Smalley 1995

Methods	Controlled ITS using segmented regression model with monthly data points
Participants	Tennessee Medicaid Program N=495,821 to 547,403, included regular NSAID users who received either non‐generic or generic NSAIDs for at least 274 days prior to policy.
Interventions	PA policy on NSAIDs
Outcomes	Health services utilization, Drug costs
Notes	Duration from baseline year: Oct 1, 1988 ‐Sep 30, 1989, post policy: Oct 1, 1989 ‐ Sept 30 1991, no transition period
Risk of bias
Bias	Authors' judgement	Support for judgement
Incomplete outcome data (attrition bias) All outcomes	Low risk	Any difference in the proportion of missing data data in state Medicaid datasets pre to post intervention is unlikely to overturn study results
Selective reporting (reporting bias)	Low risk	All outcomes listed in the methods section are reported in the findings section
Other bias	Low risk
Knowledge of allocated interventions adequately prevented during the study	Low risk	Outcomes are objective measures of healthcare utilization
Intervention independent of other changes	Low risk	Changes in the environment are unlikely to be responsible for magnitude of effect size.Note: In the second year after the policy change Medicaid prescriptions for non‐study drugs increased by 8%, an increase that corresponded to the implementation of the provisions of the Omnibus act of 1990.
The shape of intervention pre‐specified?	Low risk	The point of analysis is the point of intervention; ie, the date the policy intervention was implemented was used to delineate pre and post policy time periods with adequate data points to capture the shape of the pattern of intervention effect over time.
Intervention unlikely to affect data collection?	Low risk	Objective data obtained from an administrative database with standard collection rules