Bachmann Lucas M, Puhan Milo A, ter Riet Gerben, Bossuyt Patrick M
Division of Epidemiology and Biostatistics, Department of Social and Preventive Medicine, University of Bern, Switzerland.
BMJ. 2006 May 13;332(7550):1127-9. doi: 10.1136/bmj.38793.637789.2F. Epub 2006 Apr 20.
To determine sample sizes in studies on diagnostic accuracy and the proportion of studies that report calculations of sample size.
Literature survey.
All issues of eight leading journals published in 2002.
Sample sizes, number of subgroup analyses, and how often studies reported calculations of sample size were extracted.
43 of 8999 articles were non-screening studies on diagnostic accuracy. The median sample size was 118 (interquartile range 71-350) and the median prevalence of the target condition was 43% (27-61%). The median number of patients with the target condition--needed to calculate a test's sensitivity--was 49 (28-91). The median number of patients without the target condition--needed to determine a test's specificity--was 76 (27-209). Two of the 43 studies (5%) reported a priori calculations of sample size. Twenty articles (47%) reported results for patient subgroups. The number of subgroups ranged from two to 19 (median four). No studies reported that sample size was calculated on the basis of preplanned analyses of subgroups.
Few studies on diagnostic accuracy report considerations of sample size. The number of participants in most studies on diagnostic accuracy is probably too small to analyse variability of measures of accuracy across patient subgroups.
确定诊断准确性研究中的样本量以及报告样本量计算的研究比例。
文献调查。
2002年出版的8种主要期刊的所有期次。
提取样本量、亚组分析数量以及研究报告样本量计算的频率。
8999篇文章中有43篇为诊断准确性方面的非筛查研究。样本量中位数为118（四分位间距71 - 350），目标疾病的患病率中位数为43%（27 - 61%）。计算一项检测敏感度所需的目标疾病患者数量中位数为49（28 - 91）。确定一项检测特异度所需的非目标疾病患者数量中位数为76（27 - 209）。43项研究中有2项（5%）报告了样本量的预先计算。20篇文章（47%）报告了患者亚组的结果。亚组数量从2个到19个不等（中位数为4个）。没有研究报告样本量是根据亚组的预先计划分析计算得出的。
很少有诊断准确性研究报告对样本量的考量。大多数诊断准确性研究中的参与者数量可能太少，无法分析不同患者亚组中准确性测量指标的变异性。
