Sampling

General information on urine extraction

In order to minimize sources of error, a correct procedure for sampling is necessary. The following points should therefore be followed in principle:

• The urine sample should be taken directly in the doctor’s office to keep the time to analysis as short as possible.
• Precise instructions should be given for the extraction of urine.
• Physical effort should be avoided before sampling or during collection.
• In women, no urine testing should be carried out during or shortly after menstruation, as contamination of the urine with blood leads to erroneous results.
• Single-use containers should be used for urine extraction.
• To avoid confusion, samples should be carefully labelled immediately with the patient’s full name, first name and date of birth, as well as the date of collection.

Most microbiological studies require the extraction of mid-beam urine. Proper sample collection technique is necessary to avoid contamination by germs from the areas of the external sex organs.

The intended sampling should be carried out as follows.

• For most examinations, the first morning urine is required
• To do this, the hands must be carefully washed with soap and water
• Thorough cleaning of the genitals with hand-warm water without soap
• Dry area around the urethral opening with swab

Urine extraction:

• Do not use the first portion of the urine, but let it run into the toilet
• Collect the second (medium) portion (in adults about 10 – 20 ml) in the provided sterile urine cup without interrupting the urine ray
• Avoid contamination of the inside of the cup by hands or clothing as far as possible
• Let the rest of the urine run back into the toilet
• Close the urine cup well and keep cool

Normally, however, it is the case that, for example, in a doctor’s office, the patient gets a cup pressed into his hand with the hint that please fill the cup, but if possible not completely to the edge. And that was often the complete instruction. As a result, the probability of relevant contamination of the sample is relatively high. How many false-positive or false-negative test results result from this has not yet been scientifically proven.