Time-dependent error in the APACHE II scoring system.

Using the APACHE II scoring system, the risk of death was calculated for 189 patients in the Wanganui Intensive Care Unit and 194 patients in the Harare Intensive Care Unit. Using tables of actual and predicted outcome, the predictive power of the system was compared in patients grouped according to the length of time that they spent in the ICU. The predictive error increased from 15% in those patients staying less than six days, to 38% in those staying six days or more (P less than 0.01). The predictive accuracy of the APACHE II system appeared to decrease with the length of time the patient stayed in the Intensive Care Unit.