Table of
Contents
Separate Measurement of FN and FP Correlations Between 2
Diagnostic Tests Permits Clinical Probability Revision Robert M. Hamm, PhD
Correlated Signs, Symptoms, or Test Results
Example: "Test Characteristics" of Signs of
Appendicitis. (Wagner, JAMA, 1997, 278:819)
Clinical use of correlated symptoms
Bayes' Theorem for Appendicitis
What if all appendicitis signs were known?
What if the signs are not independent?
Bayesian approaches
Multiple Logistic Regression (Steyerberg,
Eijkemans, and Hilden,
1998; Knottnerus, 1992)
Heuristic Groupings
Tables and Correlations
Phi Correlation (both variables dichotomous)
What correlation?
Table Approach - Input data, assuming conditional
independence
2 by 2 by 2 Table, assuming conditional independence
Posterior Probabilities, assuming conditional independence
Conditional Sensitivity and Specificity, assuming
conditional dependence with r(FNs) = .40, r(FPs) = .40
Posterior Probabilities, assuming conditional dependence
with r(FNs) = .40, r(FPs)
= .40
Examples: Data from clinical studies
Alzheimer's: post test probabilities, all combinations of
two test results.
Post test probabilities with and without conditional
dependence.
Example: PSA and DRE for Prostate
Cancer (Cooner, 1990)
Prostate Cancer
Example: Coronary Artery Stenosis (Sackett's
text)
Coronary Artery Stenosis, continued
Conclusions
Future Research: Psychological
Future Research: Statistical
|