Outcome measure: NSI incidence

The incident NSIs among police officers exposed to needles/syringes during the pretraining and post-training period, respectively, was the study’s initial primary outcome of interest. To determine the incident NSIs for the pretraining period, in the baseline survey study participants who indicated having contact with needles/syringes were asked to report the number of NSIs sustained since the beginning of the Escudo training (ie, 28 February 2015) and the current date (ie, date of their pretraining survey). For those who sustained at least one NSI during the pretraining period, the time at risk was considered to be the time between the beginning of Escudo and the approximate date provided for the first NSI. If a date was not provided, then the event was assumed to have taken place mid-interval and the time at risk was calculated, accordingly. For those who did not sustain an NSI during the pretraining period, the time at risk was considered to be the length of their entire pretraining period (ie, time between the beginning of Escudo and the date they took the pretraining survey). Similarly, to determine the incident NSIs for the post-training period, at each follow-up visit (ie, 3, 6, 12, 18 and 24 months) study participants who indicated contact with needles, were asked to report the number of NSIs sustained since the previous visit. On the 3-month survey only, we also prompted participants for a repeat measure of their NSI experience pretraining to assess repeat test reliability. For participants who sustained at least one NSI during the post-training period, the time at risk was considered to be the time between the date of their pretraining survey and the date of their first NSI, which was assumed to have occurred at the midpoint between their last visit without an NSI and their first visit with an NSI. For participants who did not sustain an NSI during this period, the time at risk was considered to be the length of their entire post-training period (ie, between the date of their pretraining survey and the date of their last post-training survey). Notably, formative research within this cohort suggested reliability and measurement challenges with using self-reported NSI data as the primary outcome, including concerning levels of discrepancy between the test–retest measure of baseline NSI experience. Also, we found that prior to the training, knowledge of NSI and reporting procedures was low (online supplemental table S2).

bmjopen-2020-041629supp002.pdf