Anemia

S. Shekar Chakravarthi

Anemia is defined as a reduction of more than 10% below mean values in the quantity or quality of the concentration of red blood cells (RBC) or circulating hemoglobin. In 1972, the World Health Organization standardized the normal hemoglobin values for men and women as 13 g/dl and 12 g/dl, respectively. Variations for age include children aged 6 months to 2 years, 10.5 g/dl; 2 to 12 years, 11.5 g/dl; in men aged more than 65 years, a 1 to 2 g/dl decline may be seen, probably because of decreased androgen production (1).

 
I. Approach

A. Classification. Anemia can be categorized based on the size of the RBCs (mean corpuscular volume, MCV) or the cause of the anemia:

1. Size. Microcytic (MCV < 80 FL); normocytic (MCV 80 to 100 FL); macrocytic (MCV > 100 FL).

 2. Etiology.

a. Hypoproliferative or caused by decreased red cell production from:

 i. Reduced iron supply (e.g., blood loss, chronic inflammation, or malnutrition)

ii. Decreased stimulus (e.g., renal disease or hypothyroidism)

iii. Marrow defect (e.g., drugs, fibrosis, or tumors)

b. Hemolytic or caused by red cell destruction (e.g., decreased red cell survival time)

i. Immunologic: idiopathic or secondary to drugs

ii. Extrinsic: mechanical or caused by a lytic substance

c. Ineffective hematopoiesis

i. Megaloblastic anemias (abnormality in nuclear maturation)

 ii. Thalassemia and sideroblastic anemia (abnormality at cytoplasmic maturation).

3. Worldwide, the most common type of anemia results from iron deficiency. Among hospitalized patients, the most common form is anemia of chronic disease.

 B. Screening for anemia. Patients at risk, where screening may prove useful, include those who are institutionalized, of African descent, have poor nutritional status, and those who have had a gastrectomy (2).

 
II. History. The severity of symptoms is directly related to the rapidity of anemia development. Fatigue and a decreased level of activity may be noticed with mild anemia. In those with cardiovascular disease, angina, palpitations, or dyspnea on exertion, headaches or dizziness may be the presenting symptom. In the elderly, the symptoms may be more subtle and vague. Other relevant history includes the use of prescription and over-the-counter medications, exposure to toxic agents or chemicals (e.g., lead), alcohol use, history of cancer, history of surgery, type of diet, and a family history of anemia. In younger women, menstrual and reproductive histories will be helpful.

 
III. Physical examination. The patient may appear pale, tachycardia may be present unless blocked by a drug, and the patient may have orthostatic hypotension. A systolic murmur may be heard. Dark stool that is hematoccult positive suggests gastrointestinal bleeding. Jaundice can indicate increased red cell destruction. Bone tenderness, lymphadenopathy, splenomegaly, or neurologic signs can suggest diagnoses such as multiple myeloma and other malignancies, hypersplenism, or vitamin B₁₂ deficiency.

 
IV. Testing. Complete blood count with red cell indices, reticulocyte count, and peripheral blood smear examination is the initial step, and subsequent workup will depend on these results. The red cell indices along with the red cell distribution width (RDW) (normal, = 13 ± 1.5) will help to differentiate anemias (Table 16.1).

 
V. Diagnostic assessment. In iron deficiency anemia, the serum iron and ferritin level will be low with an elevated total iron binding capacity (TIBC). In some cases, ferritin can be falsely elevated as an acute phase reactant. Also, with adequate iron replacement therapy, a rise of 2 g/dl in hemoglobin can be expected in 3 weeks (3).

In contrast, in anemia of chronic disease the TIBC is not elevated, ferritin is normal, serum iron may be low or normal, and the hemoglobin is usually more than 8 g/dl. Subacute or chronic inflammation can cause sideropenic anemia; nonsideropenic anemias can result from kidney, liver, thyroid, or adrenal failure.

Depending on the history, a lead level may be indicated, especially in children (4). Hemoglobin electrophoresis is performed when sickle cell traits or thalassemias are suspected. Decreased plasma haptoglobin, elevated serum lactate dehydrogenase, and hemoglobinuria can indicate increased intravascular hemolysis; a positive Coombs’ test indicates immune-mediated red cell destruction. Premature destruction can occur from prosthetic valves, G-6-PD or pyruvate deficiency, or it can be drug induced or caused by cold or warm antibodies.

In macrocytic anemias a serum Vitamin B₁₂, folate, and thyroid stimulating hormone may be checked. Other causes include leukemias, hemolytic anemia, alcohol, or drugs.

Indications for a bone marrow aspiration include pancytopenia, presence of immature cells in the peripheral blood, or an unexplained normocytic anemia (5). Marrow biopsy is considered if aspiration is unsuccessful or if myelofibrosis or metastatic cancer is suspected.

References

1. Welborn JL, Meyers FJ. A three point approach to anemia. Postgrad Med 1991;89(2):
179–183, 186.

2. Farley PC, Foland J. Iron deficiency anemia: how to diagnose and correct. Postgrad Med 1990;87(2):89–93, 96, 101.

3. Massey AC. Microcytic anemia: differential diagnosis and management of iron deficiency anemia. Med Clin North Am 1992;76(3):549–566.

4. Kline NE. A practical approach to the child with anemia. J Pediatr Health Care 1996;10(3):99–105.

5. Colon-Otero G, Menke D, Hook CC. A practical approach to the differential diagnosis and evaluation of the adult patient with anemia. Med Clin North Am 1992;
76(3):581–597.

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Book Source Details

• Book Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
• Author(s): Robert B. Taylor (editor)
• Year of Publication: 2000
• Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2000 Lippincott Williams & Wilkins.

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