"A tremendous dataset — very powerful … and to be able to both develop and validate a prediction model was very impressive." That's how PTJ Editor-in-Chief Alan Jette, PT, PhD, FAPTA, characterizes the latest research of Gerard Brennan, PT, PhD, FAPTA, on predicting clinical improvement in low back pain using the Modified Low Back Pain Disability Questionnaire. The study looked at 63,000 patients with low back pain and 15,000 patients in the validation dataset. What led Brennan to pursue this line of investigation?