Study objectives: Investigators have been using
severity-of-illness indexes such as APACHE II (acute physiology and
chronic health evaluation score II) to describe patients with prolonged
critical illness. However, little is known about the utility of these
indexes for this patient population. We evaluated the ability of four
severity-of-illness indexes to predict mortality rates in 182 patients
with prolonged critical illness.
inception cohort study.
Setting: A single, urban,
long-term, acute-care hospital in Chicago.
One hundred eighty-two patients transferred from 37 acute-care hospital
Measurements and results: We assessed four
indexes: the acute physiology and chronic health evaluation II, the
simplified acute physiology score II, the mortality prediction model
II, and the logistic organ dysfunction system using variables measured
on admission to the long-term acute-care hospital ICU. We found that
none of these indexes distinguished well between the patients who lived
and the patients who died (area under ROC [receiver operating
characteristics] curve < 0.70 for all), nor did they assign correct
probabilities of death to individual patients (Hosmer-Lemeshow
goodness-of-fit statistics, p < 0.01 for all).
Conclusions: Investigators and clinicians should use
caution in using severity-of-illness measures developed for acutely ill
patients to describe critically ill patients admitted to long-term care
units. As clinical practice and research focus more on these latter
patients, development of adequately performing severity-of-illness
measures appropriate to this patient population will be