Table 2.
Relative differences in rates of health care utilization by type of health record (EHR vs. paper) over time (N = 328)
| Utilization Measure | Incidence Rate Ratios (IRRs)* | |||
|---|---|---|---|---|
| Unadjusted | Adjusted | |||
| IRR (95% CI) | p-value | IRR† (95% CI) | p-value | |
| Primary Care Visits | 1.002 (0.98, 1.02) | 0.85 | 1.02 (0.997, 1.05) | 0.08 |
| Specialist Visits | 0.99 (0.97, 1.01) | 0.26 | 0.96 (0.93, 0.98) | 0.002 |
| Radiology and Other Diagnostic Tests | 0.97 (0.94, 1.01) | 0.10 | 0.96 (0.92, 0.99) | 0.01 |
| Laboratory Tests | 0.98 (0.95, 1.01) | 0.29 | 0.98 (0.95, 1.02) | 0.29 |
| Emergency Department Visits | 1.08 (1.01, 1.14) | 0.02 | 1.04 (0.98, 1.10) | 0.21 |
| Hospital Admissions | 1.05 (0.95, 1.16) | 0.38 | 1.02 (0.93, 1.11) | 0.73 |
| Hospital Readmissions | 1.02 (0.82, 1.26) | 0.88 | 0.97 (0.79, 1.19) | 0.74 |
*The incidence rate ratios (IRRs) are for the interaction between type of health record (EHR vs. paper) and time (2009 vs. 2008). IRRs were generated from negative binomial regression models, except for the IRRs for hospital readmissions, which were generated from zero-inflated negative binomial regression models, with admissions and case mix as predictors of inflation.
† All multivariable models adjusted for gender, age, degree, practice size, plan mix, and practice management system, as these were significant in bivariate models (p<0.20). Multivariable models did not adjust for panel size, because panel size was incorporated into the denominator of the utilization rate (e.g. events per 100 patients). Of the 328 physicians in the study, one was excluded from the multivariate model due to missing data for age.