Diagnostic accuracy

When conducting a test there are two main factors:

a cutoff value indicating whether an individual can be classified as positive (above/below the cutoff) or negative (below/above the cutoff)– a reference

(“gold”) standard which will indicate to the best of our knowledge whether the same individual is indeed ill or healthy

The pretest probability is especially useful for four things

interpreting the results of a diagnostic test

selecting one or more diagnostic tests

choosing whether to start therapy: a) without further testing (treatment threshold) b) while awaiting further testing

deciding whether it’s worth testing at all (test threshold)

Likelihood ratio (LR)

provides a numerical measure of the effect of a result on probability

A clinical prediction rule (CPR)

is a guideline in which the best combination of medical signs, symptoms, and other clinical findings in predicting the probability of a specific disease or outcome are determined