Linnet K
Laboratory of Clinical Biochemistry, Psychiatric University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark. Fax 45 86170778, USA.
Clin Chem. 1999 Jun;45(6 Pt 1):882-94.
In method comparison studies, it is of importance to assure that the presence of a difference of medical importance is detected. For a given difference, the necessary number of samples depends on the range of values and the analytical standard deviations of the methods involved. For typical examples, the present study evaluates the statistical power of least-squares and Deming regression analyses applied to the method comparison data.
Theoretical calculations and simulations were used to consider the statistical power for detection of slope deviations from unity and intercept deviations from zero. For situations with proportional analytical standard deviations, weighted forms of regression analysis were evaluated.
In general, sample sizes of 40-100 samples conventionally used in method comparison studies often must be reconsidered. A main factor is the range of values, which should be as wide as possible for the given analyte. For a range ratio (maximum value divided by minimum value) of 2, 544 samples are required to detect one standardized slope deviation; the number of required samples decreases to 64 at a range ratio of 10 (proportional analytical error). For electrolytes having very narrow ranges of values, very large sample sizes usually are necessary. In case of proportional analytical error, application of a weighted approach is important to assure an efficient analysis; e.g., for a range ratio of 10, the weighted approach reduces the requirement of samples by >50%.
Estimation of the necessary sample size for a method comparison study assures a valid result; either no difference is found or the existence of a relevant difference is confirmed.
在方法比较研究中，确保检测到具有医学重要性的差异至关重要。对于给定的差异，所需的样本数量取决于所涉及方法的数值范围和分析标准差。对于典型示例，本研究评估了应用于方法比较数据的最小二乘法和戴明回归分析的统计功效。
使用理论计算和模拟来考虑检测斜率与1的偏差以及截距与0的偏差的统计功效。对于具有成比例分析标准差的情况，评估了加权形式的回归分析。
一般来说，方法比较研究中通常使用的40 - 100个样本的样本量常常需要重新考虑。一个主要因素是数值范围，对于给定的分析物，该范围应尽可能宽。对于范围比（最大值除以最小值）为2的情况，需要544个样本才能检测到一个标准化斜率偏差；当范围比为10（成比例分析误差）时，所需样本数量降至64个。对于数值范围非常窄的电解质，通常需要非常大的样本量。在成比例分析误差的情况下，应用加权方法对于确保有效分析很重要；例如，对于范围比为10的情况，加权方法可将样本需求减少超过50%。
估计方法比较研究所需的样本量可确保获得有效的结果；要么未发现差异，要么确认存在相关差异。
