Economic Effect of Following HbA1c Testing Practice Guidelines in the Elderly Medicare Population: An Instrumental Variable Analysis

Abstract

This retrospective follow-up study aimed to evaluate the effect of following glycated hemoglobin (HbA1c) testing practice guidelines on Medicare expenditures. The authors identified 12 635 incident diabetes patients from 1998 and 1999 Medicare 5% claims data and calculated Medicare payments from 2000 to 2003. They applied a 2-stage least-squares model with instrumental variable (IV) methodology to estimate the effect of receiving ≥2 HbA1c tests annually on Medicare expenditures. Only 27.7% (3503/12 635) of the sample received ≥2 HbA1c tests annually. IV estimation results showed that receiving the tests was associated with a $953 decrease in Medicare payments per patient-year. Improved HbA1c test rates could save Medicare costs. For each year, 2000 to 2003, the authors estimate that approximately $174 million in Medicare expenditures could have been saved through Medicare patients aged ≥67 years who developed diabetes in 1998 and 1999, had no diabetes complications at baseline, and subsequently did not receive ≥2 HbA1c tests annually.