Diagnostic Pathways to Alzheimer Disease: Costs Incurred in a Medicare Population.

Despite its implications on the personal and policy level, little is currently known about the specific diagnostic pathways that patients with cognitive impairment (CI) pass through before being diagnosed with Alzheimer disease (AD). Four major diagnostic pathways were identified in the Medicare claims records for 2001 to 2006: AD as initial diagnosis, cognitive disturbance followed by AD; dementia with suspected etiologies followed by AD; dementia without known cause followed by AD; and 1 triple pathway, cognitive disturbance followed by dementia without known cause followed by AD. For all of these pathways, previously low medical costs peaked during patients' month of initial diagnosis and then declined to a level substantially higher than before. The 3 CI pathways that transition to AD included another peak in costs when a secondary AD diagnosis occurred. Each time, inpatient and skilled nursing facility services were major cost contributors. The primary diagnoses on Medicare claims for the AD event were usually comorbidities rather than CI. A linear regression model adjusting for demographic factors, selected comorbidities, and overall frailty found that the transitional CI diagnoses were significant independent cost determinants. They increased Medicare expenditures by an estimated $4600 to $14,200 relative to patients whose initial CI diagnosis was AD.