Table 1.
Characteristics of patients in the derivation and validation cohorts
| Characteristica | Derivation (n = 19 831) | Validation (n = 19 773) | |
|---|---|---|---|
| Age, y (mean) | 61.3 (17.7) | 61.1 (17.5) | |
| Male | 9 207 (46.4) | 9 182 (46.4) | |
| Race | White | 12 361 (62.3) | 12 344 (62.4) |
| Black | 3 911 (19.7) | 3 985 (20.2) | |
| Hispanic | 2 762 (13.9) | 2 670 (13.5) | |
| Payor, | Medicare | 8 191 (41.3) | 8 005 (40.5) |
| Medicaid | 1 371 (6.9) | 1 414 (7.1) | |
| Commercial | 7 556 (38.1) | 7 473 (37.8) | |
| Self-Pay | 944 (4.8) | 1 019 (5.2) | |
| Elective admission | 2 823 (14.2) | 2 770 (14.0) | |
| At least 1 prior hospitalization in past year | 4 495 (22.7) | 4 489 (22.7) | |
| At least 1 prior ED visit in past year | 5 653 (28.5) | 5 715 (28.9) | |
| Number of emergency contacts in EMR (up to 5) | |||
| 0 | 643 (3.2) | 654 (3.3) | |
| 1 | 16 107 (81.2) | 16 000 (80.9) | |
| 2 | 2 846 (14.4) | 2 865 (14.5) | |
| 3 – 5 | 235 (1.2) | 254 (1.3) | |
| Principal diagnosis disease category | |||
| Cardiorespiratory condition | 2 631 (13.3) | 2 482 (12.6) | |
| Cardiovascular condition | 2 425 (12.2) | 2 549 (12.9) | |
| Neurologic condition | 1 104 (5.6) | 1 098 (5.5) | |
| Comorbidities (available within 24 h of admission)b | |||
| Coronary atherosclerosis or angina, cerebrovascular disease | 2 423 (12.2) | 2 518 (12.7) | |
| Diabetes mellitus | 2 254 (11.4) | 2 317 (11.7) | |
| Congestive heart failure | 1 504 (7.6) | 1 474 (7.5) | |
| Iron deficiency | 1 344 (6.8) | 1 380 (7.0) | |
| Acute renal failure | 1 261 (6.4) | 1 237 (6.3) | |
| Disorders of fluid, electrolyte, acid-base | 1 214 (6.1) | 1 241 (6.3) | |
| Arrhythmias | 1 205 (6.1) | 1 204 (6.1) | |
| Psychiatric disease | 979 (4.9) | 990 (5.0) | |
| Chronic obstructive pulmonary disease | 766 (3.9) | 782 (4.0) | |
| Pneumonia and other infectious diseases | 737 (3.7) | 745 (3.8) | |
| Laboratory results/vitals within 24 h of admission, median (IQR) | |||
| Albumin | 3.5 (3.1 – 3.9) | 3.6 (3.1 – 3.9) | |
| Creatinine | 1 (0.8 – 1.4) | 1 (0.8 – 1.4) | |
| Hematocrit | 37.7 (33.4 – 41.3) | 37.6 (33.3 – 41.2) | |
| Potassium | 4.1 (3.8 – 4.5) | 4.1 (3.8 – 4.5) | |
| Respiratory rate | 20 (20 – 24) | 20 (20 – 24) | |
| Systolic blood pressure | 155 (139 – 176) | 154 (139 – 176) | |
| Reported pain level on scale of 0 – 10 | 0 (0 – 4) | 0 (0 – 4) | |
| Outcomes | |||
| 30-day mortality | 621 (3.1) | 548 (2.8) | |
| 30-day readmission | 2 638 (13.3) | 2 504 (12.7) | |
| 30 day readmission or mortality | 3 116 (15.7) | 2 906 (14.7) | |
| Length of stay, median (IQR) | 4 (2 – 7) | 4 (2 – 6) | |
Abbreviations: EMR, electronic medical record; IQR, interquartile range. aNumbers (percent) unless otherwise stated bComorbidities for admissions in the prior year, not index admission, coded using ICD-9 diagnoses