Whole blood and serum blood are two different substances commonly used to determine the blood alcohol content of a person. Both come from drawing blood from someone although serum blood is more heavily processed. You will want to understand the differences between whole blood and serum blood especially in relation to blood alcohol content testing.
Understanding Whole Blood
Whole blood means that the sample that was drawn has not been unnecessarily processed. The blood that is drawn by a technician is technically whole blood. One major difference is that the vial used to collect whole blood will contain a small amount of an anti-clotting agent. This agent stops the blood that was drawn from clotting and turning into a thick substance that cannot be tested or processed. Another difference is that whole blood contains less water than serum making it thicker.
Understanding Serum Blood
Serum blood is drawn in the same way as whole blood. The difference is that there is no anti-clotting agent in the container holding the blood. This means that the blood will begin to clot relatively quickly. The blood is placed onto a centrifuge and spun around. This causes the blood in the container to start to separate. The denser clotted areas move the bottom of the container. A lighter yellowish liquid forms on the top. This thin liquid is called the serum. Serum is not as thick as whole blood. It contains more water. The serum can be extracted from the container and then used for testing with special equipment.
Differences in Testing Techniques
Whole blood and serum blood are tested for alcohol or other substances in different ways. Whole blood is fed into a specific type of machine that extracts the blood alcohol content quickly. Serum blood is tested using different equipment. Only the serum is tested. This is because many of the pieces of equipment used for blood alcohol testing are unable to handle the density of whole blood. The serum is preferred in some cases because it moves more easily through the equipment. One issue is that the higher water content of serum blood provides elevated blood alcohol readings when compared to whole blood. This means the results of a serum blood alcohol test need to be adjusted by around 18 percent in order to get results that are more accurate.
Challenging the Results
There are many ways to challenge the results of both whole blood and serum blood tests in court. Serum blood tests can be challenged because of the number used to adjust the results. This number of called the conversion factor. The factor might not be accurate. Another way to challenge the results is to look at the certifications of the lab. Labs must be individually certified for both whole blood and serum blood testing. If the lab does not have the certification for the type of test performed, then the test might not be valid. Challenging the state and accuracy of the equipment is common as well since contamination and small mistakes could artificially increase the blood alcohol content reported. It is important to talk to a lawyer when whole blood or serum blood tests are performed.