Phillips W R, Thompson D J
N Z Med J. 1981 Dec 23;94(698):462-4.
Multi-channel automatic analysers generate unexpected abnormal test results impacting medical economics, policy and practice. Critics caution that many such abnormal results should be expected due simply to the statistical definition of normal limits. With a test battery of n channels the probability p that a healthy individual will be within limits on all tests, each with probability s, is usually predicted p = sn. In most clinical situations, however, the assumptions upon which this formula rests are not met and it overestimates the occurrence of abnormal results. In three screening programmes involving blood chemistry batteries on 769 patients the formula gave overestimates (p less than 0.001) of the percentage of individuals with at least one abnormal result. For a battery of eight tests 33.7 percent of patients were predicted to have abnormal results but only 20.6 percent were observed, with 14 tests 51.2 percent were predicted and only 37.1 percent observed, for 17 tests 58 percent were predicted and only 33.3 percent observed. Clinical judgment, not misapplied probability theory, should guide the physician's strategy in evaluating abnormal test results.
多通道自动分析仪会产生意想不到的异常检测结果，这对医学经济、政策及实践均产生影响。批评者警告称，仅由于正常范围的统计定义，就应预料到许多此类异常结果。对于一个有(n)个通道的检测组合，健康个体在所有检测中都处于正常范围的概率(p)（每个检测的正常概率为(s)）通常预计为(p = s^n)。然而，在大多数临床情况下，该公式所基于的假设并不成立，且它高估了异常结果的发生率。在三项涉及对769名患者进行血液化学检测组合的筛查项目中，该公式高估了（(p\lt0.001)）至少有一项异常结果的个体百分比。对于一个包含八项检测的组合，预计有33.7%的患者会有异常结果，但实际观察到的只有20.6%；对于14项检测，预计有51.2%，实际观察到的只有37.1%；对于17项检测，预计有58%，实际观察到的只有33.3%。在评估异常检测结果时，应指导医生策略的是临床判断，而非误用概率理论。
