Differences in Diagnostic Likelihood Ratios

Description

Performs a test for differences in (positive and negative) diagnostic likelihood ratios (DLRs) of two binary diagnostic tests in a paired study using a regression model approach proposed by Gu and Pepe (2009).

Usage

1
dlr.regtest(tab, alpha)

Arguments

tab

An object of class tab.paired.

alpha

Significance level alpha for 100(1-alpha)%-confidence intervals, the default is 0.05.

Details

The null hypothesis rDLR = DLR of Test 1 / DLR of Test 2 = 1 is tested with respect to both positive and negative DLRs of the two diagnostic tests.

This function calls DLR, a general implementation of the method proposed by Gu and Pepe (2009).

Value

A list containing

pdlr

A list with test1 (the positive DLR of test 1), test2 (the positive DLR of test 2), ratio (the ratio of positive DLRs, computed as test1/test2, se.log (the standard error of the logarithm of ratio), the test.statistic and the corresponding p.value.

ndlr

A list with test1 (the negative DLR of test 1), test2 (the negative DLR of test 2), ratio (the ratio of negative DLRs, computed as test1/test2, se.log (the standard error of the logarithm of ratio), the test.statistic and the corresponding p.value.

alpha

The significance level alpha used to compute 100(1-alpha)%-confidence intervals for the ratio of positive and negative DLRs, the default is 0.05.

method

The name of the method used to compare the positive and negative DLRs, here “diagnostic likelihood regression model (regtest)”.

References

Gu, W. and Pepe, M. S. (2009). Estimating the capacity for improvement in risk prediction with a marker. Biostatistics, 10(1):172-86.

See Also

DLR

Examples

1
2
3
4
5
6
data(Paired1) # Hypothetical study data
ptab <- tab.paired(d=d, y1=y1, y2=y2, data=Paired1)
ptab
dlr.results <- dlr.regtest(ptab)
str(dlr.results)
dlr.results