Undercoding of Alzheimer's disease and related dementias in hospitalized elderly patients in Italy.

The prevalence of Alzheimer's disease (AD) and AD-related dementias (ADRD) in acute ward-hospitalized elderly patients is not well known, owing principally to misclassification and undercoding of AD and ADRD on hospital discharge abstract forms (DAFs). The aims of this study were to evaluate the prevalence of AD and ADRD, as evaluated by the DAF in elderly patients hospitalized in acute wards, and to compare clinical severity, length of stay, comorbidity, and number of diagnostic procedures in patients with AD versus ADRD to explain the different reimbursement costs of DRG12 (AD) versus DRG429 (ADRD). From the inpatient DAF database of the Casa Sollievo della Sofferenza Hospital, the DAFs of patients aged 65 years or over discharged from January 1, 2001, to March 31, 2003, with principal or secondary diagnoses of AD (ICD9-CM code 331) or ADRD (ICD9-CM codes from 290.