Caveat Medicus: It's Time to Re-Think Stratification, You May Not Be Helping.

Background: The focus of the present Letter is on the large and seemingly fertile body of work captured under the umbrella of 'patient stratification'.

Objectives: I identify and explain a fundamental methodological flaw underlying the manner in which the development of an increasingly large number of new stratification strategies is approached.

Design: I show an inherent conflict between the assumptions made, and the very purpose of stratification and its application in practice.

Methods: I analyse the methodological underpinnings of stratification as presently done and draw parallels with conceptually similarly flawed precedents which are now widely recognized.

Results: The highlighted flaw is shown to undermine the overarching ultimate goal of improved patient outcomes by undue fixation on an ill-founded proxy.

Conclusion: I issue a call for a re-think of the problem and the processes leading to the adoption of new stratification strategies in the clinic.