Miller 2003.

Methods	Multisite RCT (2 sites).
Participants	208 US outpatients and inpatients entering public agencies for treatment of drug problems.
Interventions	1 session MI (n= 104) vs treatment as usual (n= 104).
Outcomes	Physiological primary: Urine toxicology. Non‐physiological primary: Percent days abstinent from illicit drugs and alcohol. Secondary: Retention (frequency of therapy sessions attended).
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Urn randomisation.
Allocation concealment (selection bias)	Unclear risk	The urn randomisation was performed while the client was completing baseline assessment.
Blinding (performance bias and detection bias) Patients and providers	Unclear risk	No blinding but urine toxicology.
Blinding (performance bias and detection bias) Assessors	Low risk	"Assessment for all participants was conducted by experienced interviewing staff of CASAA's Program Evaluation Services unit, who were unaware of treatment group assignment."
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	At 3, 6, 9, and 12 months, attrition was 7%, 14%, 20% and 21%, respectively. Loss was balanced across groups. Reasons not reported. ITT not performed.
Selective reporting (reporting bias)	Unclear risk	Addiction Severity Index was reported in the methods section, but it was not reported in the results section.
Other bias	Unclear risk	Urine drug screens and collateral reports were used to check on self‐report. There is a possibility that the standard care group had received MI. The MI group received one additional session. There were no differences between groups at baseline.