Cohort Profile: Baseline Characteristics of Veterans from Improving Veteran Access to Integrated Management of Back Pain (AIM-Back) - an Embedded Pragmatic, Cluster Randomized Trial in the United States.

Purpose: AIM-Back is an embedded pragmatic clinical trial (ePCT) with cluster randomization designed to increase access and compare the effectiveness of two different non-pharmacological care pathways for low back pain (LBP) delivered within the Veteran Administration Health Care System (VAHCS). This manuscript describes baseline characteristics of AIM-Back participants as well as the representativeness of those referred to the AIM-Back program by sex, age, race, and ethnicity, relative to Veterans with low back pain at participating clinics. Participants: To be eligible for AIM-Back, Veterans were referred to the randomized pathway at their clinic by trained primary care providers (Referral cohort). Veterans from the Referral cohort that participated in the study included: 1) an Electronic Health Record (EHR) sample of Veterans enrolled in the program (i.e., attended initial AIM-Back visit with no consent required) and a Survey sample of Veterans that were consented for further study. Descriptive statistics for age, race, ethnicity, sex, high-impact chronic pain (HICP), a comorbidity measure, post-traumatic stress diagnosis (PTSD) and opioid exposure were reported for the Referral cohort and by sample; mean baseline PROMIS pain interference, physical function and sleep disturbance scores were reported by sample. Additional measures of pain, mental health and social risk were reported on the Survey sample. Participation to prevalence ratios (PPRs) were calculated for sex, age, race, and ethnicity by clinic to describe representativeness of the Referral cohort. Findings to Date: Across 17 randomized primary care clinics, the Referral cohort included 2767 unique Veterans with n=1817 in the EHR sample, n=996 in the Survey sample and n=799 of the EHR sample (44%) were also in the Survey sample. High rates of HICP were observed in the EHR and Survey samples (>59%). Mean scores (SD) based on self-reported PROMIS Pain Interference (63.2 (6.8), 63.1 (6.6)) and PROMIS Physical Function (37.1 (5.3), 38.1 (5.8)) indicated moderate impairment in the EHR sample and Survey sample respectively. Approximately 10% of the EHR sample had documented opioid use in the year leading up to the AIM-Back referral. At most clinics, older Veterans (>=65 years) were underrepresented in the Referral cohort compared to those with LBP visits at clinics (PPRs < 0.8). Future Plans: The AIM-Back trial will conduct analysis to examine the comparative effectiveness of the two care pathways and identify individual characteristics that may improve responses to each pathway. The trial is expected to complete 12-month follow-up data collection by December 2024, with subsequent analyses and publications providing insights into optimizing non-pharmacological care for Veterans with LBP. Trial Registration: NCT04411420 (clinicaltrials.gov).