MRMCsamplesize (version 1.0.0)

sampleSize_Standalone: Estimate sample sizes for standalone studies with sensitivity or AUC as endpoint

Description

sampleSize_MRMC This function returns number of cases required for a standalone study for endpoints of sensitivity and AUC.

Usage

sampleSize_Standalone(
  endpoint = "auc",
  theta,
  precision,
  R = 1,
  power = 0.8,
  alpha = 0.05,
  var_auc = "obuchowski",
  corr = FALSE,
  ICC = NULL,
  s = NULL
)

Value

A named list

• SampleSizeResults - A list containing the sample size results.

Arguments

endpoint

Character string to inform what is the endpoint (Figure-Of-Merit - FOM) of the standalone study. Values can be either auc or sensitivity.

theta

Expected average value of the FOM Must be a value between 0 and 1.

precision

Required precision of the point estimate of FOM. This is equivalent to half-width of the confidence interval. Must be a numeric value between 0 and 1.

R

Ratio of non-diseased cases to diseased cases. Defaults to 1.

power

Power to detect delta given all other assumptions. Default value is 0.8 corresponding to 80 percent power.

alpha

The type I error rate. Default value is 0.05 corresponding to 5 percent type I error (significance level).

var_auc

Variance estimation method when endpoint is auc. Defaults to the string obuchowski. If value is changed to blume, then method proposed by Blume (2009) will be used to estimate the variance.

corr

Logical value indicating if ICC (intra-cluster correlation) has to be adjusted (TRUE) or not (FALSE). Defaults to FALSE.

ICC

A numerical value between 0 and 1 indicating the expected ICC if corr is TRUE.

s

Average number of lesions in diseased cases. This must be a numeric value greater than or equal to 1.

Author

Dennis Robert

Details

When corr = FALSE, the nUnits_i in SampleSizeResults is the number of diseased cases. The number of total cases (nTotal) required will depend on the the ratio R specified. When corr = TRUE, the anticipated correlation between units within the same diseased cases are adjusted and the nUnits_i in SampleSizeResults list is the number of units in diseased cases assuming independence. The number of diseased cases required in this scenario will be given by nCases_c. Again, nTotal will depend on the R specified.

References

• Flahault A, Cadilhac M, Thomas G. Sample size calculation should be performed for design accuracy in diagnostic test studies. J Clin Epidemiol. 2005 Aug;58(8):859-62. doi: 10.1016/j.jclinepi.2004.12.009. PMID: 16018921.

• Zhou, X.-H., Obuchowski, N.A. and McClish, D.K. (2011). Sample Size Calculations. In Statistical Methods in Diagnostic Medicine (eds X.-H. Zhou, N.A. Obuchowski and D.K. McClish). https://doi.org/10.1002/9780470906514.ch6

Examples

library("MRMCsamplesize")
result1 <- sampleSize_Standalone(endpoint = "auc", theta = 0.9, precision = 0.05,
                                 R = 1, corr = TRUE, ICC = 0.5, s = 1.25)
result2 <- sampleSize_Standalone(endpoint = "Se", theta = 0.8, precision = 0.05, R = 1)