Identifying Code Stacking Among Complex Diagnostic Laboratory Tests in Medicare Claims Data
Objectives: To identify complex diagnostic laboratory tests (CDLTs) billed using code stacking in Medicare claims data and to examine the characteristics of patients receiving tests and payments for tests.
Study Design: Descriptive analyses were used to examine the differences in beneficiary characteristics and Medicare liabilities for beneficiaries receiving 1 of 130 CDLTs in 2011.
Methods: We used 100% Part B Medicare claims from 2011, Medicare Denominator enrollment data, and Healthcare Common Procedure Coding System (HCPCS) stacks for laboratories to analyze the stacking HCPCS codes in Medicare claims for 4 laboratories and 130 CDLTs that fell into 6 groups. We focused on identifying stacks in Medicare fee-for-service claims data and examining the characteristics of patients receiving tests and payments for tests.
Results: The quantities, or stacks, of HCPCS codes for tests billed by each laboratory differ for the same test, resulting in substantial variation in payment amounts across laboratories and tests.
Conclusions: Stacking test codes for billing has made it difficult for third-party payers and health services researchers to identify access to, cost of, and the comparative effectiveness of CDLT tests. This research shows that it is possible to identify these tests in claims data and that stacking leads to large variations in payments for similar tests.