This analytical cross-sectional study of 148 patients admitted to a surgical/trauma ICU assessed how effectively APACHE IV, SAPS III, and SOFA scores predicted patient outcomes such as ICU mortality and the length of ICU stay. Our findings demonstrate that the APACHE IV score was the only significant discriminating predictor of mortality, and the SAPS III was the only significant discriminating predictor of survival based on 24-h values after admission to the ICU. Moreover, the APACHE IV score was superior to the SAPS III and SOFA scores regarding accuracy, while the three scores were similar in calibration for mortality prediction. We also observed a significant positive correlation between the APACHE IV score with the length of ICU stay, whereas the SAPS III and SOFA scores showed no significant correlation and length of ICU stay.

Our results are consistent with those of a recent study that aimed to assess and compare the predictive value of the APACHE II, APACHE IV, and SAPS II scores for predicting inhospital mortality in the emergency department and found that APACHE IV was superior to the APACHE II and SAPS II in terms of discrimination and calibration (Rahmatinejad et al. 2020). Furthermore, Bennett et al. (Bennett et al. 2019) demonstrated the predictive ability of the APACHE IV score in CICU patients, concluding that the APACHE IV predicted mortality model at 24 h had the highest AUC value of 0.82 (95% CI, 0.81–0.84) for hospital death with good discrimination, followed by APACHE III 0.81 (95% CI, 0.80–0.83) (P = 0.001). However, calibration for hospital death prediction was suboptimal for both the APACHE III score (P = 0.01) and the APACHE IV (P < 0.001). The discriminatory performance of the APACHE IV model was extremely good and similar to that of the APACHE II, SAPS III, and Korean SAPS III models, according to a retrospective study evaluating electronic medical records for patients admitted to the SICU, although all of the models had poor calibration (Lee et al. 2014).

The SAPS-III score was originally designed to assess disease severity and predict mortality of patients treated in surgical ICUs and not as a predictor of survival following ICU admission. We found that SAPS III was also useful in predicting survival in our population of SICU patients, which was an interesting finding. Sakr et al. (Sakr et al. 2008) discovered that SAPS III had a good discriminating capability but poor calibration using prospectively collected data from 1851 patients hospitalized in a surgical intensive care unit. The difference between their findings and ours could be because their study only included postoperative patients, whereas ours included polytraumatic patients. Furthermore, the smaller population size and prospective SAPS-III data calculation in our study may contribute to discrepancies.

In a retrospective cohort study, both APACHE III and APACHE IV had better discriminatory capability but were less calibrated than SAPS III in predicting inhospital mortality, which contradicts our findings, which estimate ICU mortality rather than hospital mortality (Keegan et al. 2012).

Our results are generally in line with a prospective cohort study in a CICU for predicting outcomes; both SOFA and APACHE II scores exhibited excellent discriminative capacity, with AUCs ranging from 0.84 (SOFA) to 0.92 (APACHE II) (Argyriou et al. 2015). Furthermore, the SOFA score was highly recommended for predicting the outcomes of ICU trauma patients in a study of 706 patients admitted to the ICU with significant trauma because it was more easily and simply calculated than the APACHE II and Trauma and Injury Severity Scores (TRISS) (Hwang et al. 2012).

Additionally, Ma et al. (2017) discovered that the SAPS-III score of non-survivors was significantly greater than that of survivors. Our findings revealed that non-survivors scored higher on APACHE IV, SAPS III, and SOFA scores, which is consistent with a clinical study done in respiratory ICU (RICU) that found that APACHE IV and SAPS II scores were significantly higher between non-survivors than survivors on admission, but APACHE IV score showed a negative correlation with RICU stay, in contrast to our findings, which showed a significant mild positive correlation between the APACHE IV score and ICU stay (El-naggar, Raafat, and Mohamed 2018). This disparity could be attributed to the different variety of patients in their RICU and our SICU. Another study in RICU revealed that the mean ± SD admission SOFA score differed significantly between the survivors and non-survivors (4.95 ± 2.49, 6.11 ± 2.76; P = 0.028, respectively) (Galal et al. 2013).

Moreover, non-survivor cases exhibited significantly lower systolic and diastolic blood pressure, as well as a higher body temperature, than survivors. In terms of laboratory findings, arterial blood gas analysis results showed that the mean PO2, SpO2, and PaO2/FiO2 levels in non-survived patients were significantly lower than in survived cases. The average PaCO2 and FiO2 values in dead patients were higher than in living cases. Non-survived patients also had lower 24-h urine output and a considerably greater incidence of vasopressor and mechanical ventilation demands on ICU admission than survived ones. Likewise, Hwang et al. (Hwang et al. 2012) found that in major trauma patients admitted to the ICU, non-survivors had a lower O2 index, systolic blood pressure, and GCS scale.

Our research included several limitations. First, the study involving a single SICU may have limited generalization to other ICUs due to bias in the case mix. Second, our study had a relatively small sample size.