A complete blood count (CBC) is the most accessible method for the initial assessment of the state of the body, the results of which, along with a general urine test and a biochemical blood test, are included in the diagnostic algorithms for most diseases.
The blood composition is relatively constant, but it reacts to almost any pathological changes in the body. In order to understand what is happening with a person, and what studies to prescribe in the future, or decide on treatment, the doctor, first of all, always prescribes an OAC.
This study is also used as a preventive examination even in the absence of any symptoms and reflects changes in health status. In addition, the CBC allows doctors to evaluate the success of the treatment.
Blood consists of a liquid part (plasma) and shaped elements (cells) and performs a huge number of different functions such as transporting oxygen and carbon dioxide, maintaining a constant body temperature, stopping bleeding, neutralizing pathogens, etc.
The changes observed in the blood reflect the general condition of the body.
Fluctuations in the parameters of the general blood test can also occur normally, under the influence of various factors: food intake, physical activity, emotional stress, pregnancy, smoking, etc.
Thus, in pregnant women, the number of red blood cells and hemoglobin normally decreases. The number of white blood cells, in turn, may increase after eating, exercising, or prolonged exposure to the sun.
When is a general blood test ordered?
Most often, a doctor prescribes a general blood test in order to assess the levels of hemoglobin, red blood cells, platelets, ESR, the number of leukocytes, and the leukocyte formula.
So, for example, if there are signs of infection, a general blood test will help to understand the nature of the pathogen: viral or bacterial. In particular, a viral infection is characterized by an increase in the level of lymphocytes, and for bacterial infection – neutrophils.
Also in the general blood test, the number of red blood cells, hemoglobin, and hematocrit are determined. These indicators allow you to identify and assess the severity of anemia, as well as suggest the cause of its occurrence.
Another important indicator is platelets.
These small cells are direct participants in the processes of blood clotting. If the platelet count is low, the risk of bleeding and bruising increases. In a situation where there are a lot of platelets, the likelihood of blood clots and, as a result, blockage of blood vessels increases.
The erythrocyte sedimentation rate
The erythrocyte sedimentation rate (ESR) is a measure of how quickly blood separates into plasma and cells in a test tube.
The main factor affecting this ESR is the protein composition of the blood, which, in turn, changes under various physiological (pregnancy, menstruation) and pathological (inflammation, infections) conditions.
Together with other blood parameters, ESR has prognostic value and can serve as an indicator of the effectiveness of the treatment. At the same time, an increase in ESR is not a specific indicator of any disease and does not directly correlate with the dynamics of the disease that has arisen.
This is due to the fact that from the onset of the disease it can take from 24 to 48 hours before the ESR value goes beyond the normal range, and also because the ESR can remain at a high level for up to several months even after the symptoms disappear.
There are automated and manual methods for determining the ESR. Different laboratories may use different methods, which is why it is important to understand that ESR results from different laboratories can only be similar at normal ESR values.
If the ESR is higher than normal, then the analysis data may not be comparable, even if the study was conducted at the same time. The higher the ESR level, the greater the difference between the results obtained using different methods.
For the correct interpretation of the tests, experts advise always taking tests in the same laboratory.
Where to take a general blood test?
Use Google to search for blood work near you.
In a medical laboratory, a complete blood count is performed from venous (through a vein puncture) and capillary (finger puncture) blood. Blood from a vein is the “gold standard” of biological material for complete blood count and is preferred.
The fact is that unlike venous, capillary blood is a mixture of blood from small arteries, veins, and capillaries, containing intercellular fluid, the remains of destroyed cells, and lymph, which can affect the result of the analysis.
In some cases, capillary blood donation is still recommended: with a tendency to venous thrombosis, overweight and difficult access to veins, and extensive burns, in young children.
It is important to remember that only a doctor can correctly interpret changes in the results of the study, recommend additional diagnostic methods, including laboratory ones, to clarify the existing blood picture, and prescribe effective treatment and prevention methods.
Do not self-diagnose, seek help from a specialist!