Authors' Reply to 'Pyogenic Liver Abscess and Risk of Acute Pancreatitis'.

Abstract

Dear Dr. Shen, We sincerely thank you for your interest in our study, which was recently published in the Journal of Epidemiology.1 First, we agree that, in the presence of non-proportional hazards, presenting an average hazard ratio (HR) over the entire follow-up period might not be informative because the magnitude of effect changes over time. However, a methodology report has shown that period-specific HRs (ie, HRs estimated in time-partitioned periods) may have built-in selection bias.2 Therefore, instead of time-partitioned estimations, we presented a series of average HRs with increasingly longer follow-up time, with findings showing that the elevated risk of acute pancreatitis associated with pyogenic liver abscess steadily decreased over time and that the association persisted for 5 years (Table 2 of our paper). Second, we agree that the strength of interaction effects of pyogenic liver abscess and comorbidities on risk of acute pancreatitis (Table 3 of our paper) may differ among time-partitioned periods. If possible, we will analyze this effect for each time-partitioned period in further research. We appreciate your helpful comments.