Using health outcomes to validate access quality measures.

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.