Anemia - Diagnosis

Reticulocyte Count. Reticulocytes are immature red blood cells, and their count reflects the rate of red blood cell production. The upper normal limit is about 100,000/mL. A low count, when bleeding isn't the cause, suggests problems in production in the bone marrow. An abnormally high count indicates that the red blood cells are being destroyed in high numbers and indicates hemolytic anemia. New research suggests that the reticulocyte hemoglobin content (CHr) test may be more accurate than a standard hemoglobin test for detecting iron deficiency in infants. This test may help identify babies who are at risk for becoming anemic and help them get treated earlier.

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Blood Morphology. A blood smear viewed under a microscope allows an expert to classify the blood by its color, size, and shape (its morphology ). Generally red blood cells are categorized as:

Pale-colored (hypochromic) and abnormally small (microcytic).
Normal colored and normal sized (normochromic, normocytic).
Abnormally large (macrocytic).

The shape of the red blood cells, which can be distorted in many blood disorders, is also important in determining a diagnosis.

Diagnosing Iron Deficiency Anemia and its Causes

There are two steps in making diagnosis in patients with symptoms of iron deficiency anemia:

The first step is to determine if a person is actually deficient in iron.
If iron stores are low, the second step is to diagnose the cause of the iron deficiencies, which will help determine treatment.

Determining if Iron Stores are Low. The following findings are important in determining that a person is iron deficient:

Blood cells viewed under the microscope are pale (hypochromic) and abnormally small (microcytic). They are also mostly uneven in shape. (These findings suggest iron deficiency, they but can also appear in anemia of chronic disease and thalassemia.)
Hemoglobin and iron levels are low. (These findings further suggest iron deficiency, but they can also occur in cases due to anemia due to chronic disease.)
Ferritin levels are low. Ferritin is a protein that binds to iron. Low levels typically mean reduced iron stores. High ferritin levels in the blood do not always mean sufficient iron stores. For example, pregnant women may have high ferritin levels into their third trimester but still be iron deficient. Ferritin levels may also be normal or even elevated in patients with inflammation from anemia of chronic disease, even if they also have low iron stores.
In children with iron deficiencies, reticulocytehemoglobin levels are low. Reticulocytes are immature red blood cells and this test may be the most effective approach for diagnosing iron deficiency in children.
A test that measures a factor called serum transferrin receptor (TfR) is proving to be very sensitive in identifying iron deficiency in problematic patients, including the elderly with chronic diseases and possibly pregnant women. (It is often very difficult to identify iron deficiencies in patients who also have anemia of chronic diseases because their ferritin levels are often normal or even high.) For example, levels of TfR are high in patients with ACD and iron deficiency anemia, but they are normal or only slightly raised in ACD alone. The test is expensive, however, and some experts recommend it should be used only when there is a high suspicion of iron deficiency in the elderly.
Measuring erythrocyte zinc protoporphyrin (ZPP), a product of abnormal heme synthesis, is under investigation and may prove to be a simple and precise measure of iron deficiencies, particularly in children.