Purpose: The Medicare Chiropractic Services Demonstration was conducted in ninety-three counties from 2005 to 2007. An analysis of budget neutrality (ABN) found that the demonstration was associated with increased total Medicare expenditure of $50 million among chiropractic users. Demonstration sites in Illinois accounted for 98% of the increase in Medicare expenditures among chiropractic users. This study explored the association between chiropractic utilization and total expenditure per beneficiary in general to generate a hypothesis to explain how inclusion of Illinois counties biased the results of the ABN.
Methods: This analysis explored the association between demonstration effects and total concurrent costs to Medicare in all beneficiaries (contextual effects). Medicare data were analyzed to generate descriptive statistics for the ninety-three demonstration counties and matched comparison samples before, during and after the time of the demonstration. Expenditures per beneficiary (EPB) were determined and variation in EPB was quantified. Contextual effects were compared with the demonstration effects.
Results: EPB for all Medicare beneficiaries was consistently higher in Illinois than in other states, and did not vary substantially during the demonstration years. Of the ten sites with the highest EPB in 2006, nine were in Illinois. In Illinois EPB was 228-$373 higher during the demonstration years. There was a congruence between contextual effects and demonstration effects in Illinois that was not observed in the other four demonstration states.
Conclusions: An association between chiropractic costs and all costs in Illinois (not observed in other sites) may have confounded the reported effect of the demonstration in Illinois.
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