Table 2.
Characteristics Associated with Preoperative Testing before Cataract Surgery.*
| Characteristic | Baseline Patient Characteristics Only | Ophthalmologist Only | Ophthalmologist plus All Other Variables |
|---|---|---|---|
| Adjusted Odds Ratio (95% CI) | |||
| Age† | 1.19 (1.18–1.20) | — | 1.09 (1.08–1.10) |
|
| |||
| Sex | |||
|
| |||
| Male | Reference | — | Reference |
|
| |||
| Female | 1.04 (1.03–1.05) | — | 1.00 (0.98–1.01) |
|
| |||
| Race | |||
|
| |||
| White | Reference | — | Reference |
|
| |||
| Black | 1.04 (1.01–1.06) | — | 0.97 (0.94–1.00) |
|
| |||
| Other | 1.31 (1.28–1.35) | — | 0.94 (0.91–0.98) |
|
| |||
| Charlson comorbidity index score | |||
|
| |||
| 0–1 | Reference | — | Reference |
|
| |||
| 2 | 1.51 (1.49–1.54) | — | 1.56 (1.53–1.59) |
|
| |||
| ≥3 | 2.20 (2.16–2.23) | — | 2.35 (2.31–2.39) |
|
| |||
| U.S. region | |||
|
| |||
| Pacific west | — | — | Reference |
|
| |||
| Northeast | — | — | 1.74 (1.58–1.90) |
|
| |||
| Midwest | — | — | 0.82 (0.75–0.89) |
|
| |||
| South | — | — | 0.77 (0.71–0.83) |
|
| |||
| Mountain west | — | — | 0.54 (0.48–0.60) |
|
| |||
| Population density | |||
|
| |||
| Urban | — | — | Reference |
|
| |||
| Rural | — | — | 0.86 (0.82–0.90) |
|
| |||
| Primary care physicians per 100,000 residents†‡ | — | — | 1.06 (1.03–1.09) |
|
| |||
| Ophthalmologists per 100,000 residents‡ | — | — | 1.22 (1.19–1.25) |
|
| |||
| Ophthalmologist annual cataract surgical volume† | — | — | 0.97 (0.97–0.98) |
|
| |||
| Medicare expenditures per beneficiary in hospital referral region in 2010 U.S. dollars | |||
|
| |||
| Quartile 1: $6,911–$8,689 | — | — | Reference |
|
| |||
| Quartile 2: $8,691–$9,674 | — | — | 1.06 (0.99–1.14) |
|
| |||
| Quartile 3: $9,693–$10,311 | — | — | 1.03 (0.96–1.11) |
|
| |||
| Quartile 4: $10,341–$13,824 | — | — | 1.23 (1.14–1.33) |
|
| |||
| Surgical setting | |||
|
| |||
| Ambulatory surgery center | — | — | Reference |
|
| |||
| Hospital outpatient department | — | — | 1.30 (1.26–1.34) |
|
| |||
| Ophthalmologist§ | — | 3.40 (3.33–3.47) | 2.94 (2.88–2.99) |
The C-statistic for the area under the receiver-operating-characteristic curve was 0.60 for the model that included baseline patient characteristics only, 0.78 for the ophthalmologist-only model, and 0.80 for the model that included the ophthalmologist plus all other variables. The addition of a variable for the presence or absence of an office visit to the ophthalmologist-only model and the model with all variables resulted in C-statistics of 0.84 and 0.85, respectively. A graphical depiction of these results is provided in the Supplementary Appendix.
Age, primary care physicians per 100,000 residents, and surgical volume were divided by 10 to produce more meaningful odds ratios.
The hospital referral region variables were current as of 2006.
The influence of the ophthalmologist was summarized by the median odds ratio, which is the median ratio of the odds of preoperative testing between demographically identical patients of equal health status who are the patients of two randomly selected ophthalmologists (calculated with the use of the total sample of 10,507 ophthalmologists).