**2. Prognosis and prognostic models**

It is essential to quickly and accurately identify those patients most likely to benefit from emergent OLT. In the setting of organ shortage, it is also important to identify and even delist patients who are too ill to benefit from OLT. To minimize the risk of unnecessarily committing individuals to lifelong immunosuppression, one must balance the desire to delay transplantation to allow for the potential of spontaneous recovery against the risk of death with that delay and the risk of the surgery itself. Many ALF patients who have been listed for OLT will recover spontaneously without transplantation and it is estimated that as many as 20% of patients may be transplanted needlessly. In addition, a significant number of ALF patients listed for OLT will die awaiting a donor organ. In the United Kingdom, about 30% of patients initially considered for OLT ultimately become untransplantable following the development of complications (i.e., cerebral edema, sepsis, hemodynamic abnormalities, multiorgan system failure) (Bernal et al., 1998). Additionally, many patients have medical or psychosocial contraindications to transplantation, including irreversible brain injury, underlying cardiovascular disease, infection/sepsis, alcohol or drug abuse, poorly controlled psychiatric disease, or inadequate family support (Simpson et al., 2009). Thus, it is important to identify and delist patients who are too ill to benefit from OLT.

It is crucial that reliable predictive models of survival and the need for OLT be developed. Successfully predicting outcome would allow more judicious use of scarce organs and spare those who will ultimately recover the need for lifelong immunosuppression. There are at present no standardized criteria to predict who should be listed for OLT. Several prognostic models have been developed to help identify appropriate patients for transplantation. Unfortunately, these prognostic models have limitations, and their predictive accuracy varies (Blei, 2005; Anand et al., 1997).
