Assignment task: A U.S.-based cohort study began in 2017 to assess the effect of oral opioid prescribing patterns after surgery on the incidence of misuse (Brat et al, 2018). The investigators used a healthcare management organization database to obtain diagnostic codes for misuse occurring between 2008 and 2016. Data on postsurgical opioid use was determined using a linked prescription dispensation database that tracks the date each prescription is filled and classified as ≥1 refill or no refills.
a. Over the follow-up period in this study, postsurgical patients with ≥1 opioid refill experienced 676 cases of misuse during 230,765 person-years of observation. Postsurgical patients who did not refill their opioid prescription experienced 1,678 cases of misuse during 1,156,863 person-years of observation. Calculate the attributable rate for the effect of having ≥1 opioid refill on incidence of misuse among U.S. postsurgical patients, assuming a causal relationship between the exposure and the outcome.