Table 2.
Comparison of baseline characteristics across quartiles of the instrumental variable
| Variable | Physician Visits | Quartile of Facility Visits, Instrumental Variablea | ||||||
|---|---|---|---|---|---|---|---|---|
| 0–3 Visits (n=12,291) | ≥4 Visits (n=14,332) | Standardized Difference | 1st | 2nd | 3rd | 4th | Standardized Difference (1st versus 4th) | |
| Demographic | ||||||||
| Men (%) | 44.1 | 46.0 | 3.7 | 45.6 | 45.8 | 45.8 | 46.2 | 1.2 |
| Age (yr) | 68.9 | 68.2 | 5.8 | 68.4 | 68.1 | 68.4 | 68.3 | 0.4 |
| American Indian (%) | 0.4 | 0.5 | 0.6 | 0.7 | 0.3 | 0.5 | 0.4 | 4.0 |
| Black (%) | 30.2 | 34.3 | 8.8 | 31.0 | 35.8 | 32.6 | 32.1 | 2.5 |
| White (%) | 67.0 | 63.1 | 8.1 | 64.3 | 62.0 | 65.3 | 66.5 | 4.7 |
| Other race (%)b | 2.4 | 2.1 | 1.7 | 4.1 | 1.9 | 1.5 | 1.0 | 19.7c |
| Hispanic ethnicity (%) | 7.2 | 8.4 | 4.6 | 9.1 | 7.4 | 7.8 | 8.1 | 3.7 |
| Socioeconomic and comorbid conditions (%) | ||||||||
| Alcohol use | 2.7 | 1.8 | 6.1 | 2.4 | 2.2 | 1.9 | 2.0 | 2.7 |
| Drug use | 5.7 | 4.1 | 7.0 | 5.1 | 4.7 | 4.7 | 4.6 | 2.7 |
| Smoker | 9.1 | 8.0 | 3.8 | 8.0 | 9.0 | 9.1 | 8.9 | 3.2 |
| Cerebrovascular disease | 45.4 | 41.2 | 8.6 | 42.1 | 43.4 | 43.6 | 41.1 | 2.1 |
| Peptic ulcer disease | 29.1 | 26.8 | 5.1 | 28.0 | 28.4 | 26.8 | 27.2 | 1.7 |
| Coronary artery disease | 39.0 | 36.2 | 5.9 | 38.9 | 37.6 | 36.7 | 35.4 | 7.2 |
| Heart failure | 82.4 | 78.8 | 9.2 | 81.2 | 81.2 | 80.3 | 79.2 | 4.9 |
| Pulmonary disease | 52.1 | 48.2 | 7.7 | 50.1 | 50.3 | 50.0 | 48.1 | 3.9 |
| HIV infection | 1.1 | 0.9 | 1.5 | 1.4 | 1.2 | 0.8 | 0.7 | 6.8 |
| Cancer | 17.6 | 14.7 | 7.8 | 15.6 | 16.2 | 15.7 | 14.7 | 2.6 |
| Dementia | 19.3 | 14.3 | 13.2c | 15.7 | 17.2 | 16.6 | 14.7 | 2.9 |
| Diabetes | 70.7 | 69.3 | 3.1 | 69.4 | 71.4 | 70.2 | 69.2 | 0.4 |
| Liver disease | 13.6 | 12.6 | 3.0 | 13.3 | 13.5 | 13.0 | 12.5 | 2.3 |
| Paralysis | 6.4 | 5.2 | 5.1 | 5.3 | 5.8 | 6.2 | 5.0 | 1.0 |
| Periperal vascular disease | 52.0 | 48.8 | 6.5 | 49.6 | 51.5 | 49.7 | 49.9 | 0.4 |
| Rheumatic disease | 5.4 | 5.0 | 2.1 | 5.0 | 5.5 | 5.0 | 5.1 | 0.5 |
| Acuity of care and facility | ||||||||
| First year of hemodialysis (%) | 14.7 | 13.1 | 4.7 | 14.9 | 13.5 | 13.0 | 12.7 | 6.4 |
| Duration of hospitalization (d) | 12.0 | 8.9 | 22.5c | 9.9 | 9.6 | 9.9 | 9.8 | 0.6 |
| Facility size (n patients) | 98.2 | 105.7 | 14.3c | 100.1 | 99.9 | 104.3 | 106.2 | 11.4c |
See Supplemental Tables 3, 7, 11, and 15 for assessment of the instrumental variable in secondary cohorts.
a
n=6653 for each quartile.
b
Includes Pacific Islander, Middle Eastern, Indian Subcontinent, Asian and other/multiracial.
c
Greater than 10% standardized difference between comparison groups.