I hear the terms predictive and prognostic factors getting thrown around a lot (usually in the context of biostatistics) and I am very unsure of what the difference between them is. Could someone please give a definition of each, an example of the two, and ultimately how they are different from each other?
This is an excellent question because the two are being terribly misused in personalized medicine and biomarker studies. The correct definition of the two, at least when it comes to data, is the same. Here is how the terms are being misused in personalized/precision medicine: prognostic is taken to mean predictive and predictive is taken to mean interaction, i.e., the ability to predict differences in treatment effectiveness over values of patient covariates. The correct terminology should be: predictive/prognostic for ability to forecast outcomes, and modeling interactions/differential treatment effect for the other.