How are blood samples collected in clinical trials?

Laboratory tests are often performed as part of the safety assessment in clinical trials of unlisted drugs. Blood samples are used for clinical biochemistry and hematology tests, and sometimes to determine the concentration of the drug being tested. In addition to safety assessment, laboratory tests may be used to evaluate efficacy (e.g., blood glucose levels in food and urine disease trials).

Blood samples can be collected in a variety of ways. Usually a syringe or vacuum tube is used. Laboratories undertaking large projects tend to use vacuum tubes. The investigator should generally be provided with a blood collection kit that includes a box, a set of labels, a needle, a syringe cartridge, and a number of blood collection tubes. Each blood collection tube is evacuated and sealed with a rubber stopper, labeled, and placed in the box after collection and transported directly to the laboratory. Sometimes the blood sample should be centrifuged before transportation.

The quality of the blood sample is critical. It is the responsibility of the test coordinator to ensure that blood samples are collected and transported in accordance with the requirements. Common problems with blood samples are as follows:

l Inadequate sampling equipment;

l Incorrect timing of sampling or failure to meet fasting requirements;

l Blood samples placed at excessive temperatures or delayed transportation;

l Wrongly labeled or unlabeled blood collection tubes;

l Blood samples or documentation that are not labeled with the time or the subject's unique code;

l the blood sample was collected in the incorrect volume (too little or too much).