Table 4:

Impact of changes in the after-hours premium on emergency department visits between 2002/03 and 2005/06, using propensity score and entropy balancing weights*

Change in after-hours premiumAll ED visitsVery urgent ED visits
IPW β (95% CI)CBPS β (95% CI)Entropy balancing β (95% CI)IPW β (95% CI)CBPS β (95% CI)Entropy balancing β (95% CI)
Any timing
 0% to 10%0.24 (−0.08 to 0.57)0.25 (−0.08 to 0.57)0.23 (−0.10 to 0.57)0.65 (0.55 to 0.75)0.65 (0.55 to 0.75)0.61 (0.51 to 0.71)
 10% to 15%1.29 (0.96 to 1.62)1.29 (0.96 to 1.62)1.26 (0.93 to 1.60)0.44 (0.34 to 0.54)0.44 (0.34 to 0.55)0.41 (0.30 to 0.51)
Regular hours
 0% to 10%0.19 (0.02 to 0.36)0.19 (0.02 to 0.36)0.16 (−0.01 to 0.34)0.21 (0.16 to 0.26)0.21 (0.16 to 0.26)0.20 (0.14 to 0.25)
 10% to 15%0.69 (0.52 to 0.87)0.70 (0.52 to 0.87)0.67 (0.49 to 0.85)0.17 (0.12 to 0.23)0.17 (0.12 to 0.23)0.16 (0.10 to 0.22)
After hours
 0% to 10%0.06 (−0.19 to 0.30)0.06 (−0.19 to 0.30)0.07 (−0.18 to 0.32)0.44 (0.37 to 0.52)0.44 (0.37 to 0.52)0.41 (0.33 to 0.49)
 10% to 15%0.59 (0.35 to 0.84)0.59 (0.35 to 0.84)0.59 (0.35 to 0.84)0.27 (0.18 to 0.35)0.27 (0.18 to 0.35)0.24 (0.16 to 0.33)
Urgent ED visitsLess-urgent ED visits
IPW β (95% CI)CBPS β (95% CI)Entropy balancing β (95% CI)IPW β (95% CI)CBPS β (95% CI)Entropy balancing β (95% CI)
Any timing
 0% to 10%0.84 (0.66 to 1.02)0.84 (0.66 to 1.02)0.79 (0.60 to 0.98)−1.24 (−1.46 to −1.02)−1.24 (−1.46 to −1.02)−1.16 (−1.39 to −0.94)
 10% to 15%0.87 (0.68 to 1.06)0.87 (0.68 to 1.06)0.83 (0.63 to 1.02)−0.02 (−0.24 to 0.18)−0.02 (−0.24 to 0.18)0.03 (−0.18 to 0.24)
Regular hours
 0% to 10%0.36 (0.26 to 0.46)0.36 (0.27 to 0.46)0.35 (0.24 to 0.45)−0.38 (−0.51 to −0.26)−0.38 (−0.51 to −0.26)−0.38 (−0.50 to −0.25)
 10% to 15%0.39 (0.28 to 0.49)0.39 (0.28 to 0.49)0.37 (0.26 to 0.47)0.13 (0.01 to 0.26)0.14 (0.01 to 0.26)0.14 (0.02 to 0.26)
After hours
 0% to 10%0.47 (0.33 to 0.61)0.47 (0.33 to 0.61)0.44 (0.30 to 0.58)−0.86 (−1.02 to −0.70)−0.86 (−1.02 to −0.70)−0.78 (−0.95 to −0.62)
 10% to 15%0.49 (0.34 to 0.63)0.49 (0.34 to 0.63)0.46 (0.31 to 0.61)−0.16 (−0.31 to −0.01)−0.16 (−0.31 to −0.01)−0.11 (−0.26 to 0.04)
  • Note: CBPS = covariate-balancing propensity score weighting, CI = confidence interval, ED = emergency department, IPW = inverse probability weighting.

  • * Controlled for patient characteristics (patient age, low-income status, and comorbidity using aggregated diagnosis group score), and physician characteristics (physician age, physician age-squared, years since graduation, years since graduation-squared, physician sex, international medical graduation status, and group size) as well as the monthly dummy variable.

  • β coefficients interpreted as the change in the number of ED visits per 1000 patients per month. For confidence intervals, standard errors were clustered at the patient and physician levels.

  • Regular hours refers to 8 am to 5 pm weekdays; after hours refers to 5 pm to 8 am weekdays, and any time on weekends and statutory holidays.