Fig. 3.

Interpretation of a possible spurious association between use of DPP4i and better outcomes of COVID-19. Specific clinical characteristics are typically associated with the probability of receiving a DPP4i. In addition, having attended diabetes clinics before COVID-19 or being seen by a diabetes specialist during hospitalization increases the likelihood of receiving a DPP4i. In both cases, the observed outcome can be confounded by different clinical characteristics or by indirect effect of diabetes specialist care. Thus, the direct link between use of DPP4i and lower mortality is highlighted with a question mark