Evaluation of diagnostic tests for diseases in pregnancy: some statistical issues
A diagnostic test is used typically because it is cheaper, quicker or less invasive than the reference standard, but may not be as reliable. Diagnostic tests are evaluated against a reference standard (sometimes called "Gold Standard"), regarded as completely accurate. Commands diagt and diagti have been developed to evaluate binary tests, and provide all the standard measures of performance (including sensitivity, specificity, likelihood ratios, and predictive values, with appropriate confidence intervals. A "prevalence" option adjusts for different case-mix, and evaluates the test result for a particular patient with known pre-test risk. The use of ROC curves for ordered categorical and continuous data will be considered, in particular the determining of a suitable cut-off value. Where the distribution of a continuous measure can be adequately modelled, the likelihood ratio can be used to determine the absolute risk of an individual patient. Appropriate Stata commands for these analyses will be demonstrated.
Year of publication: |
2004-06-30
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Authors: | Seed, Paul T. |
Institutions: | Stata User Group |
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