Austin 2004B.

Methods	Study design: ITS
Participants	Physicians Clinical speciality: not clear Level of training: fully trained Setting/country: not clear/Canada
Interventions	The PEM was the ALLHAT, published on 18 December 2002, which concluded that thiazide‐type diuretics should be the first‐step antihypertensive therapy, compared with either calcium channel blockers or ACE inhibitors
Outcomes	4 process outcomes (prescribing): relative market share of ACE inhibitors/angiotensin receptor blockers relative market share of β‐blockers relative market share of diuretics relative market share of calcium channel blockers (each outcome as percentage of market share before and after publication of ALLHAT)
Notes	‐
Risk of bias
Bias	Authors' judgement	Support for judgement
Intervention independent of other changes ‐ ITS	Unclear risk	No information was provided
Shape of Intervention effect pre‐specified ‐ ITS	Unclear risk	Quote, pg. 44: "The Antihypertensive and Lipid‐Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), published on December 18, 2002, concluded that thiazide‐type diuretics should be the first‐step antihypertensive therapy, compared with either calcium channel blockers (CCBs) or angiotensin converting enzyme (ACE) inhibitors. We examined trends in incident use of antihypertensive agents following publication of the ALLHAT trial"
Intervention unlikely to affect data collection ‐ ITS	Low risk	The intervention (publication of the ALLHAT study in 2002) did not affect either the source or method of data collection
Blinding of outcome assessors (detection bias) ‐ ITS All outcomes	Low risk	The outcome was objective
Incomplete outcome data (attrition bias) ‐ ITS All outcomes	Low risk	Quote, pg. 44: "we studied claims for antihypertensive agents that were submitted to the Ontario Drug Benefit (ODB) program between January 1, 1992, and April 30, 2003. The ODB program tracks prescriptions dispensed to all 1.3 million residents of Ontario older than 65 years.antihypertensive agents following publication of the ALLHAT trial"
Selective reporting (reporting bias) ‐ ITS	Low risk	All relevant outcomes in the methods section were reported in the results section
Other bias ‐ ITS	Low risk	There was no evidence of other risks of bias