If the body's temperature can vary from minute to minute, it should come as no surprise that the chemicals and enzymes that are measured can also vary with similar rapidity. Some values, such as blood glucose, will directly be influenced by a recent intake of a meal. Other values, such as magnesium, are less likely to be affected. All of these conditions which may alter the laboratory value before the actual blood sample or specimen is taken are known as pre-analytical variables . Careful attention to potential pre-analytical variables can often resolve puzzling laboratory values.
Errors can occur, however.
The prudent course of action is always to repeat the laboratory test to ensure that the value which was first reported is accurate. If the two values differ significantly, sometimes an additional sample can be requested. Statistical terms can very confusing. The Doctor's Doctor has provided a short primer of some of the terms. These two terms describe similar concepts and are related.