Mean number of services per outpatient‡ ED visit200620092012Change in services per year, % (95% CI)P value
 All outpatient visits7.118.058.60+0.25 (0.25 to 0.26)<0.001
 Low intensity outpatient visits5.285.395.22−0.008 (-0.01 to −0.003)0.001
 High-intensity outpatient visits12.8513.3713.68+0.14 (0.13 to 0.15)<0.001
  • *Inpatient services are ICD-9 procedures.

  • †Outpatient services are represented using Current Procedural Terminology/Healthcare Common Procedure Coding System codes.

  • ‡Longitudinal linear regression models were used to estimate the time trend, adjusting for patient age, race, sex and Medicaid eligibility. The yearly estimates were based on binomial regression for hospital and ICU admission rates and negative binomial regression for mean number of services per admission/outpatient visit and used generalised estimating equations to account for clustering at the level of the ED.

  • ED, emergency department; ICD-9, International Classification of Diseases, Ninth Revision; ICU, intensive care unit.