Patient level costs are estimated using computerized patient costing systems that initially log individual utilization of inpatient services, and then apply sophisticated cost estimates from the hospital's general ledger. The occurrence of a hospital-acquired diagnosis is identified using a new Australian 'condition-onset' flag for all diagnoses not present on admission. These diagnoses are grouped to yield a comprehensive set of 144 categories of hospital-acquired conditions, using a recently-developed algorithm to summarize data coded with ICD-10-AM.
Standard linear regression techniques are used to identify the independent contribution to inpatient costs of hospital-acquired conditions, taking into account the case mix of a sample of acute inpatients (n = 1,699,997) treated in Australian public hospitals in Victoria (2005/06) and Queensland (2006/07).