Since 2003, the Lombardy region has introduced a case-mix reimbursement system for nursing homes based on the SOSIA form which classifies residents into eight classes of frailty. In the present study the agreement between SOSIA classification and other well documented instruments, including Barthel Index, Mini Mental State Examination and Clinical Dementia Rating Scale is evaluated in 100 nursing home residents. Only 50% of residents with severe dementia have been recognized as seriously impaired when assessed with SOSIA form; since misclassification errors underestimate residents' care needs, they determine an insufficient reimbursement limiting nursing home possibility to offer care appropriate for the case-mix.