. Author manuscript; available in PMC: 2013 Jul 1.

Published in final edited form as: J Alzheimers Dis. 2009;17(4):807–815. doi: 10.3233/JAD-2009-1099

Table 3.

The effect of errors in claims-based dementia assessment on the cost of dementia and Alzheimer’s disease to the Medicare program (2003)^a

	N	Unadjusted costs^b	Medicare costs, 2003			Part B claims no.	Selected utilization and death, 2003				P^d
	N	Unadjusted costs^b	P^b	Adjusted costs^c	P^c	Part B claims no.	P^d	Hospitalized at least once %	P^d	Died %	P^d
Dementia
True negative	412	4,065	Ref	Ref		22.1	Ref	20.0	Ref	3.1	Ref
False negative	39	6,702	0.37	1,410	0.65	19.7	0.51	25.0	0.46	12.5	0.004
True positive	215	11,251	< 0.001	5,937	< 0.001	24.2	0.26	38.3	< 0.001	14.0	< 0.001
False positive	65	11,294	< 0.001	6,566	< 0.001	29.0	0.02	33.8	0.01	5.9	0.25
Alzheimer’s disease
True negative	497	18,618,517	Ref	Ref		23.0	Ref	22.6	Ref	4.6	Ref
False negative	72	731,059	0.46	155	0.96	23.5	0.85	32.9	0.05	13.9	< 0.001
True positive	117	1,312,071	0.01	2,668	0.20	22.8	0.92	38.9	< 0.001	15.1	< 0.001
False positive	45	937,174	0.64	−809	0.76	28.0	0.14	34.7	0.06	4.1	0.88

ADAMS dementia assessment is used as the standard against which Medicare claims are measured. For example, false negative means that Medicare claims did not identify dementia, while ADAMS did. Analyses exclude 27 subjects who died prior to January 1, 2003.

Unadjusted costs are mean amount spent by Medicare in 2003 for the care of false negative, true positive, and false positive compared individually to true negative cases. P value is for t test of means. Analyses run using sample weights.

Adjusted difference is a regression coefficient showing the increase in Medicare costs associated with being a false negative, true positive, or false positive case as compared to a true negative (omitted group). Regression model analyzed total 2003 Medicare expenditures as dependent variable while controlling for demographic factors (age, sex, race, marital status, income, education), residence (nursing home v. community), controls for death during 2003 and time survived during 2003 (No. months). Analyses run using sample weights.

P is for t test of means of number of Part B claims, percent hospitalized during 2003, and percent dying during 2003.