Conditions for Ensuring Reliable Results in the Laboratory

Laboratory test results often play an important role in diagnosing diseases or disorders in the function of the body’s various systems. Confidence in test results means that a sample whose true results are normal is not reported as abnormal for any reason, and, conversely, that abnormal results are not reported as normal.

The accuracy of a test result depends on several factors, some of which are mentioned here:

1. Selection of the type of test

2. Patient preparation

3. Type of collection tubes (e.g., serum or plasma) and labeling the tube with the patient’s personal information (first name, last name, and date of birth)

4. Adding special substances to the sample (e.g., anticoagulants or preservatives)

5. Correct sample collection (care in selecting the vein, duration of tourniquet application, etc.)

6. Storing the sample under specific conditions until testing

7. Performing the test and validating the results

8. Interpretation of test results

Apart from patient preparation, test selection, and the interpretation of results, which are carried out by the treating physician, a large share of the factors affecting test accuracy (factors 2 to 8) relates to the laboratory. In sum, various disruptions or errors that lead to incorrect results can occur at any of the stages above, so results that do not match the patient’s clinical picture are not necessarily the fault of the laboratory. Given the extraordinary number of compounds that can now be measured in body fluids, and the very different methods used to measure them, it is not possible to describe and present all the factors that affect test results.

For the laboratory, in order to prevent errors and mistakes, it is necessary that a written procedure exist for each test and that attention be paid to the details of potential interfering factors. The table below lists the factors that must be observed during the patient preparation stage, in other words, before sample collection.

# Condition

1 Diet

2 Fasting for 8 to 12 hours

3 Sample collection with the patient lying down, after 30 minutes of calm rest, or after two hours of being awake or at rest

4 Specifying the time of sample collection, or specific days of the menstrual cycle and other matters related to hormones

5 No tea, coffee, or tobacco use

6 No alcohol consumption

7 Discontinuing certain medications before sample collection, with the approval of the treating physician

8 Attention to physical activity, such as exercise

9 No intramuscular injections before the test

10 Correct procedure for complete urine collection over a specified period

Table 1: Conditions to be considered before sample collection, depending on the needs and type of test.