Evaluation of laboratory tests in hospitals.

The use of laboratory tests in the management of 174 randomly selected patients admitted as acute medical emergencies was monitored in detail. The occasions when a test result changed patient management, and the nature of that change, were noted. Tests were classified according to information yielded and the importance of any action taken. For biochemistry alone every test result was costed. A ranking for all tests was produced, in terms of expected actions per test, and for biochemistry a 'value for money' table giving actions per pound spent. Every test request was classified as either discretionary or non-discretionary. The discretionary category was further subdivided into diagnostic and monitoring. The values, in terms of action-producing results, of non-discretionary, diagnostic, and monitoring tests were compared, and this comparison showed that the cost per item of helpful information was about 10 pounds for diagnostic, 23 pounds for monitoring, and 20 pounds for non-discretionary tests. In total, 1790 pounds was spent, and 28 items of unique information were yielded, enabling clinicians to discharge five patients, take seven courses of action which would have had serious consequences if omitted, and 16 actions the omission of which would have led to very serious consequences.