Practical advice before taking a laboratory test to help avoid variations in the results
The purpose of the Clinical Laboratory is to offer results that support the doctor in the prevention, diagnosis and timely treatment of diseases. In order to adequately respond to this purpose, it is necessary that all phases of assistance are carried out taking into account the existence of various variables specific to each patient that have a significant influence on the final quality of the Outcome.
These variables are traditionally known as preanalytic conditions, some as age, gender, race and pregnancy, can not be modified, so the doctor must know them to properly interpret the results; However, there are other variables that can be modified with the correct preparation of the patient and are the first steps to obtain valid results.
Prior to carrying out the tests in an ideal way, the patient must contact the clinical laboratory, where they will receive additional and detailed information about the necessary preconditions to perform the sample collection.
Usually, a minimum fasting period is recommended for routine blood sampling that varies according to the test, for example:
8 hours fast
- Folic acid
- Apo A1 and Apo B
- Glucose tolerance curves
- Serum iron
- Growth hormone
- Peptide C
- B12 vitamin
12 hour fast
- HDL and LDL cholesterol
- Total lipids
During the fast it is only allowed to drink water (not coffee, tea, juices or diet drinks).
It is important to avoid blood sampling after long periods of fasting (above 16 hours) and in the case of tests that do not require fasting, it is recommended to wait at least 2 hours after food intake.
For taking urine and feces samples, it is recommended to use clean or sterile vials (in case of culture), plastic, wide mouth and screw cap to avoid spills. It is very important to avoid contamination of stool urine samples or vice versa. If the sample is taken outside the laboratory, it should be sent as soon as possible at room temperature within the 2 hours after the take.
In general, the day before conducting laboratory tests should avoid:
- Intense physical activity (heavy work, sports, etc.).
- Changes in the usual diet (except for tests that require a particular diet).
- Drinking alcohol
- Stressful situations (sleep at your usual time and plan everything so that day is not anxious).
Other causes that may cause variations in the results of laboratory tests are certain diagnostic procedures such as the administration of contrasts for imaging tests, performing rectal examination and some therapeutic procedures, such as hemodialysis and blood transfusion.
To access the service of our laboratory is not necessary to make a prior appointment, you can submit from Monday to Friday, from 6:30 a.m. to 8:00 p.m. in the main building from 6:30 a.m. to 6:00 p.m. in the Primary Care Sample Taking Unit and Saturdays from 7:00 a.m. to 12:00 p.m. in both. Remember that you must present the medical indication, identity card or identity document and your medical insurance card if you are affiliated with any.
Finally, keep a good communication with laboratory personnel, request clear instructions and if necessary written, to help ensure the quality of your results.