BACKGROUND: Medicare payment reforms will reimburse accountable care 
organizations (ACOs) for providing high-quality healthcare. Quality measures 
that reliably predict health outcomes are required.
OBJECTIVES: To compare the ability of alternative wait time measures to predict 
glycated hemoglobin (A1C) levels among diabetes patients.
STUDY DESIGN: This retrospective observational study relied on Veterans Health 
Administration utilization data and Medicare claims data from 2005 to 2010.
METHODS: Outcomes included an average A1C level and uncontrolled A1C. Heckman 
selection models simultaneously predicted the presence of an A1C value and its 
level. Models were risk adjusted for prior individual health status. The main 
explanatory variables of interest were facility-level primary care wait times 
measured in days. Several measures were tested, including capacity measures and 
retrospective and prospective time stamp measures. The time stamp measures used 
either the date the appointment was created in the scheduling system (create 
date) or the date the patient or provider desired the appointment (desired date) 
as the start date for wait time computation. All measures were calculated 
separately for new and returning patients.
RESULTS: New patient capacity and create date measures significantly predicted 
outcomes, but desired date measures did not. The returning patient retrospective 
create date and desired date wait time measures significantly predicted higher 
and uncontrolled A1C, but capacity and prospective create date measures did not.
CONCLUSIONS: Different administrative wait times predict A1C for new and 
returning patients. To properly measure quality, ACOs should use wait time 
measures that demonstrate relationships with outcomes for subpopulations of 
patients.