Pourquoi privilégier l'urine par rapport au sang ?

Vulgarisations

Why choose urine over blood?

April 26, 2024

Urine and blood are two different bodily fluids that can provide valuable information about a person's fitness or health, but they are often analyzed for different reasons depending on the needs.

Urine

Urine tests play a crucial role in various areas of health, from diagnosing and treating diseases, examining organ function, detecting drug use, assessing hydration and physical stress, to confirming pregnancy. As a direct reflection of the substances present in the blood, urine offers a wealth of information about our state of health. This ability stems largely from the importance of the kidneys in the elimination process, which allows substances that are soluble in water or made soluble by chemical reactions to be excreted in the urine.

Urine tests are mainly based on the assessment of the chemical composition of urine, including the detection of molecules such as sugar, proteins, ketones, etc. In addition, urine tests can identify the abnormal presence of cells (blood, white blood cells, epithelial cells, etc.) and microorganisms (bacteria, yeast, etc.). The presence of these elements in urine can reveal various health problems such as diabetes, urinary tract infections, as well as liver or kidney disorders; but also reveal important information related to the impact of the environment on the body, for example when performing physical exercises, exposure to specific environmental conditions (altitude, extreme heat/cold, etc.). Urine examination also provides information on the concentration of these dissolved molecules, cells and microorganisms as well as their degree of dilution in urine, which can help assess, among other things, kidney function and the body's hydration level.

As for the collection, urine is collected by the patient in a sterile container, usually at home or in a laboratory. The sample is then sent to the laboratory for analysis.

The blood

Blood tests, like urine tests, can be used to detect drug use, the presence of abnormalities in the blood, improve training and recovery during physical exertion, detect certain nutritional deficiencies, diagnose certain illnesses and assess organ function.

Blood analysis often includes an assessment of blood components such as red blood cells, white blood cells and platelets, as well as parameters such as hemoglobin, hematocrit and erythrocyte indices, ..., but it is also prescribed to assess the levels of various biochemical substances such as sugar, lipids (cholesterol, triglycerides), liver enzymes (ALAT, ASAT), markers of renal function (urea, creatinine), ... The analysis therefore helps to provide information on metabolisms and organ functions, and to diagnose a wide range of medical conditions such as cardiovascular diseases, liver diseases, autoimmune diseases, infections, hormonal disorders, cancers, and many others. Blood analysis may also include immune tests such as lymphocyte count, measurement of specific antibodies, ... which can help diagnose autoimmune disorders, infections, or even allergies. It also helps to support athletes in their training and nutrition programs to help them perform to the best of their abilities. It is the health professional who determines the analyses to be carried out, taking into account the objective allocated to the blood test.

The blood test is most often carried out in a specialized laboratory.

In summary

Urine analysis focuses primarily on the components and characteristics of the urinary system, while blood analysis provides a more holistic view of the body's health, including information about blood flow, metabolisms, and the immune system. The main differences include:

Specific information: Urine and blood provide different information about a person's health. For example, a urine test can detect the presence of certain substances such as proteins, red blood cells, bacteria, or abnormal cells, which may indicate kidney, urinary, or other problems, while a blood test can assess the levels of these substances.
Non-invasive: Urine sample collection is generally less invasive than blood sample collection, making it easier for patients to perform, less stressful, and less painful.
Fast: Urine collection is done with minimal preparation and can easily be incorporated into daily routine, unlike blood sampling which requires going to the laboratory.
Cost: Urine tests can often be less expensive than blood tests, making them a more economical option for certain screening or follow-up tests.
A regular resource available: an adult produces between 1.5L and 2L of urine per day, which corresponds to 5-7 urinations per day, or a volume of 200 to 250mL/urination. It is therefore easier to perform a urine test than a blood test.
Health monitoring: Some diseases or conditions can be more easily monitored through urine analysis. For example, people with diabetes can monitor their blood sugar using special urine test strips. It is also possible to use these analyses to monitor your personal health during a physical training program (preparing for a competition, optimizing training and recovery, etc.) as well as to monitor your nutrition in order to highlight the diet applied in order to improve it according to needs (for physical training, in the event of a deficiency, etc.).
Early detection: In some cases, substances or cells present in urine can be a means of early detection of diseases or health problems, particularly when a low quantity of molecules is present in the blood.

However, it is important to note that urine and blood tests are often complementary and can be done in parallel to get a more complete picture of a person's health or fitness. Decisions about which tests to perform often depend on the patient's symptoms, medical history, and the recommendations of the treating physician.

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