The impact of information disclosure on quality of care in HMO markets.

OBJECTIVE: To examine the impact of voluntary information disclosure on quality of care in Health Maintenance Organization (HMO) markets in the USA.
SETTING: Commercial HMOs that collected a set of standardized quality meausures, Health Plan Employer Data and Information Set (HEDIS), between 1997 and 2000 in the USA (1062 HMO-years). After collecting the HEDIS data, some HMOs disclosed their HEDIS-quality scores to the public (disclosing HMOs), whereas some HMOs declined to disclose the information (non-disclosing HMOs).
DESIGN: A secondary data analysis based on 4 years of quality scores of HMOs. The study uses non-disclosing plans as a control group. A treatment-effects model is used to address a potential bias associated with voluntary disclosure decisions by HMOs. MAIN OUTCOME MEASURE(S): The study focuses on 13 HEDIS clinical indicators. On the basis of these indicators, a plan-level composite score and four domain scores were constructed. The four domains are childhood immunizations, treatments/exams for chronic conditions, screening tests and maternity services.
RESULTS: Public disclosure leads to an increase of 0.72 composite score units, which corresponds to ∼7% points in original quality scale (0-100%). The degree of quality improvement differed by the type of services.
CONCLUSIONS: Public release of quality information had a significant and positive effect on quality in HMO markets during the earlier years of the voluntary disclosure program; however, the improvement was not universal across all quality measures.