the TIBC value by the following equation ... 

The serum unsaturated iron binding capacity and total iron binding capacity (TIBC) are determined by addition of sufficient Fe to saturate iron binding sites on transferrin. The excess Fe " is removed (e.g., by adsorption with light magnesium carbonate [MgCOs] powder), and the assay for iron content is then repeated. From this second measure-... 

Iron deficiency anemia (IDA) is characterized by decreased levels of ferritin (most sensitive marker) and serum iron, as well as decreased transferrin saturation the Hgb and hematocrit (Hct)fall late in the disease. Total iron-binding capacity (TIBC) is increased. RBC morphology includes hypochromia and microcytosis. Most patients with IDA are adequately treated with oral ferrous (Fe +) sulfate therapy, although parenteral iron therapy is necessary in select patient populations. 

TFN is a glycoprotein that binds and transports ferric iron to the liver and reticuloendothelial system for storage. As a surrogate marker of nutrition status, it is more likely to decrease in response to protein depletion before serum ALB concentrations decrease because it has a shorter biologic half-life (8 days), and there is less of it in the body (less than 100 mg/kg of body weight). Serum TFN concentrations may be determined by direct measurement or can be estimated indirectly from measurement of total iron-binding capacity (TIBC), where TFN = (TIBC x 0.8) — 43. Critical illness, hydration status, and iron stores affect the serum TFN concentration. In iron deficiency, hepatic TFN synthesis is increased, resulting in increased sermn TFN concentrations unrelated to protein stams. 

Total iron binding capacity (TIBC) of a serum specimen is an indirect measure of transferrin concentration, although in some laboratories transferrin can be measured directly. Normally transferrin is around 30% saturated with iron. When this falls to less than 15%. iron deficiency is likely and. some degree of clinical effect can be expected. A high percent saturation is the most sensitive marker for iron overload. Like serum iron, transferrin is decreased as part of the acute phase response. Protein-energy malnutrition also decreases transferrin synthesis by the liver and hence its serum concentration. 

Iron SC Deferoxamine causes 15% lowering of total iron-binding capacity (TIBC) lavender-top Vacutainertube contains EDTA, which lowers total iron. 

A. Specific levels. If the total serum iron level is higher than 450-500 mcg/dL, toxicity is more likely to be present. Semm levels higher than 800-1000 mcg/dL are associated with severe poisoning. Detenriine the serum Iron level at 4-6 hours after ingestion, and repeat determinations after 8-12 hours to rule out delayed absorption (eg, from a sustained-release tablet or a tablet bezoar). The total iron-binding capacity (TIBC) is unreliable In Iron overdose and should not be used to estimate free iron levels. 

Figure 5. Plasma Iron and Total Iron Binding Capacity (TIBC) of Rabbit Plasma Before and After Infection with Pasteurella Multocid,a. Percentages at Top of Bars Indicate Percent Saturation of Serotransferrin with Iron. Reprinted with Permission from Kluger and Rothenburg (1979). Copyright by American Association for the Advancement of Science.

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