Analytic Support for Researchers:
SEER-Medicare: Identification of Diagnosis & Procedure Codes
One of the challenges of working with claims data is insuring that all of the relevant
diagnostic and procedure codes have been included. Before finalizing a list of codes to
be included in an analysis, it may be worthwhile for a researcher to print a frequency of
the diagnostic/procedure codes that appear in the data. This will aide the investigator
in identifying diagnoses and procedures coded in practice, as these do not always
correspond to the list of codes identified by only reviewing coding manuals. This is a
particularly important issue in using Medicare claims because bills sometimes contain
codes unique to the Centers for Medicare and Medicaid Services (CMS). Including only ICD-9
and CPT-4 codes may result in services being missed and potentially erroneous findings. In
addition, diagnosis and procedure codes change over time. Longitudinal studies should
include the codes that were are relevant for all years of data.
For studies using Part B claims, services and procedures are coded using HCPCS (Healthcare Common Procedure Classification
System). HCPCS codes have three types: Level I HCPCS are composed of the
CPT-4 codes maintained by the American Medical Association; Level II and Level
III HCPCS are codes used only by CMS. These codes always begin with a letter.
Definitions of Level II HCPCS can be downloaded from the CMS Web site and searched by
keywords. Researchers are encouraged to review the Level II HCPCS to insure that
all relevant codes have been included in their analysis. Level III HCPCS, known
as "local codes", are codes used in a specific locality and begin with W, X, Y,
or Z. Documentation of definitions of local codes is sparse and these procedures
cannot be defined.
Chemotherapy, radiation therapy, and screening procedure
codes frequently included in SEER-Medicare analyses are available.