Using all available longitudinal EHR AUDIT-C measurements, we calculated two AUDIT-C metrics: the age-adjusted mean AUDIT-C value and a four-level trajectory of AUDIT-C scores for each participant. As previously reported (8), using the SAS 9.2 procedure, TRAJ (20), we estimated four-level longitudinal statistical trajectories of AUDIT-C (infrequent, lower risk, potentially high risk, and consistently high risk), using age as the time scale to account for decreasing alcohol use with age. The procedure calculates each participant’s probability of belonging to each trajectory and assigns him or her to the trajectory with the highest probability of membership. Age was used as the time scale, thus each individual could only contribute one AUDIT-C score for each age (i.e., year). Participants’ modal AUDIT-C scores were used for each age at which they received the AUDIT-C assessment. The analysis used a zero-inflated Poisson model (20). The median probability of membership calculated for all four groups was >90%. Trajectory analysis allows for missing longitudinal data, thus no individuals or observations were excluded due to missingness.
