Use of biological sample banks in epidemiological studies.

Serum and urine banks have proved to be useful in the conduct of epidemiological studies. Samples collected as part of a large prospective study can be stored and retrieved later for laboratory analyses, selecting samples from groups of special interest and also from matched controls. The applications of the method are considered under three headings: firstly as a marker of a medical disorder, secondly as a measure of the extent of exposure to a harmful agent and thirdly as a direct measure of a suspected harmful or protective agent. Examples of each are given. Banks of biological samples other than serum or urine, such as hair and nail, are now being formed. The scientific opportunities of these collections are great and it will be of interest to see how they will be used.