Patient safety in ambulatory care has not been routinely measured. California implemented a pay-for-performance program in safety-net hospitals that incentivized measurement and improvement in key areas of ambulatory safety: referral completion, medication safety, and test follow-up. We present two years of program data (collected during July 2015-June 2017) and show both suboptimal performance in aspects of ambulatory safety and questionable reliability in data reporting. Performance was better in areas that required limited coordination or patient engagement-for example, annual medication monitoring versus follow-up after high-risk mammograms. Health care systems that lack seamlessly integrated electronic health records and patient registries encountered barriers to reporting reliable ambulatory safety data, particularly for measures that integrated multiple data elements. These data challenges precluded accurate performance measurement in many areas. Policy makers and safety advocates need to support the development of information systems and measures that facilitate the accurate ascertainment of the health systems, patients, and clinical tasks at greatest risk for ambulatory safety failures.

Patient safety in ambulatory care has not been routinely measured. California implemented a pay-for-performance program in safety-net hospitals that incentivized measurement and improvement in key areas of ambulatory safety: referral completion, medication safety, and test follow-up. We present two years of program data (collected during July 2015-June 2017) and show both suboptimal performance in aspects of ambulatory safety and questionable reliability in data reporting. Performance was better in areas that required limited coordination or patient engagement-for example, annual medication monitoring versus follow-up after high-risk mammograms. Health care systems that lack seamlessly integrated electronic health records and patient registries encountered barriers to reporting reliable ambulatory safety data, particularly for measures that integrated multiple data elements. These data challenges precluded accurate performance measurement in many areas. Policy makers and safety advocates need to support the development of information systems and measures that facilitate the accurate ascertainment of the health systems, patients, and clinical tasks at greatest risk for ambulatory safety failures.