# Positive and negative likelihood ratios

Slide ten of these pdf slides indicates rules of thumb for assessing positive and negative likelihood ratios to evaluate them to assess discrimination of the model.

where

Positive likelihood ratio = Sensitivity / (1 - Specificity)

Negative likelihood ratio = (1 - Sensitivity) / Specificity

The slides also briefly mention Hierarchical ROC curves which are useful for plotting curves combining within and between study variances from studies in meta-analyses.

Reference

Jaeschke R, Guyatt, GH and Saclett DL (1994) Users guides to the medical literature. III. How to use an article abotu a diagnostic test. B. What are the results and will they help me in caring for my patients? The Evidence-Based medicine Working Group. *Journal of the American medical Association*, **271(9)**, 703-707.