Comparison of Infection Probability Score, APACHE II, and APACHE III Scoring Systems in Predicting Need for Ventilator and Ventilation Duration in Critically Ill Patients

Background: This study examines the efficacy of the predicting power for need for mechanical ventilation and duration of mechanical ventilation of three different scoring systems in a medical-surgical intensive care unit. Methods: One-hundred eighty critically ill patients were included prospectively in our study in a consecutive period of seven months. On the day of admission, data were collected from patients to compute the Acute Physiology and Chronic Health Evaluation (APACHE) II and III, and Infection Probability Score (IPS). The sensitivity, specificity, and overall correctness of prediction were calculated, and the cut-off point giving the best likelihood ratio was determined. The area under receiver operating characteristic curve was computed. Results: For prediction of need for mechanical ventilation the best cut-off points were 52 for APACHE III, 12 for APACHE II, and 12 for IPS. The area under the curve was 0.89 in APACHE III, 0.74 in APACHE II and 0.82 in IPS. There were statistical differences between APACHE III, APACHE II and IPS in terms of likelihood ratio and the area under the curve (P < 0.05). None of the three scoring systems provide good discrimination in prediction of more than 5 days respiratory support under mechanical ventilation. Conclusion: For prediction of need for mechanical ventilation, the APACHE III has better accuracy than APACHE II or IPS.