Iatrogenic disorders in the elderly: preventive techniques.

Predictive value is a critical consideration when one is deciding whether to order a specific test on an individual patient in whom the disease status is unknown. Positive tests are most useful when prevalence is high; negative tests are most useful when prevalence is low. Falls from bed, comprising 36% of these accidents, chiefly occurred in the evening or at night, often while the patient was attempting to get in or out of bed, or was sleeping. All these accidents occurred with the bedrails up.