Table 1.

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.