1 Anemia

Start with the blood count

Anemia is a reduction in hemoglobin or red blood cells that can limit oxygen delivery to tissues. The first step in evaluation is a complete blood count (CBC), including the mean corpuscular volume (MCV). The reticulocyte count and targeted tests then help identify the cause.

Use results to narrow the cause

Use the MCV to classify the anemia, then interpret the reticulocyte count and other test results to distinguish reduced red-cell production from blood loss or hemolysis. No single finding should be interpreted in isolation: for example, low serum iron alone does not establish iron deficiency, so assess it alongside ferritin and total iron-binding capacity (TIBC).

Recognize iron deficiency

A typical iron-deficiency pattern includes low hemoglobin, low MCV, low ferritin, low serum iron, and high TIBC. When iron deficiency is found in an older adult, investigate its cause, including possible gastrointestinal blood loss, as well as replacing iron.

Interpret the inflammation pattern

Inflammation can restrict iron availability. Anemia of inflammation may show low serum iron and low TIBC with normal-to-high ferritin, unlike the typical iron-deficiency pattern. Thus, low iron alone is not enough to diagnose iron deficiency.

Distinguish B12 and folate deficiency

Vitamin B12 deficiency can cause macrocytic anemia and neurologic symptoms, including numbness in the feet and difficulty with balance. Folate deficiency can also cause macrocytosis and fatigue, but neurologic symptoms are generally absent in folate deficiency. Laboratory evaluation helps establish the cause; assess for B12 deficiency before treating with folate alone.

Identify red-cell destruction

An increased reticulocyte count, elevated indirect bilirubin and lactate dehydrogenase (LDH), and low haptoglobin indicate hemolysis, or increased red-cell destruction. Reticulocytes rise as the marrow responds to red-cell loss. These findings support hemolytic anemia, but further tests are needed to determine its specific cause.

Consider bone-marrow failure

Low counts of red cells, white cells, and platelets together with fatigue, frequent infections, or easy bruising should raise consideration of aplastic anemia. This condition involves bone-marrow failure; evaluation may include bone-marrow testing.

Account for kidney disease

Chronic kidney disease can contribute to normocytic anemia with a low reticulocyte count. A likely mechanism is reduced erythropoietin signaling and red-cell production. Treatment depends on the cause and clinical assessment; anemia alone does not establish that iron or another therapy is indicated.

Match treatment to the cause

Treatment depends on the type, cause, and severity of the anemia. Treat the identified cause: iron is appropriate when iron deficiency is established, while other causes require different management. Do not give iron automatically for every anemia, and do not treat all macrocytic anemia with folate alone. Blood transfusion is reserved for selected clinical situations rather than being the routine first treatment for mild anemia.

• Iron-deficiency anemia