Overview of anemia
Anemia affects millions of people worldwide. The National Center for Health Statistics estimated that 3.4 million Americans are living with anemia.1
Nevertheless the actual anemic individuals may be even greater as anemia is often under-diagnosed and under-treated.
Anemia is one of the most prevalent public health problems in most of the developing countries and has serious consequences on national development.
Iron deficiency anemia (IDA) is the most common nutritional deficiency and is one of the leading risk factors for disability and death worldwide, affecting an estimated two billion people.2
Although anemia is usually a consequence of many diseases including chronic inflammatory, infectious or neoplastic disorders, it may also occur from the treatment of the disease itself. Anemia may affect school children, adolescents, elderly and reproductive-age women.
It has serious negative consequences including
- increased mortality in women and children,
- reduced capacity to learn
- and decreased productivity in all individuals.
Anemia in the elderly is linked to an increase in morbidity and mortality.3 Pregnant women often show IDA as a consequence of increased plasma volume during pregnancy. Gynecological anemia is often caused by hypermenorrhea (increased menstrual bleeding).4
Treatment should be directed at the cause of the anemia. This article will discuss in detail regarding the different classes and types of anemia, the causes, the risk factors and the diagnosis and management strategies for anemia of various origin.
Classification of anemia
Anemia can be classified by cytometric methods, based on the morphology of red blood cells (RBCs), erythrokinetic schemes (the rates of RBCs production and destruction) and biochemical or molecular methods (the etiology of the anemia at the molecular level).
In the morphological approach, anemia is classified by the size of RBCs on microscopic examination of a peripheral blood smear. The size is reflected in the mean corpuscular volume (MCV). The amount of hemoglobin relative to the size of the cell (hemoglobin concentration) per RBC is known as mean corpuscular hemoglobin concentration (MCHC) and mean cell hemoglobin (MCH), which reflects the hemoglobin amount per RBC.
The cytometric classifications are as following:
Normochromic, Normocytic Anemia
This anemia shows normal MCHC and normal MCV. This results the following:
- Anemia of chronic disease (ACD)
- Hemolytic anemia (HA)
- Anemia of acute hemorrhage
Hypochromic, Microcytic Anemia
This anemia shows low MCHC and low MCV. This results the following following:
- Iron deficiency anemia
Normochromic, Macrocytic Anemia
This anemia shows normal MCHC and high MCV. This results the following:
- Vitamin B12 deficiency
- Folate deficiency
The erythrokinetic classification is based on the rate of RBCs turnover. If this rate is high, a normoregenerative anemia occurs which are seen in hemolysis (excess destruction of RBCs) or hemorrhage (loss of RBCs from the vascular compartment).
In these cases, the bone marrow responds by increasing the production of RBCs and releasing them into the bloodstream prematurely.
Several lab tests can help to determine the increased RBCs turnover such as:
- Reticulocyte count
- Serum unconjugated bilirubin and urine urobilinogen concentration
- Serum haptoglobin concentration
- Bone marrow biopsy
This categorization is based on the etiology of the anemia (will be discussed below). In a typical case of IDA, the biochemical indicators include serum iron, serum transferrin, transferrin saturation, serum ferritin and serum circulating transferrin receptor.
Generally, biochemical tests are aimed at identifying a depleted cofactor necessary for normal production of RBCs (iron, ferritin, folate and vitamin B12), an abnormally functioning enzyme (glucose-6-phosphate dehydrogenase, pyruvate kinase), or abnormal function of the immune system (Coombs test).
Symptoms of anemia
Symptoms of anemia vary depending on the severity of the condition. Symptoms can sometimes be vague and be detected only during a clinical examination and investigation.
In general, the symptoms and signs of anemia may include the following:
- Generalized weakness and fatigue
- Shortness of breath (dyspnea) on exertion
- Rapid heartbeat (palpitation)
- Poor concentration
- Ringing in the ears (tinnitus)
- Irritability and other mood disturbances
- Mental confusion
- Loss of sexual drive
- Pale skin and mucosal linings
- Koilonychia (flattened and brittle nails)
- Enlarged spleen
Pica, defined as the craving or compulsive ingestion of non-food substances such as earth, clay, chalk, wax, soap and grass may be a symptom of IDA, although it may also occur in those who have normal levels of hemoglobin.6
Iron deficiency had also been shown to contribute to the pathophysiology of attention-deficit hyperactivity disorder (ADHD) in children.7 Chronic anemia may result in behavioral disturbances and reduced academic performance in children of school-going age.
