Blood tests: when and how?

You have your prescription, you have made an appointment in a laboratory service ... but you do not know yet why the doctor has prescribed these analyzes? No need to panic. Here are the explanations.
When performing a blood test?

Blood tests include not only components of the blood but also all substances carried in the blood. The dosages of these substances have respective meanings on the state of health of an individual.

The blood tests can be performed at any age, according to indications.

It is useful in many circumstances, but only a doctor can assess the need for:

In case of disease (acute or chronic) to guide the diagnosis and investigate the causes for the monitoring of changes to the choice of appropriate treatment for the control and treatment effectiveness

If the patient's complaints or anomalous signs in an individual: fever, fatigue, gastrointestinal bleeding ...

If medication long way to evaluate drug toxicity in some organs

As part of a health check (usually done once a year)

In case of routine analysis

In case of detection of an infectious disease, a hereditary disease, a genetic disease ...

How does a blood test?

Terms and preparations

A blood test is necessarily prescribed by a doctor.

There are certain types of tests that require the patient be fasting (eg glucose). This means that the patient should not eat or drink 12 hours before the blood test. Indeed, taking the meal could alter the results of the assays.

However, some types of blood tests may be preceded by a light breakfast.

In case of continuous treatment, the medication depends on the type of test to be performed. In general, bacteriological examinations require the cessation of antibiotic drugs to better detect the agent.

Tobacco and alcohol should be avoided before a blood test.

All this information is necessarily mentioned by the laboratory service when making appointments.

The day of the exam ...

It is necessary to always have in itself the prescription even if the blood test is done by appointment.

A blood test is very simple and fast. It is done in a sitting position. The puncture is most often achieved at the antecubital vein. A tourniquet is placed a little higher. A needle connected to a sample tube, * is introduced at the elbow to collect the blood. The amount of blood collected is the number of analyzes to be performed.

A tight pack is placed at the puncture site after the blood to stop the flow of blood.

The blood in small children is more difficult and requires more suitable hardware. The hygiene and disinfection are rigorous in a blood test.

After the blood test, the tube is loaded labeled then be analyzed.

The analysis ...

Blood testing is usually carried out by biologists. Some require specialized structures and must be performed in a hospital facility. Other tests also use more sophisticated equipment automatically displays the results.

The result

The results of blood tests are generally known a few days after the blood test. They are sent directly to the prescribing physician.

Normal values are given in the result (still range), in front of the value corresponding to that of the patient. This is to facilitate the interpretation of the doctor. However, these values are only indicators because depend on the technical and analytical protocol used by the laboratory. Thus, these values can vary from one laboratory to another.

It is noted, however, that the biological values vary depending on factors such as

Sex

Age

Medication

The pace of life: stress, fatigue, difficult to digest or high fat meal ...

Pregnancy ...

All these factors are taken into account when interpreting the results. Thus, whatever our way of understanding a blood test, the interpretation is necessarily the role of the physician.

The blood test helps the doctor to guide diagnosis. However, the interpretation of a blood test alone can not provide information on the disease. In fact, the prescription of these blood tests is justified by specific guidance and interpretation must be consistent with the clinical context and other tests.
* Sample tube: an anticoagulant substance is sometimes in the tube prior to sampling in order to maintain the quality of the blood. This condition is particularly necessary for the CBC and the balance of hemostasis.