This study compared the ADAMS [7 (link),8 (link)] dementia diagnosis with Medicare claims records to assess the sensitivity and specificity of Medicare claims to identify true disease as well as to identify the agreement between these two sources of diagnostic information. December 31, 2003 was the date of comparison for Medicare claims records and ADAMS dementia assessment. Persons were classified as having dementia or not based on Medicare claims as of that date, and were also assessed as having dementia or not as of that date. Further, we compared the age of dementia onset, as estimated in ADAMS, to the age of a subject when they first had a Medicare claim that noted dementia. In such cases, persons were categorized as having their initial Medicare claim denoting dementia more than one year prior to dementia onset as estimated in ADAMS; occurring within a year of ADAMS onset; occurring more than one year after ADAMS onset.
Medicare claims records are generated when beneficiaries receive care financed through the program. Such records note not only payment information, but also the date that care was received, diagnosis code information (ICD-9-CM codes) for one primary diagnosis, and several secondary diagnoses. Some files (inpatient hospital claims), have up to 9 secondary diagnosis codes in addition to the primary diagnosis, while others (part B physician supplier claims), have only 3. This study uses the ICD-9-CM codes used in past work to identify dementia in Medicare claims (Appendix 1 ) [19 (link)]. We also conducted sensitivity analyses by adding several additional ICD-9-CM codes suggested by colleagues associated with the ADAMS dementia assessment, but the differences were trivial (e.g., 4 additional cases of dementia identified in claims) so results are shown using the ICD-9-CM codes that were used in past work to increase comparability [20 (link)]. All available Medicare claims records were used to complete the study; inpatient, outpatient; part B physician supplier file; home health; Skilled Nursing Facility (SNF); hospice; and durable medical equipment. Persons having a claim with at least one of the codes (in any position, primary or secondary) listed in the appendix were classified as having dementia. Separate analyses were run for dementia of the AD type, which was defined in Medicare claims by the presence of ICD-9-CM code 331.0.
Cost to the Medicare program was defined as the amount that Medicare actually paid for an episode of care and using all files as noted above, following past work in this area [9 (link),11 (link),12 (link)].
Medicare claims records are generated when beneficiaries receive care financed through the program. Such records note not only payment information, but also the date that care was received, diagnosis code information (ICD-9-CM codes) for one primary diagnosis, and several secondary diagnoses. Some files (inpatient hospital claims), have up to 9 secondary diagnosis codes in addition to the primary diagnosis, while others (part B physician supplier claims), have only 3. This study uses the ICD-9-CM codes used in past work to identify dementia in Medicare claims (
Cost to the Medicare program was defined as the amount that Medicare actually paid for an episode of care and using all files as noted above, following past work in this area [9 (link),11 (link),12 (link)].