Statistical methods for evidence-based medicine: the diagnostic test. Part II.

Part II of this work addresses the use of likelihood ratios for the calculation of a positive predictive value (PPV) and a negative predictive value (NPV) for patient diagnosis. These two values are the most useful indices in the application of a diagnostic test in order to make a diagnosis for a patient. Furthermore, the relevance of sample size is also addressed by providing background theory and pertinent tables. These basic topics for assessing the validity of a diagnostic test and for performing appropriate and valid case vs control studies are explained in a simple way for a clinical audience with a working example.