In 2011, 12.3 percent of Medicare hospital admissions were followed by a potentially preventable readmission, according to the Medicare Payment Advisory Commission (MedPAC), which has just released its latest Report to Congress on Medicare and the Health Care Delivery System. To be clear from the outset, not all potentially preventable admissions can be avoided. A classification system developed by 3M Health Information Systems and discussed in the MedPAC report defines a potentially preventable readmission “as a readmission that is clinically related to the initial hospitalization in that the underlying reason for the readmission may be plausibly related to the care during and immediately after a prior hospital stay.  A clinically related readmission may have resulted from a process of care or treatment during the prior admission or from a lack of postdischarge follow-up rather than from unrelated events that occurred after the prior admission.” Preventing readmissions typically depends more on primary...