Table 3.
Absolute differences in rates of health care utilization by type of health record (paper vs. EHR) over time (N = 328)
| Utilization Measure | Observed Mean Rates (SD) per 100 Patients | Estimated Mean Differences in Rates (95% CI) per 100 Patients | |||
|---|---|---|---|---|---|
| 2008 | 2009 | Observed Difference 2009 – 2008* | Estimated Difference 2009 – 2008† | Estimated Difference in Differences† | |
| Primary Care Visits | |||||
| • Paper | 314.8 (95.0) | 322.8 (100.7) | 8.0 (3.0, 13.0) | 9.7 (4.2, 15.2) | |
| • EHR | 286.4 (58.0) | 294.2 (68.3) | 7.8 (3.5, 12.3) | 16.6 (10.2, 23.1) | 6.7 (-0.9, 14.4) |
| Specialist Visits | |||||
| • Paper | 338.0 (95.9) | 357.2 (100.6) | 19.2 (14.0, 24.3) | 18.5 (11.4, 25.6) | |
| • EHR | 332.2 (102.4) | 346.9 (106.0) | 14.7 (9.7, 19.7) | 3.4 (-3.9, 10.7) | -14.4 (-23.6, –5.2) |
| Radiology and Other Diagnostic Tests | |||||
| • Paper | 219.9 (56.5) | 219.8 (53.1) | -0.1 (-4.8, 4.4) | 2.8 (-2.5, 8.2) | |
| • EHR | 209.7 (61.9) | 204.0 (55.9) | -5.7 (-10.7, –0.7) | -6.5 (-12.1, –0.9) | -9.2 (-16.3, –2.2) |
| Laboratory Tests | |||||
| • Paper | 1270.3 (438.7) | 1350.2 (466.5) | 79.9 (51.0, 108.8) | 100.8 (71.0, 130.6) | |
| • EHR | 1258.6 (392.7) | 1314.5 (387.1) | 55.9 (25.7, 86.2) | 74.2 (38.5, 109.9) | -23.3 (-66.3, 19.7) |
| Emergency Department Visits | |||||
| • Paper | 18.8 (12.3) | 18.8 (13.1) | 0.0 (-0.8, 0.8) | 0.2 (-0.6, 1.0) | |
| • EHR | 23.5 (14.6) | 25.3 (18.8) | 1.8 (0.6, 3.0) | 0.9 (0.2, 1.7) | 0.7 (-0.4,1.8) |
| Hospital Admissions | |||||
| • Paper | 7.7 (4.3) | 7.0 (4.3) | -0.7 (-1.2, –0.2) | -0.3 (-0.9, 0.2) | |
| • EHR | 8.8 (4.4) | 8.3 (4.5) | -0.5 (-1.0, 0.2) | -0.2 (-0.7, 0.3) | 0.1 (-0.6, 0.8) |
| Hospital Readmissions‡ | |||||
| • Paper | 1.7 (1.5) | 1.4 (1.4) | -0.3 | ||
| • EHR | 1.8 (1.8) | 1.6 (1.8) | -0.2 | ||
*Observed absolute mean differences with 95% confidence intervals were calculated using negative binomial regression, adjusting for clustering by provider but not adjusting for co-variates.
† Estimated absolute mean differences with 95% confidence intervals were calculated using negative binomial regression, adjusting for clustering by provider and adjusting for co-variates (gender, age, degree, practice size, plan mix, and practice management system). Of the 328 physicians in the study, one was excluded from the multivariate model due to missing data for age.
‡The model for hospital readmissions was generated with zero-inflated negative binomial regression, with admissions and health plan as the predictors causing inflation. Because readmissions were so rare, it was not possible to generate stable estimates of the 95% confidence intervals for observed differences, nor was it possible to generate stable estimates of the estimated differences.