Improving the cost-effectiveness of health care requires an understanding of the genesis of health care costs and in particular the sources of cost variation. Little is known about how multiple physicians, caring collaboratively for patients, contribute to costs.


To explore the effect of collaborative care by physicians on variation in discretionary costs in an intensive care unit (ICU) by determining the contributions of the attending intensivists and ICU fellows.


Prospective, observational study using a multivariable model of median discretionary costs for the first day in the ICU, adjusting for confounding variables. Analysis included 3514 patients who spent more than 2 hours in the ICU on the initial day. Impact of the physicians was assessed via variables representing the specific intensivist and ICU fellow responsible on the first ICU day and allowing for interaction terms.


On the initial day, patients spent a median of 10.6 hours (interquartile range, 6.3–16.5) in the ICU, with median discretionary costs of $1343 (interquartile range, $788–2208). There was large variation in adjusted costs attributable to both the intensivists ($359; 95% CI, $244–$474) and the fellows ($756; 95% CI, $550–$965). The interaction terms were not significant (P = .12–.79).


In an ICU care model with intensivists and subspecialty fellows, both types of physicians contributed significantly to the observed variation in discretionary costs. However, even in the presence of a hierarchical arrangement of clinical responsibilities, the influences on costs of the 2 types of physicians were independent.

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