The online version of this article (doi:10.1186/1471-2288-14-67) contains supplementary material, which is available to authorized users.
The authors declare that they have no competing interests.
The absence of a gold standard, i.e., a diagnostic reference standard having perfect sensitivity and specificity, is a common problem in clinical practice and in diagnostic research studies. There is a need for methods to estimate the incremental value of a new, imperfect test in this context.
We use a Bayesian approach to estimate the probability of the unknown disease status via a latent class model and extend two commonly-used measures of incremental value based on predictive values [difference in the area under the ROC curve (AUC) and integrated discrimination improvement (IDI)] to the context where no gold standard exists. The methods are illustrated using simulated data and applied to the problem of estimating the incremental value of a novel interferon-gamma release assay (IGRA) over the tuberculin skin test (TST) for latent tuberculosis (TB) screening. We also show how to estimate the incremental value of IGRAs when decisions are based on observed test results rather than predictive values.
We showed that the incremental value is greatest when both sensitivity and specificity of the new test are better and that conditional dependence between the tests reduces the incremental value. The incremental value of the IGRA depends on the sensitivity and specificity of the TST, as well as the prevalence of latent TB, and may thus vary in different populations.
Even in the absence of a gold standard, incremental value statistics may be estimated and can aid decisions about the practical value of a new diagnostic test.
Additional file 1: Table S1: WinBUGS program for estimating the latent class model, IDI and AUCdiff statistics. (DOCX 19 KB)
Additional file 2: Table S2: Priors for T2 in simulation study of the conditional dependence model. (DOCX 15 KB)
Additional file 3: Table S3: Average coverage, average bias and average length of 95% posterior credible intervals of AUCdiff and IDI statistics resulting from fitting conditional independence latent class model to 1000 simulated datasets. (DOCX 16 KB)
Additional file 4: Table S4: Average coverage, average bias and average length of 95% posterior credible intervals of AUCdiff and IDI statistics resulting from fitting conditional dependence latent class model to 1000 simulated datasets. (DOCX 17 KB)
Additional file 5: Table S5: Median posterior estimates and 95% credible intervals of parameters for latent class model and AUCdiff and IDI statistics using data from applied examples when using wider prior distributions. (DOCX 18 KB)
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- A Bayesian framework for estimating the incremental value of a diagnostic test in the absence of a gold standard
Daphne I Ling
- BioMed Central
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