Current trends and problems in health screening.

Automation in clinical chemistry is a powerful tool. Like most innovations it is posing many questions as well as resolving some. Its use in population screening has led to questioning the validity of the old system of ;normal values' and to the search for better methods of indicating the significance of laboratory tests. This in itself is likely to have a good effect in that it is leading to a rigorous examination of the clinical value in diagnosis of the ever increasing number of laboratory tests.The ease and cheapness with which laboratory screening can be carried out is in itself a danger; it can readily lead to an increasingly large diagnostic effort but diminishing returns, including some inconvenience or even harm to a fair proportion of the people screened. It is, therefore, important to examine thoroughly, through population surveys and intervention studies, the validity of all novel forms of prescriptive screening, including those of clinical chemistry. Cheapness of testing needs to be examined in the wider context of the overall cost-effectiveness of screening.