Table 1.
Distribution of continuous and discrete variable use among ML studies.
| Predictor variables | Outcome variables | Total | Continuous* | Discrete | Reference |
|---|---|---|---|---|---|
| Age, Motor GCS score, w, CT class, Traumatic subarachnoid hemorrhage, Epidural hematoma, Hypoxia, Hypotension, Glucose, Sodium, Hemoglobin | Death vs. Unfavorable Outcome (GCS < 4) | 11 | 5 | 6 | (228) |
| Age, Female, Primary mechanism of injury (Fall, Road traffic accident, Struck by projectile, Non-accidental injury), Loss of consciousness, LOC > 1 min, Difficult arousal, Vomiting, Seizure activity, Confusion/Disorientation, (Preverbal) irritability, (Verbal) Headache, (Verbal) Amnesia, Signs of altered mental status, Presence of unequal pupils, Clinical signs of skull fracture, Signs of base skull fracture, Presence of scalp hematoma, Frontal injury, Presence of scalp laceration, (Preverbal) with open fontanelle, Tense fontanelle | Predicted Risk Scores (0–100) | 21 | 1 | 20 | (224) |
| Mean arterial pressure, Cerebral perfusion pressure, Intercranial pressure, Glasgow coma scale | Death vs. Survival | 4 | 4 | 0 | (226) |
| Age, GCS (hospitalization), Injury severity score, Temperature, Systolic pressure, Diastolic pressure, Open brain injury or not, Concussion presence, Brain contusion presence, Brain-stem injury presence, Contrecoup presence, Epidural hematoma presence, Subdural hematoma presence, Hematoma volume, Intracerebral hematoma presence, Brain hernia presence, Oxygen saturation, Infection complication presence, Presence of other complications, Number of surgeries, Length of stay, Length of ICU stay, Multiple trauma presence, Tracheotomy presence, Period of mechanical ventilation, Aspiration presence, GCS (discharge), Previous TBI occurrence, Hypothermia presence, Acidosis presence, Presence of hospital-acquired pneumonia, White blood cell count, Dose of glucose, Glucocorticoid use, Nasogastric tube use, Coagulation change, Parenteral nutrition use, Lipid emulsion use, Enteral nutrition time, Sequelae or not | Death vs. Survival | 40 | 10 | 30 | (227) |
| Age, Sex, Helmet-wearing status, Coronary artery disease (CAD), Congestive heart failure (CHF), Cerebral vascular accident (CVA), Diabetes mellitus (DM), End-stage renal disease (ESRD), Hypertension (HTN) GCS score, Temperature, Systolic blood pressure (SBP), Heart rate (HR), Respiratory rate (RR) | Death vs. Survival | 13 | 5 | 8 | (230) |
| Age, Gender, Race, Mechanism of injury, Blood pressure, Heart rate, GCS on arrival to the emergency department (ED), CT scan findings, Injury severity score (ISS), The AIS per body region, Intubation status and location, Date/time of injury, Time of admission to the ED, Patients’ known comorbidities, Performed procedures, Blood transfusion, In-hospital complications, Outcome and date of disposition | Risk of Prolonged Medical Ventilation (PMV) PMV > 7 days vs. < 7 days PMV > 10 days vs. < 10 days PMV > 14 days vs. < 14 days |
18 | 4 | 14 | (223) |
| Subcortical, Auditory, Sensorimotor, Cerebellum, Visual, Salience, Executive control, Default mode network, Precuneus, language resting state networks | mTBI vs. No mTBI | 10 | 0 | 10 | (231) |
| Glucose, Hemoglobin, Albumin, C-reactive protein, Sodium, Urea, Magnesium, Lactate, Venous pH, White cell count (total), Neutrophil count, Hematocrit, Prothrombin time, Activated partial thromboplastin time | Favorable GOS (4–5) vs. Unfavorable GOS (1–3) | 14 | 14 | 0 | (232) |
| GCS, Systolic blood pressure (SBP), Abnormal pupillary response, Major extracranial injury, Cerebral contusion, Acute subdural hematoma (ASDH), Traumatic subarachnoid hemorrhage (TSAH), Epidural hematoma, and Skull fracture, Glucose, C-reactive protein, Fibrin/fibrinogen degradation products (FDP), Marshall CT classification | Poor Outcome vs. Good Outcome | 13 | 4 | 9 | (233) |
| GCS score, Systolic blood pressure, Heart rate, Respiratory rate, Temperature, Hematocrit, Age, Sex, Intubation status, ICD-9-CM injury E-code, and Injury severity score | Death vs. Survival | 11 | 6 | 5 | (234) |
| GCS score, Motor score, Eye-opening, Verbal response, Pupillary light reaction, Glucose level, Hemoglobin, Mass lesions, Cisterns, Midline shift >5 mm | Favorable (Alive with GOS > 3 at 6 months) vs. Unfavorable (Death or GOS < 3 at 6 months) | 11 | 2 | 9 | (235) |
| Neutrophil gelatinase-associated lipocalin (NGAL), N-terminal proB-type natriuretic peptide (NT-proBNP), Urine output (UOP), Plasma creatinine | Acute Kidney Injury vs. No Acute Kidney Injury | 4 | 4 | 0 | (236) |
| (After reduction) FA 2-OH C16:0, FA C18:0, TUDCA, PE ae C36:4, LysoPC a C20:4 | mTBI vs. No mTBI | 5 | 5 | 0 | (237) |
| Age (< 65, 65) Gender, Histology (Adenocarcinoma, Squamous cell carcinoma, Large cell carcinoma, Undifferentiated carcinoma), T status, (T1, T2, T3), Regional lymph node status, (N0, N1, N2), Stage (I, II, III, IV), Grade (Low, Medium/high), Border of bronchus (Positive, Negative), FEV1 < 70%, Positive vessel infiltration, Positive lymphatic infiltration, Positive pleural infiltration, Chemotherapy adjuvant, Radiotherapy adjuvant, High expression of P53, High expression of caspase 3, High expression of-H2AX, High expression of Ki67 | Death vs. Survival | 32 | 0 | 32 | (238) |
*It should be noted that, unless otherwise specified, “Age” was treated as a continuous variable. However, it is hard to describe subjects’ age as being purely continuous because age is rarely reported as a continuous variable in most clinical settings. GCS, Glasgow Coma Score; CT, Computed Tomography; ICU, Intensive Care Unit; TBI, Traumatic Brain Injury.