Table 1. Baseline characteristics of index admissions stratified by presence of 30-day readmission.
z - Charlson/Deyo co-morbidity index (CCI) was calculated as per Deyo classification.
* Variables are AHRQ co-morbidity (cm_) measures.
x- Represents a quartile classification of the estimated median household income of residents in the patient’s ZIP Code, derived from ZIP Code-demographic data obtained from Claritas. The quartiles are identified by values of 1 to 4, indicating the poorest to wealthiest populations. Because these estimates are updated annually, the value ranges vary by year. http://www.hcupus.ahrq.gov/db/vars/zipinc_qrtl/nisnote.jsp.
# -HMO: Health Maintenance Organization.
{- The bed size cutoff points divided into small, medium, and large have been done so that approximately one-thirdof the hospitals in a given region, location, and teaching status combination would fall within each bed size category. State and County QuickFacts. Washington, DC: US Census Bureau; 2012.
| Index Admission | No Readmission | Readmission | p value | |
| Total population (unweighted) | 24,307 | 19,837 | 4,470 | |
| Total population (weighted) | 53,555 | 43,748 | 9,807 | |
| Patient level variables | ||||
| Age (%) | 0.08 | |||
| ≥85 | 14 | 14 | 13 | |
| 65-84 | 29 | 29 | 30 | |
| 45-64 | 39 | 40 | 40 | |
| 18-44 | 16 | 17 | 17 | |
| Gender (%) | 0.09 | |||
| Female | 52 | 53 | 52 | |
| Male | 47 | 47 | 48 | |
| CCIz (%) | .001 | |||
| 0 | 18 | 19 | 13 | |
| 1-3 | 56 | 56 | 53 | |
| 4-6 | 19 | 18 | 26 | |
| 7-9 | 5 | 5 | 7 | |
| 10-12 | 1 | 1 | 1 | |
| 13-15 | 0.05 | 0.05 | 0.05 | |
| ≥16 | 0.06 | 0.00 | 0.01 | |
| Length of stay (%) | .001 | |||
| 1-3 | 29 | 31 | 25 | |
| 4-6 | 28 | 28 | 26 | |
| 7-9 | 16 | 16 | 17 | |
| 10-12 | 8 | 8 | 9 | |
| 13-15 | 5 | 5 | 7 | |
| ≥16 | 12 | 11 | 15 | |
| Comorbidities (%) * | ||||
| Drug abuse | 4 | 4 | 5 | 0.08 |
| Hypertension | 61 | 60 | 63 | .001 |
| Hypothyroidism | 15 | 15 | 16 | 0.004 |
| Liver disease | 4 | 4 | 5 | .001 |
| Fluid and electrolyte disorders | 44 | 43 | 50 | .001 |
| Metastatic cancer | 4 | 3 | 5 | 0.003 |
| Neurological disorders | 12 | 12 | 13 | 0.12 |
| Obesity | 16 | 17 | 15 | 0.07 |
| Peripheral vascular disorders | 8 | 8 | 10 | .001 |
| Psychoses | 5 | 5 | 7 | 0.001 |
| Pulmonary circulation disorders | 5 | 6 | 6 | 0.3 |
| Renal Failure | 22 | 20 | 28 | .001 |
| Valvular disease | 7 | 7 | 8 | 0.28 |
| Alcohol abuse | 5 | 5 | 5 | 0.26 |
| Rheumatoid arthritis/ collagen vascular diseases | 4 | 4 | 4 | 0.58 |
| Chronic blood loss anemia | 1 | 1 | 2 | 0.12 |
| Congestive heart failure | 18 | 17 | 22 | .001 |
| Chronic pulmonary disease | 19 | 19 | 20 | 0.15 |
| Depression | 13 | 13 | 13 | 0.99 |
| Diabetes, uncomplicated | 25 | 24 | 27 | 0.002 |
| Diabetes with chronic complications | 7 | 7 | 10 | .001 |
| Median household income (%) x | 0.1 | |||
| 76-100th | 27 | 26 | 28 | |
| 51-75th | 26 | 26 | 24 | |
| 26-50th | 25 | 25 | 25 | |
| 0-25th | 21 | 22 | 21 | |
| Primary Payer (%) | .001 | |||
| Self-pay/no charge/other | 63 | 63 | 67 | |
| Private including HMO# | 11 | 10 | 13 | |
| Medicaid | 18 | 19 | 15 | |
| Medicare | 8 | 8 | 5 | |
| Hospital bed size (%) { | 0.02 | |||
| Large | 11 | 11 | 10 | |
| Medium | 24 | 25 | 23 | |
| Small | 65 | 64 | 67 | |
| Hospital teaching status (%) | 0.05 | |||
| Non-metropolitan hospital | 32 | 32 | 32 | |
| Metropolitan teaching | 58 | 58 | 59 | |
| Metropolitan non-teaching | 10 | 10 | 9 | |
| Admission type (%) | ||||
| Elective | 91 | 90 | 93 | |
| Non elective | 9 | 10 | 7 | |
| Disposition (%) | .001 | |||
| Against medical advice | 50 | 52 | 42 | |
| Facilities | 22 | 21 | 24 | |
| Home health care | 27 | 26 | 32 | |
| Home | 1 | 1 | 2 |