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Do patients hospitalised in high-minority hospitals experience more diversion and poorer outcomes? A retrospective multivariate analysis of Medicare patients in California

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We investigated the association between crowding as measured by ambulance diversion and differences in access, treatment and outcomes between black and white patients.


Retrospective analysis.


We linked daily ambulance diversion logs from 26 California counties between 2001 and 2011 to Medicare patient records with acute myocardial infarction and categorised patients according to hours in diversion status for their nearest emergency departments on their day of admission: 0, <6, 6 to <12 and ≥ 12 h. We compared the amount of diversion time between hospitals serving high volume of black patients and other hospitals. We then use multivariate models to analyse changes in outcomes when patients faced different levels of diversion, and compared that change between black and white patients.


29,939 Medicare patients from 26 California counties between 2001 and 2011.

Main outcome measures

(1) Access to hospitals with cardiac technology; (2) treatment received; and (3) health outcomes (30-day, 90-day, and 1-year death and 30-day readmission).


Hospitals serving high volume of black patients spent more hours in diversion status compared with other hospitals. Patients faced with the highest level of diversion had the lowest probability of being admitted to hospitals with cardiac technology compared with those facing no diversion, by 4.4% for cardiac care intensive unit, and 3.4% for catheterisation laboratory and coronary artery bypass graft facilities. Patients experiencing increased diversion also had a 4.3% decreased likelihood of receiving catheterisation and 9.6% higher 1-year mortality.


Hospitals serving high volume of black patients are more likely to be on diversion, and diversion is associated with poorer access to cardiac technology, lower probability of receiving revascularisation and worse long-term mortality outcomes.

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