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October 18, 2004

Outcomes affect expert testimony

It's been long understood that medical malpractice is more likely to be found where the injury suffered by a plaintiff is severe; in other words, juries are judging the end result, rather than whether the defendant met the quality of care. Amazingly, one study finds that expert witnesses often suffer from the same bias.

In 1991, the Closed Claims Project database was used to explore the possibility that the opinions of experts may be influenced by the severity of patient injury. The specific goal was to determine whether severe injuries were more likely than minor injuries to predispose medical experts toward harsh judgments about the appropriateness of anesthesia care.

To study this question in a rigorous manner, 112 practicing anesthesiologists were recruited to judge the appropriateness of anesthesia care using 21 case summaries selected from the Closed Claims Project database. About one-half of the cases had temporary injuries and one-half had permanent injuries or death. For each case, a matching but "fictitious" version was created that was identical in every detail to the original case except that a plausible outcome of opposite severity was substituted. The original and fictitious cases were divided randomly into two sets and assigned to the volunteer reviewers, who were unaware of the intent of the study. The reviewers were asked to independently rate the appropriateness of anesthesia care in each case, based upon the conventional yardstick of reasonable and prudent practice applicable to the year the event occurred.

How did the ratings of appropriateness of care differ between the original and fictitious cases, which differed only in the severity of injury? The proportion of ratings for appropriate care decreased by 31 percentage points (from 67 percent to 36 percent) when the case outcome was changed from a temporary injury to a permanent injury. Conversely, the proportion of ratings for less-than-appropriate care increased by 28 percentage points (from 28 percent to 56 percent) when the case outcome was changed from temporary to permanent injury. These findings indicate that the severity of injury can have a substantial impact on a reviewer's assessment of the appropriateness of care.

(Caplan RA, Posner KL: The expert witness: Insights from the Closed Claims Project. ASA Newsletter 61(6):9-10, 1997; Caplan RA, Posner K, Cheney FW: Effect of outcome on physician judgments of appropriateness of care. JAMA 265:1957-1960, 1991).

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