Background: Modifications in physician billing patterns have been shown to occur in response to payer incentives, but the phenomenon remains largely unexplored in billing for anesthesia services. Within the field of anesthesiology, Medicare's policy not to provide additional reimbursement for higher ASA physical status scores contrasts with the practices of most private payers, and this pattern of reimbursement introduces a change in billing incentives once patients attain Medicare eligibility. We hypothesized that, coincident with the onset of widespread Medicare eligibility at age 65 years, a discontinuity in reported ASA physical status scores would be observed after controlling for the underlying trend of increasing ASA physical status scores with age. This phenomenon would manifest as a pattern of upcoding of ASA physical status scores for patients younger than 65 years that would become less common in patients age 65 years and older.
Methods: Using data on age, sex, ASA physical status scores, and type of surgery from the National Anesthesia Clinical Outcomes Registry, we used a quasi-experimental regression discontinuity design to analyze whether there was evidence for a discontinuity in reported ASA physical status scores occurring at age 65 years for the nondeferrable anesthesia services accompanying hip, femur, or lower leg fracture repair.
Results: A total of 49,850 records were analyzed. In models designed to detect regression discontinuity at 65 years of age, neither the binary variable "age ≥ 65" nor the interaction term of age × age ≥ 65 was a statistically significant predictor of the outcome of ASA physical status score. The statistical inference was unchanged when ASA physical status scores were reclassified as a binary outcome (I-II vs III-V) and when different bandwidths around age 65 years were used. To test the validity of our study design for detecting regression discontinuity, simulations of the occurrence of deliberate upcoding of ASA physical status scores demonstrated the ability to detect deliberate upcoding occurring at rates exceeding 2% of eligible cases of patients younger than 65 years.
Conclusions: We found no evidence for a significant discontinuity in the pattern of ASA physical status scores coincident with Medicare eligibility at age 65 years for the nondeferrable conditions of hip, femur, or lower leg fracture repair. Our data do not support the presence of fraudulent ASA physical status scoring among National Anesthesia Clinical Outcomes Registry contributors. If deliberate upcoding of ASA physical status scores is present in our data, the behavior is either too rare or too insensitive to the removal of payer incentives at age 65 years to be evident in the present analysis.