Tools for predicting risk of mortality in the ICU setting: Do we need a crystal ball or rose colored glasses?

Hematopoietic stem cell transplantation (HSCT) applied to children is assoc iated with high risk for organ failure, ICU admission, morbidity and mortal ity. "Respiratory failure" after HSCT carries a historically grave prognosi s. Factors associated with high risk for critical care complications in HSC T patients have been identified, but are dependent on timing and intensity of interventions. Several ICU severity of illness scoring systems predict p rognosis on the basis of physiologic stability, organ system involvement, a nd intensity of supportive measures; but these tend to underestimate posttr ansplantation mortality risk. Adjustment of scoring systems and logistic re gression factor analysis are promising adjuncts, but have not been adequate ly validated. Specific endpoints such as death, length of ICU or hospital s tay, and neurologic function are relatively easy to quantify; but, quality of life is difficult to assess and report. What constitutes "heroic therapy " in one institution may qualify as "routine" care in another. Therefore, t ools to predict mortality in the pediatric HSCT recipient requiring intensi ve care are difficult to apply to the individual patient, and remain more a n art than science. This manuscript attempts to briefly define and review t he pertinent types of PICU severity of illness and mortality prognosis scor ing systems, and their application to pediatric HSCT patients. Pitfalls in application of physiology, organ system failure, therapeutic intensity, dis ease specific, and history-based scoring systems are discussed. Prospective validation studies for severity of illness systems and the evolution to co ncurrent registry-style data collection and analysis are necessary for the HSCT patient requiring ICU care.