Anaemias Information Source
Anemia or anaemias, from the Greek (ναιμία ) meaning "without blood", refers to 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 hypoxia; since all human cells depend on oxygen for survival, varying degrees of anemias 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 body 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). In menstruating women, dietary iron deficiency is a common cause of deficient red blood cell production.
Anemia is the most common disorder of the blood. There are several kinds of anemia, produced by a variety of underlying causes. 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 "kinetic" approach which involves evaluating production, destruction and loss, and 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 more rapidly to expose cases where multiple causes of anemia coexist.
Signs and Symptoms of Anemia or Anaemias
Anemia goes undetected in many people, and symptoms can be vague. Most commonly, people with anemia report a feeling of weakness or fatigue, general malaise and sometimes a poor concentration. People with more severe anemia often report dyspnea (shortness of breath) on exertion. Very severe anemia prompts the body to compensate by increasing cardiac output, leading to palpitations and sweatiness, and to heart failure.
Pallor (pale skin, mucosal linings and nail beds) is often a useful diagnostic sign in moderate or severe anaemia, but it is not always apparent. Other useful signs are cheilosis and koilonychia.
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Diagnosis of Anemia or Anaemias
Generally, clinicians request complete blood counts in the first batch of blood tests in the diagnosis of a suspected anaemia. Apart from reporting the number of red blood cells and the hemoglobin level, the automatic counters also measure the size of the red blood cells by flow cytometry, which is an important tool in distinguishing between the causes of anemia. Examination of a stained blood smear using a microscope can also be helpful, and is sometimes a necessity in regions of the world where automated analysis is less accessible.
In modern counters, four parameters (RBC Count, hemoglobin concentration, MCV and RDW) are measured, allowing others (hematocrit, MCH and MCHC) to be calculated, and compared to values adjusted for age and sex. For males, the hemoglobin level that is suggestive of anemias is usually less than 13.0 g/dl, and for females, it is less than 12.0 g/dl.
Reticulocyte counts, and the "kinetic" approach to anemia, have become more common than in the past in the large medical centers of the United States and some other wealthy nations, in part because some automatic counters now have the capacity to include reticulocyte counts. A reticulocyte count is a quantitative measure of the bone marrow's capacity to produce new red blood cells. The reticulocyte production index is a calculation of the ratio between the level of anemia and the extent to which the reticulocyte count has risen in response, thus indicating whether a "normal" reticulocyte count actually may reflect an inadequate response to anemia.
If an automated count is not available, a reticulocyte count can be done manually following special staining of the blood film. In manual examination, activity of the bone marrow can also be gauged qualitatively by subtle changes in the numbers and the morphology of young RBCs by examination under a microscope. Newly formed RBCs are usually slightly larger than older RBCs and show polychromasia. Even where the source of blood loss is obvious, evaluation of erythropoiesis can help assess whether the bone marrow will be able to compensate for the loss, and at what rate.
When the cause is not obvious, clinicians use other tests to further distinguish the cause for anemias. A clinician may also decide to request other blood tests that might identify the cause of fatigue; serum glucose, ESR, ferritin, serum iron, RBC folate level, serum vitamin B12, renal function tests (e.g. serum creatinine) and electrolytes may be part of such tests. When the diagnosis remains difficult another test the bone marrow biopsy can be used to assesses the bone marrow more directly.