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May 30, 1977

Decision Analysis

Author Affiliations

The Rand Corporation Santa Monica, Calif

JAMA. 1977;237(22):2380. doi:10.1001/jama.1977.03270490020007

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To the Editor.—  The article entitled "Clinical Decision Analysis: The Hazard of Using Additional Data" (236:1259, 1976) suggests that costless, risk-free information can make patient care worse rather than better. In fact, properly used free information can never make any decision worse—the decision-maker can always ignore it (Raiffa, Decision Analysis, 1968). The examples given in the article actually make two different but important common-sense points. First, even if a test result favors a certain diagnosis, one shouldn't act as if the diagnosis is certain. Second, a test has diagnostic value only when some conceivable result of that test will alter treatment. In both examples in the article, the test is not discriminating enough to alter treatment if the results are properly weighed.For example, in the case of bronchogenic cancer, 20% of patients are assumed to have undetected metastases, and a liver scan is assumed to have a probability of