Anemia overview
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Anemia main page |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Anemia is the most common disorder of the blood. Anemia, from the Greek (Template:Polytonic) (an-haîma) meaning "without blood", is a deficiency of red blood cells (RBCs) and/or hemoglobin. This results in a reduced ability of blood to transfer oxygen to the tissues, causing tissue hypoxia. Since all human cells depend on oxygen for survival, varying degrees of anemia can have a wide range of clinical consequences. Hemoglobin (the oxygen-carrying protein in the red blood cells) has to be present to ensure adequate oxygenation of all tissues and organs.
The three main classes of anemia include excessive blood loss (acutely such as a hemorrhage or chronically through low-volume loss), excessive blood cell destruction (hemolysis) or deficient red blood cell production (ineffective hematopoiesis). Anemia is defined as a hemoglobin concentration (Hb) of less than 12 g/dL in women and less than 13 g/dL in men or hematocrit of 36% in women and 40% in men.
Classification
Anemia can be classified in a variety of ways, based on the morphology of RBCs, underlying etiologic mechanisms, and discernible clinical spectra, to mention a few. There are two major approaches of classifying anemias. The first is the "kinetic" approach, which involves evaluating production, destruction, and loss. The second is the "morphologic" approach, which groups anemia by red blood cell size. The morphologic approach uses a quickly available and cheap lab test as its starting point (the MCV). On the other hand, focusing early on the question of production may allow the clinician to more rapidly expose cases where multiple causes of anemia coexist.
Pathophysiology
Erythropoietin produced in the kidneys are the major stimulant of red blood cell (RBC) production as a response to anemia. Erythropoietin is stimulated by tissue hypoxia, that in turn stimulates erythroid progenitor cells to proliferate. The EPO levels follow a reverse relationship with the hemoglobin levels. Thus, in normal hosts, low levels of hemoglobin are associated with high levels of EPO. However, in patients with chronic kidney disease and anemia of chronic diseases the response may not be as strong as seen in patients without these comorbidities.
Causes
The causes of anemia can be divided based on the mean corpuscular volume into microcytic, macrocytic, and normocytic anemia. The common causes of microcytic anemia are iron deficiency, thalassemia, anemia of chronic disease, and sideroblastic anemia (congenital, lead, alcohol, drugs). Common causes of macrocytic anemia includes alcohol abuse, folic acid deficiency, vitamin B12 deficiency, myelodysplastic disorders, acute myeloid leukemias, drug-induced anemia (eg,hydroxyurea, AZT, chemotherapeutic agents), reticulocytosis, and liver disease. The common causes of normocytic anemia includes: acute blood loss, anemia of chronic disease, bone marrow suppression, chronic renal insufficiency,hypothyroidism, and hyperthyroidism
Diagnosis
History and Symptoms
Anemia goes undetected in many people, and symptoms can be vague. The signs and symptoms are similar in different types of anemia. The presentation may vary depending on the acuteness of onset, hematocrit levels, and the general health conditions of the patient (age, sex, pregnancy, cardiac conditions, and any other comorbidities) rather than only the etiology behind the anemia. A hematocrit level of between 30 - 35 usually produces no symptoms whereas, a fall of heamtocrit levels to 15 - 20 may produce severe symptoms (shortness of breath, syncope). However, most patients will experience some symptoms related to anemia when the hemoglobin level reaches 7 g/dL.
Physical Examination
Anemia goes undetected in many people, and symptoms can be vague. The signs and symptoms are similar in different types of anemia. The presentation may vary depending on the acuteness of onset, hematocrit levels, and the general health conditions of the patient (age, sex, pregnancy, cardiac conditions, and any other comorbidities) rather than only the etiology behind the anemia. A hematocrit level of between 30 - 35 usually produces no symptoms whereas, a fall of heamtocrit levels to 15 - 20 may produce severe symptoms (shortness of breath, syncope). However, most patients will experience some symptoms related to anemia when the hemoglobin level reaches 7 g/dL.
Laboratory Findings
For adult men, a hemoglobin level less than 13.0 g/dl is diagnostic of anemia, and for adult women, the diagnostic threshold is below 12.0 g/dl. Complete blood counts is the first test to be done. The CBC measures different values like mean Corpuscular Volume (important tool in differential diagnosis of anemia), red blood cells,hemoglobin, and Red blood cell distribution width or RDW). These values allow others values for instance (hematocrit, Mean corpuscular hemoglobin or MCH and mean corpuscular hemoglobin concentration or MCHC) to be calculated.
Treatment
Primary Prevention
Consumption of food rich in iron is essential to prevention of iron deficiency anemia. Some foods rich in iron include: Canned clams; Fortified dry cereals; Cooked oysters; Organ meats (liver, giblets); Fortified instant cooked cereals; Soybeans, mature, cooked; Pumpkin and squash seed kernels, roasted; White beans; Blackstrap molasses, 1 Tbsp; Lentils, cooked;Spinach, cooked from fresh; Beef (chuck); Kidney beans; Sardines; Beef(rib); Chickpeas; Duck, meat only; Lamb shoulder; Prune juice.Certain foods have been found to interfere with iron absorption in the gastrointestinal tract, and these foods should be avoided in persons with established iron deficiency. They include tea, coffee, wheat bran, rhubarb, chocolate, chewing gum, red wine, and dairy products.[1]