Probabilities for important variables
| Variable | Base case (range) | Reference studies |
|---|---|---|
| Failure of NOM | 0.25 (0–1.0) | 12 |
| Severe traumatic brain injury (TBI) mortality | 0.27 (0.11–0.41) | 32–34 |
| Multiplier (effect of hypotension on TBI mortality) | 2.4 (1.0–2.4) | 32 |
| Probability of hypotension for NOM | 12 | |
| Probability failure = 0.05 | 0.15 | |
| Probability failure = 0.13 | 0.4 | |
| Probability failure = 0.2 | 0.45 | |
| Probability failure = 0.75 | 0.7 | |
| Probability of hypotension for immediate splenectomy | 0.05 (0–0.15) | 35,36 |
| Mean units RBCs transfused (failed NOM) | 4.1 (0–11) | 12 |
| Mean units of RBCs transfused (successful NOM) | 1.2 (0–4.2) | 12 |
| Mean units of RBCs transfused (immediate splenectomy) | 0.68 (0–1.88) | 35,36 |
| Probability of contracting HIV (per unit RBC) | 0.0000003 | 23 |
| Probability of contracting hepatitis B (per unit RBC) | 0.000012 | 23 |
| Probability of contracting hepatitis C (per unit RBC) | 0.0000002 | 23 |
| Probability of dying from asplenic sepsis (per yr) | 0.0002 (0–0.00034) | 35,36 |
| Probability of fatal surgical complication | 0.03 (0–0.08) | 5 |
| Postoperative complication (yr 1 of cycle) | 0.10 | 37 |
| Persistent postoperative complication (yr 2–38) | 0.005 | 37 |
| Progression of hepatitis B to cirrhosis (per yr) | 0.017 | 28 |
| Progression of hepatitis C to cirrhosis (per yr) | 0.013 | 28 |
| Progression of cirrhosis to death (per yr) | 0.04 | 38 |
| Progression of HIV to AIDS (per yr, yr 1–10) | 0 | 27 |
| Progression of HIV to AIDS (per yr, yr 11–38) | 0.054 | 27 |
| TBI disability upon hospital discharge requiring chronic care | 0.25 | 29 |
| TBI disability upon discharge allowing community living | 0.2 | 29 |
| No measurable TBI disability upon discharge | 0.55 | 29 |
| TBI disability (chronic care) if hypotension occurs | 0.65 | 32–34 |
| No measurable TBI disability if hypotension occurs | 0.15 | 32–34 |
| No change in neurologic state in year 1 after discharge | 0.76 | 29 |
| No change in neurologic state in years 3–38 | 1 | 29 |
NOM = nonoperative management; RBC = red blood cells; TBI = traumatic brain injury.