Differential Intervention Cost
The differential intervention cost (iBASIS-VIPP compared with TAU) incorporated all child development–related services delivered during the 6-month intervention period. Data inputs were derived from trial records.The iBASIS-VIPP intervention is a manualized program with a defined number of sessions delivered by suitably qualified and trained staff in participants’ homes. The intervention cost for delivering iBASIS-VIPP included the following: (1) therapy costs, (2) direct travel costs, (3) therapy-related administration costs, and (4) training and supervision costs. First, therapy costs were calculated as the product of the number of sessions delivered by the therapist (introductory, core, booster) and mean hours per session delivered in participants’ homes, plus other therapy-related activities (eg, time to review video material), administrative time (eg, appointment scheduling), and published clinician hourly rates