Queraltó J M, Boyd J C, Harris E K
Servei de Bioquimica, Hospital de la Santa Creu I Sant Pau, Barcelona, Spain.
Clin Chem. 1993 Jul;39(7):1398-403.
Reference change values (sometimes called critical differences) indicate statistically important changes between test values obtained on two occasions. They are commonly computed from the median (or mean) within-subject variance observed in repeated test measurements on a number of subjects. With this computational approach, all observed within-subject variances are assumed to be estimates of a constant true variance, the same for all individuals. Moreover, any possible correlation between successive values is almost always ignored. This simplified methodology differs from the method originally proposed for computing reference change values, which accounts for variability in true variances and for serial correlation. From data obtained from repeated measurements over 2 to 5 years in 72 physically healthy subjects, we computed and compared reference change values in 18 serum analytes, using the simplified method and the originally proposed procedure. Although the original method is more complicated and requires a computer program, we believe that it produces more-reliable reference change values than those obtained by the simplified approach. The former are generally larger, but remain sensitive to clinically important changes in the individual.
参考变化值（有时称为临界差异）表明两次检测所得检测值之间具有统计学意义的变化。它们通常根据对若干受试者进行重复检测时观察到的受试者内中位数（或均值）方差来计算。采用这种计算方法时，所有观察到的受试者内方差都被假定为一个恒定真实方差的估计值，对所有个体而言都是相同的。此外，连续值之间的任何可能相关性几乎总是被忽略。这种简化方法不同于最初提出的计算参考变化值的方法，后者考虑了真实方差的变异性和序列相关性。根据72名身体健康的受试者在2至5年期间重复测量获得的数据，我们使用简化方法和最初提出的程序计算并比较了18种血清分析物的参考变化值。尽管原始方法更为复杂且需要计算机程序，但我们认为它所产生的参考变化值比简化方法获得的参考变化值更可靠。前者通常更大，但对个体临床重要变化仍保持敏感。
