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. 2011 Nov;197(5):W821-8.
doi: 10.2214/AJR.11.6764.

Sample size tables for computer-aided detection studies

Nancy A Obuchowski  1 , Stephen L Hillis
Affiliations

Sample size tables for computer-aided detection studies

Nancy A Obuchowski et al. AJR Am J Roentgenol. 2011 Nov.

Abstract

Objective: Calculating the sample size for a multireader, multicase study of readers' diagnostic accuracy is complicated. Studies in which patients can have multiple findings, as is common in many computer-aided detection (CAD) studies, are particularly challenging to design.

Materials and methods: We modified existing methods for sample size estimation for multireader, multicase studies to accommodate multiple findings on the same case. We use data from two large multireader, multicase CAD studies as ballpark estimates of parameter values.

Results: Sample size tables are presented to provide an estimate of the number of patients and readers required for a multireader, multicase study with multiple findings per case; these estimates may be conservative for many CAD studies. Two figures can be used to adjust the number of readers when there is some data on the between-reader variability.

Conclusion: The sample size tables are useful in determining whether a proposed study is feasible with the available resources; however, it is important that investigators compute sample size for their particular study using any available pilot data.

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Figures

Fig. 1
Fig. 1
Estimated percentage reduction in required reader sample size as function of variance of interaction between reader and test for studies using sensitivity as endpoint. Two points represent maximum (0.0014) and median (0.000704) values of variance observed over two studies described in text.
Fig. 2
Fig. 2
Estimated percentage reduction in required reader sample size as function of variance of interaction between reader and test for studies using area of receiver operating characteristic curve as endpoint. Two points represent maximum (0.0014) and median (0.000145) values of variance observed over two studies described in text.
See this image and copyright information in PMC

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