Anemia, which is severe will trigger a compensatory mechanism in the body which responds by increasing the cardiac output, leading to heart failure. The incidence of anemia in patients with heart failure is as high as 50%. Although the causes are multifactorial, inflammation appears to be the primary cause of anemia in heart failure, along with effects from increased plasma volume, effects of drug therapy and other complications of heart disease.8
Causes of anemia
Defined as a decrease in RBCs’ mass, anemia is a symptom of disease that requires investigation to determine the underlying etiology.
There are three major causes of anemia:
- Excessive loss of RBCs that seen following trauma or in women during their reproductive years.
- Abnormally rapid destruction of RBCs within the body (hemolysis) that exceeds the replacement ability of bone marrow.
- Deficient RBCs production (ineffective hematopoiesis) due to inadequate intake or poor utilization of dietary iron as seen in malnutrition or helminth (hookworm) infestations.
Other significant causes of anemia include nutritional deficiencies other than iron deficiency (folic acid and vitamin B12 deficiencies), genetic conditions (thalassemia, sickle cell anemia (SCA) or hemoglobinopathies), factors related to reproduction (obstetric complications, gynecological disorders), chronic diseases and malignancies (kidney disease or neoplasia), infections (HIV/AIDS, tuberculosis, hepatitis and malaria) and drug or chemical induced anemia.
The anemia that accompanies infection, inflammation and cancer is commonly termed as ACD.5
Risk Factors for anemia
The contributing social causes for the development of anemia, particularly among the anemia prone population in developing countries include the following:
- Poverty leading to inability to buy healthy foods or foods with adequate amounts of absorbable iron or to obtain nutritional supplements.
- Low use of antenatal services providing nutritional supplements during pregnancy.
- Lack of trained birth attendants to manage bleeding during delivery.
- Poor sanitation conditions.
- Lack of access to health services that prevent and manage hookworm infestation.
- Exposure to and accidental ingestion of heavy metals particularly lead, as lead interferes with iron absorption and hemoglobin production.
- Poor knowledge on the importance of anemia and anemia prevention and control interventions.
- Practices that restrict food intake including poor infant breastfeeding practices.
- Inadequate introduction of fortified complementary foods for infants and children.
- Vegetarian diet.
- Blood donation more than two units per year in women and three units per year in men.
Diagnosis of anemia
Anemia is diagnosed based on the patient's symptoms and from various laboratory tests.9 As anemia is best defined in relation to hemoglobin (Hb) and hematocrit (HCT) levels below the normal reference range, the first test used to diagnose anemia is a complete blood count (CBC).
Anemia is diagnosed when the Hb and HCT readings are as below:
- Men: Hb is <13 g/dL and HCT is between 41 and 53%.
- Women: Hb is <12 g/dL and HCT is between 36 and 46%.
- Children aged 6 months to 6 years: Hb <11 g/dL.
- Children aged 6 –14 years: Hb <12 g/dL.
Other common blood investigations include the following:
- Peripheral blood smear
- Reticulocyte count
- Serum iron and transferrin level
- Serum folate and vitamin B12
- Serum bilirubin
- Stool analysis
- Hemoglobin electrophoresis
- Liver function tests
- Bone marrow biopsy
- Endoscopy to detect gastrointestinal bleeding
Treatment and Prevention of anemia
Treatment is directed at the cause of the anemia. Severe anemia is life-threatening and can be treated in the hospital with blood transfusions. The treatment of different types of anemia will be discussed in detail in their respective topics.
In general, depending upon the cause and severity, treatment of anemia may include the following:
- Nutritional supplements—iron, vitamin B12 or folic acid.
- Dietary change.
- Treatment of underlying disorder.
- Treatment with erythropoietin injections.
- Transfusion of packed RBCs for patients who are actively bleeding and for patients with severe, symptomatic anemia.
- Corticosteroids are useful in the treatment of autoimmune HA.
- Splenectomy is useful in the treatment of autoimmune HA and in certain hereditary hemolytic disorders.
Many kinds of anemia, particularly those caused by nutritional deficiencies may be prevented by consuming a diet rich in those deficient nutrients or by taking the appropriate supplements.
Other types of anemia can be prevented by treating the underlying cause for the condition such as an internal bleeding or chronic worm infestation.
Some forms of hereditary anemia such as SCA cannot be prevented, therefore it is important to have the appropriate investigations for diagnosis and to follow specific directions for treatment.
By implementing below mentioned programs by all sectors including health professionals, government and non-governmental organizations we can better prevent anemia.
- Raising awareness of anemia prevention and control.
- Promoting behavior change in the community.
- Adequate training among health workers.
- Advocating for increased funding for national anemia programs.
These strategies are most effective when approached in a coordinated and targeted manner.
You May Also Like To Read
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Written by: healthplus24.com team
Date last updated: December 10, 2014