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Table 3 Two-year service utilization and cost difference in differences from baseline relative to control arm

From: Cost-effectiveness analysis of a cluster-randomized, culturally tailored, community health worker home-visiting diabetes intervention versus standard care in American Samoa

  Utilization DiD Cost DiD
Intervention direct
 Intervention (use) 1.00 $677.43
Medical direct
 ED (visits) − 0.61 − $83.77
 Ambulatory (visits) − 0.18 − $38.38
 Hospitalizations (inpatient days) − 0.14 $19.29
 Surgery − 0.10 − $12.92
Indirect patient time
 Intervention indirect (hours) 10.03 $47.76
 Medical indirect (hours) − 3.74 − $15.15
Total   $594.27
  1. Note: Utilization difference in differences (DiD): mean differences in pre-post service use of community health worker (CHW) arm to control arm. Positive numbers are service increases in the CHW arm. Total differences are divided by follow-up person-years (p-y) in each intervention arm [CHW 100 p-y, control 163 p-y [14]]. Cost difference in differences: the difference in cost per patient per year, derived by multiplying utilization differences by the cost of each utilization output (not displayed). DiD in costs from the baseline period (− 12 to 0 months) for each patient relative to control across the intervention time period (0 to 12 months). All costs in 2012 USD ($). See Additional file 1: Table S1 for further medical cost breakdown. Intervention direct: mean difference is participation in the intervention: since all intervention arm patients received (CHW) home visits, the mean difference is 1. Cost is per participation in the program based on staffing, equipment usage, donated space, and consumables. Medical direct: four broad categories. Ambulatory visits are summed across internal medicine clinic, primary care clinic, community health center, ophthalmology, surgical clinic, mental health clinic, and ENT. Hospitalizations are summed across inpatient days in the medical ward, surgical ward, and ICU. Please see Additional file 1: Table S1 for further breakdown. Indirect patient time: “intervention indirect” denotes average time spent by the patient during home visits. “Medical indirect” includes time spent during ED and ambulatory visits (estimated at 1/2 h) and during hospital inpatient days (estimated at 24 h). Costs calculated at the minimum wage of $4.76 per hour plus time-and-a-half if over 8 h (Department of Labor). Total: net total difference in costs per patient per year summed across all cost differences. This is the incremental cost difference