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Table 1 Information collected on all patients who remained in the intensive care unit (ICU) on day 5.

From: A predictive model for the early identification of patients at risk for a prolonged intensive care unit length of stay

Variable Measurement Reference Group* (if applicable)
Day 1   
Acute Physiology Score (APS) Variables Weight determined by most abnormal value within initial first APACHE day, sum of weights equals the APS, which ranges 0 to 252. Five spline terms added. Variables include pulse rate, mean blood pressure, temperature, respiratory rate, PaO2 : FiO2 ratio (or A-aD02 for intubated patients with FIO2 > 0.5), hematocrit, white blood cell count, creatinine, urine output, blood urea nitrogen, sodium, albumin, bilirubin, glucose, acid base abnormalities, and neurological abnormalities based on Glasgow Coma Score. Continuous measure. Three spline terms added in the complex regression model. N/A
Chronic Health Items (CHIs) AIDS, cirrhosis, hepatic failure, immunosupression, lymphoma, leukemia or myeloma, metastatic tumor. Not used for elective surgery patients. Binary variable for > 0 CHIs. Complex model had a binary variable for each CHI separately. N/A
ICU Admission Diagnosis 59 categories Acute Myocardial Infarction
ICU Admission Source Floor, operating/recovery room, other hospital, other admission source. Direct admission
Length of Stay before ICU Admission Square root. Two spline terms added in the complex regression model. N/A
Age Continuous measure. Three spline terms added in the complex regression model N/A
PaO2 : FiO2 Ratio on Day 1 Divided by 10; Continuous measure. Three spline terms added in the complex regression model.. N/A
Emergency Surgery? Binary No
Ventilated on Day 1? Binary No
Unable to Assess Glasgow Coma Score on Day 1? Binary No
Thrombolytic Therapy (for patients with AMI)? Binary No
Rescaled Glasgow Coma Score on Day 1 12 - Glasgow Coma Score N/A
Day 1 ICU Length of Stay Prediction See reference (10) N/A
Readmission to ICU? Binary No
Day 5   
Acute Physiology Score (APS) Variables Same as for day 1 but taken on day 5. Continuous measure. Three spline terms added in the complex regression model. N/A
Ventilated on Day 5? Binary No
Unable to Assess Glasgow Coma Score on Day 5? Binary No
PaO2 : FiO2 Ratio on Day 5 Divided by 10; Continuous measure N/A
Rescaled Glasgow Coma Score on Day 5 12 - Glasgow Coma Score N/A
Delta APS APS on Day 4 - APS on Day 5 N/A
  1. *"Reference Group" refers to the level of a discrete variable that was the default group used in the multivariable regression model.