Why do serum and plasma levels have to be “corrected” mathematically?
Just think of the old child’s tale about the crow who tried to drink from a pitcher of water while perched on its edge. When the crow put his beak in the pitcher, the water level was too low for him to drink. He then obtained a number of pebbles and dropped them in the pitcher. As more pebbles were dropped into the pitcher, the water level rose and eventually, the crow was able to drink from the pitcher. The red blood cells have the same effect in blood. They artificially increase the volume of fluid in whole blood just as putting ice in a glass of water is likely to cause the water to overflow. Therefore, the alcohol in plasma and serum alcohol samples are “more concentrated” than blood because the red blood cells have been removed and the values must be “corrected” to represent a value that would have been obtained from whole blood. Remember, BAC stands for Blood Alcohol Concentration, and concentration is described in percent which is defined as weight per volume. Percent means part
