Anemia

Introduction

Anemia is defined for patient care as a reduction in one or more of the major red blood cell measurements obtained as part of the complete blood count.

• Hemoglobin concentration
• To convert to mmol/L, the hemoglobin in g/dL can be multiplied by 0.62.
• Hematocrit
• Also called packed cell volume.
• Is the percentage of blood cell volume occupied by red blood cells.
• Red blood cell count

A low hemolobin concentration and/or low hematocrit are the parameters most widely used to diagnose anemia. WHO criteria for anemia in adults are

• Females - Hemoglobin <12 g/dL or hematocrit <36%
• Males - Hemoglobin <13 g/dL or hematocrit < 39%

NOTE: Reticulocytes are immature red blood cells.

Symptoms

Most patients with mild or early-stage anemia are asymptomatic.

If anemia becomes severe and/or prolonged, the lack of oxygen in the blood can lead to classic symptoms of fatigue, weakness, shortness of breath, exercise intolerance, headache, dizziness, anorexia and/or pallor.

If sudden blood loss occurs, the patient can experience symptoms, such as chest pain, fainting, palpitations and tachycardia.

Patients with vitamin B12 deficiency can present with neurologic symptoms, including peripheral neuropathies, visual disturbances and/or psychiatric symptoms.

Causes

Anemia can occur due to

• Impaired red blood cell production (e.g. sickle cell disease, thalassemia)
• Increased red blood cell destruction (e.g. hemolysis)
• Blood loss (e.g. heavy menses, melena)
• Nutritional deficiencies (e.g. iron, folate, vitamin B12)
• As a complication of another medical disorder (e.g. chronic kidney disease or a malignancy)
• Drug-induced

Evaluation Based on MCV

The type and cause of anemia cannot be determined based on signs and symptoms alone.

The mean corpuscular volume (MCV), which reflects the size or average volume of red blood cells, can help determine the type of anemia and the possible underlying cause.

Relevant laboratory tests are useful for further evaluation.

• Iron studies - microcytic anemia
• Iron studies include serum iron (bound to transferrin), serum ferritin (iron stores), transferrin saturation (amount of transferrin binding sites occupied by iron) and total iron binding capacity (amount of transferrin binding sites available to bind iron or unbound sites).
• Vitamin B12 and folate levels - macrocytic anemia
• Reticulocyte counts - measure of red blood cell production

External Links

• UpToDate - Diagnostic Approach to Anemia in Adults
  
• WHO - Anaemia