Yield of routine annual laboratory screening in the institutionalized elderly.

We examined the yield of a battery of 19 screening laboratory tests performed routinely in 70 functionally intact patients, averaging 82.6 years of age and residing at a chronic care facility. The 70 patients underwent 3,903 screening tests (70 admission batteries and 156 batteries at annual intervals). Twenty per cent of the admission test results and 17 per cent of all subsequent annual test results were "abnormal". "New abnormal" results (previously unknown to the responsible physicians) occurred primarily in five of the 19 screening tests; they were found in 13 per cent of all admission screening tests and in 6 per cent of all annual tests. However, many of the "new abnormalities" were only minimally outside the normal range, and only 26 (0.7 per cent) led to further diagnostic evaluation. Of these 26, only four (0.1 per cent of all tests ordered) led to changes in patient management, none of which benefited the patient in an important way.