# dlr.regtest: Differences in Diagnostic Likelihood Ratios In DTComPair: Comparison of Binary Diagnostic Tests in a Paired Study Design

## 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.

`DLR`
 ```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 ```