Infant 1yr

Dietary Iron 30%

Loss

Recycled Iron 70%

Figure 5.2 Iron need versus amount of recycled iron available.

Loss

Recycled Iron 70%

Table 5.5 O Stages of Iron Deficiency Anemia Matched to Diagnostic Signals

Stage 1: Iron Stores Depleted. Test for

Absence of stainable bone marrow iron Decreased serum ferritin level Increased TIBC

Stage 2: Iron-Deficient Erythropoiesis. Test for

Slight microcytosis Slight decreased hemoglobin Decreased transferrin saturation Stage 3: Iron Deficiency Anemia. Test for

Decreased serum iron Decreased serum ferritin Increased TIBC

Decreased transferring saturation one of the most sensitive indicators of iron stores, with a normal value of 20 to 250 pg/L for men and 10 to 120 pg/L for women. Ferritin is an acute phase reactant, and conditions such as chronic inflammation or chronic infection may falsely elevate the serum ferritin level. In these cases, an accurate assessment of iron stores will be difficult. The TIBC measures the availability of iron binding sites on the transferrin molecule. If an individual is iron deficient, there will be many binding sites available searching for iron and the TIBC

Figure 5.2 Iron need versus amount of recycled iron available.

the platelet count will be elevated. The MCV and MCHC will be markedly lower than normal, the RDW may be mildly elevated, and the peripheral smear will show small red cells, which are deficient in hemoglobin. Target cells and elliptocytes may occasionally be seen (Fig. 5.4). The reticulocyte count will be low in comparison to the level of anemia, indicating a slightly ineffective erythropoiesis.

Tests to assess a patient's iron status include serum iron, serum ferritin, transferrin or total iron binding capacity (TIBC), and transferrin saturation. Serum iron is a measure of the total amount of iron in the serum with a normal value of 50 to 150 pg/L. Serum ferritin is

Table 5.6 O Causes of Iron Deficiency Anemia

Related to Increased Iron Demands

Growth spurts in infants and children

Pregnancy and nursing Related to Lack of Iron Intake

Poor diet

Conditions that diminish absorption Related to Blood Loss Menorrhagia

Gastrointestinal bleeding (GI bleed) Hemolysis

Other physical causes of bleeding

70 Part II • Red Cell Disorders

70 Part II • Red Cell Disorders

Figure 5.3 Koilonychia.

value will be increased. This value is elevated in iron-deficient patients (reference range, 250 to 450 pg/L) but subject to fluctuations in patients who use oral contraceptives or have liver disease, chronic infections, or nephrotic syndrome. The TIBC is less sensitive to iron deficiency and must be evaluated in terms of the patient's other health issues. Transferrin saturation (% saturation) is derived as the product of the serum iron concentration divided by the TIBC and multiplied by 100. The normal value is 20% to 50%.

There are occasions when a diagnosis of IDA is made too casually and is based on a patient's age group, gender, or vague complaints. Young women who give a history of fatigue or menstrual problems are often simply given a trial of iron therapy with no supporting laboratory workup. A diagnosis of IDA should be made ONLY with the supporting laboratory data that reflect the patient's red cell and iron status. The patient should insist that this work be done before therapy is initiated as unnecessary iron use has the potential for serious consequences.

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