When I teach undergraduates what kind of different research questions one might want to answer, I sometimes use the mental image of a patient in the doctor’s office. The questions that are asked can be roughly categorized in “What is wrong with me?”, “How did I get it?”, “What will happen from now on?”, and “What can we do about it?”. Students with a quick mind can recognize the concepts of diagnosis, etiology, prognosis, and treatment hidden in these questions. I usually treat these as quite separate questions, and that for each category different study designs and statistical techniques are preferable.
But that changed after I prepared for the PhD defense of SB. As a member of the “opposite”, I was tasked to examine the PhD candidate on her knowledge and her work presented in her thesis. Titled “The early identification of patients with an unfavorable prognosis”, this thesis focussed on the theme of whether treatment response could be incorporated in prediction models in order to improve the prediction of outcome. I think this is an interesting concept and potentially heavily underutilized and at least heavily understudied.
SB started out by showing that in psychiatry the majority of care is consumed by a minority of patients, thereby conceptually proving the need of identifying patients with an unfavorable outcome. The next chapters test whether adding information on treatment response for three different diseases: depression, asthma and high blood pressure.
Being the last of the opposition committee to examine the candidate, I was able to ask more about the methodological details (presence of co-linearity, the calibration/validation of the final models, the use of complete case analyses, etc). These introductory questions led us to the broader question that focused on her approach to include information about treatment response. SB consistently used the delta of two absolute measurements as an indicator of treatment response, and I asked whether that could be replaced or even complimented by using the delta in the variation of certain measurements. The bottom line is of course is that we don’t know, but that is also not the objective of a Dutch PhD ceremony. The objective is to start a conversation during which the candidate can show that he or she masters the material and is ready to become an independent researcher. And that is what SB did, congratulations!
So what did I learn from all this? Perhaps using the four categories of research questions is too restrictive and that sometimes, by combining the ideas and concepts from questions on treatment and prediction we can actually improve the care we can better distribute the care we can provide for all our patients.