Table 1.

Administrative and Clinical Electronic Health Record (EHR) Variables Included in Multivariable Regression Models

Model building steps	Variablesa
Step 0:	Frailty index
Step 1:	Demographics: age, race/ethnicity
Step 2:	Step 1 variables plus:
	- Medical comorbidities: malignancy, liver/respiratory failure, congestive heart failure, cardiovascular disease, serious mental illness including dementia, smoking, chronic obstructive pulmonary disease, cardiac valve disease, arrhythmia, Parkinson’s disease, fall and/or fracture, osteoporosis and/or use of bisphosphonate medication, dialysis, transplant
	- Medications: angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, beta blockers, calcium channel blockers, thiazide or potassium-sparing diuretics, loop diuretics, statins, antiarrhythmics, anticoagulants or platelet inhibitors, nitrates, aspirin, antipsychotics, oral glucocorticoids, antidiabetic medication regimen
	- Health care utilization: hospitalization in the previous year (in VHA, Medicare, or Medicaid data), hospitalization in the previous month (in VHA and Medicare data), admission date, Medicare use within the past year, Medicaid use within the past year, number of medications at admission, number of outpatient encounters in the previous year, home oxygen use
Step 3:	Step 2 variables plus clinical EHR variables:
	- Vital signs: systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI)
	- Laboratory values: hemoglobin A1c (A1c), low-density lipoprotein (LDL), creatinine, estimated glomerular filtration rate (eGFR), proteinuria
Step 4:	Step 3 variables plus:
	- Frailty index

Notes: VHA = Veterans Health Administration.

^aRare covariates occurring in less than 2% of the sample (sex, diagnosis of HIV) were excluded from multivariable models to allow for bootstrap model validation.