Table 2.

Summary Description of All Model Covariates in Study of CDI as a Proxy for Length of Stay

Variable	Description/specification
Hospital characteristics
Bed size	Small, medium, or large
Control/ownership	Public, private (nonprofit), private (for profit)
Region	Northeast, Midwest, South, West
Teaching status/location	Rural, urban nonteaching, urban teaching
RN percent	Percentage of RNs among all licensed nurses
Nurse to patient ratio	Number of total licensed nurse full-time equivalents per 100 inpatient-days
Patient characteristics
Age group	21 indicators for 5-year age ranges
Sex	Female or male
Race	White, black, Hispanic, Asian or Pacific Islander, Native American, or other
Admission type	Emergency, urgent, elective, newborn, trauma center, other
Disposition	6 indicators for routine, transfer to short-term hospital, other transfer, home healthcare, against medical advice, or unknown
OR procedure	Indicator of major OR procedure
Neonatal or maternal diagnosis/procedure	Indicators for maternal, neonatal, or both maternal and neonatal records
Admission month	12 monthly indicators
Admission weekend	Indicator of weekend admission
Died	Indicator of hospital death
Comorbidities	29 comorbid disease indicatorsa
Number of procedures	30 indicators for the total number of procedures coded on discharge record
Number of diagnoses	30 indicators for the total number of diagnoses coded on discharge record
Number of chronic conditions	30 indicators for the total number of unique chronic diagnoses reported on the discharge
APR DRGsb	316 APR DRG indicators
APR DRG risk mortalityb	4 indicators for likelihood of dying: minor, moderate, major, or extreme
APR DRG severityb	4 indicators for severity of illness (loss of function): minor, moderate, major, or extreme
Primary expected payer	Medicare, Medicaid, private insurance, self-pay, no charge, or other
ZIP code median income	4 quartile indicators for estimated median household income in patient’s ZIP code

Note. APR, All Patient Refined; CDI, Clostridium difficile infection; DRG, diagnosis-related groups; OR, operating room; RN, registered nurse.

^aThe 29 comorbidity indicators were assigned by the Agency for Healthcare Research and Quality Comorbidity Software, version 3.7.

^bThe variables for APR DRGs along with APR DRG severity and APR DRG risk mortality were created using software developed by 3M Health Information Systems, version 27.0, for year 2009 and version 28.0 for years 2010 and 2011.