Based on our research, this is the first study to compare the usefulness of different scoring systems for outcome prediction in patients admitted to an ICU with and without cirrhosis by using a score-matched method. In the present study, several clinical characteristics and outcomes of critically ill patients with cirrhosis were compared with those of critically ill patients without cirrhosis with matched APACHE III or SOFA scores. The poor outcome of patients with cirrhosis was consistent with the results of previous studies [12–14]. Recent studies have supported the efficacy of the SOFA scoring system for assessing the extent of organ dysfunction in various groups including critically ill patients with cirrhosis [3–5].
The APACHE III score consisted of the acute physiology score, age, and chronic health problem scores, which are widely used for predicting clinical outcomes currently. Among the patients with cirrhosis, bilirubin levels and incidences of cirrhosis were higher than those among the patients without cirrhosis. Results of the present study suggested that among patients with the same APACHE III score, patients with cirrhosis were older with a higher risk of acidaemia and shock than those without cirrhosis. However, renal function and consciousness status were nonsignificantly different between the 2 groups. The requirement for mechanical ventilation was not included in the APACHE III score, and no difference in the PaO2/FiO2 ratio was observed.
Although the SOFA score includes a fewer number of items and does not assess age and comorbid conditions, it enhances its simplicity and demonstrates high discriminatory power for predicting critically ill patients with cirrhosis. The patients with cirrhosis in the SOFA-matched group showed higher GCS and lower SCr concentrations on Day 1 of ICU admission, whereas these differences were nonsignificant in the APACHE III-matched group. Because patients with cirrhosis typically have higher serum bilirubin levels and lower platelet counts (caused by de novo liver disease), which contribute to a higher SOFA score, than their counterparts do, the patients with cirrhosis with similar SOFA scores may have relatively improved characteristics in the other 5 organic fields. This phenomenon is consistent with our findings showing that the patients with cirrhosis had a more stable neurologic status and renal function than did the patients without cirrhosis in the SOFA-matched group.
APACHE III, a prognostic model, predicts mortality. Prognostic scoring models such as APACHE III assume that mortality is affected by physiological disturbances that occur early in the course of illness, whereas organ dysfunction-scoring systems such as SOFA allow determination of organ dysfunction at the time of admission and at regular intervals throughout the stay in an ICU, thus allowing for the assessment of changes in organ function. The SOFA score is an organ dysfunction score that quantifies the burden of organ dysfunction. Although the SOFA score was originally used to describe morbidity, it was also used in mortality prediction. The accuracy of mortality predictions may be improved with repeated measurements by using organ dysfunction scoring systems such as SOFA.
As shown in Table 4, in the APACHE III-matched group, the SOFA score demonstrated a higher discrimination ability in the patients with cirrhosis than in the patients without cirrhosis (AUROC = 0.810 ± 0.056 vs 0.624 ± 0.060). The SOFA score is simpler for assessment than the APACHE III score by clinicians. Meanwhile, the SOFA score allows for sequential measurements and more accurately reflects the dynamic aspects of disease processes and may provide information of higher quality on the mortality risk. Therefore, the SOFA score is a superior and easier-to-implement model for predicting mortality in the patients with cirrhosis, with a cut-off value of 10 points, providing the optimal overall correctness. In addition, both the SOFA and APACHE III scores are comparable in the patients without cirrhosis.
When the patients with and without cirrhosis were matched by using SOFA scores, difference in APACHE III scores between the 2 groups was nonsignificant in the present study. The RIFLE scoring system, however, showed superior results in patients with cirrhosis to those of the noncirrhotic controls (P = .041) in the SOFA-matched group. The patients with cirrhosis tend to have malnutrition, low muscle mass, and impaired synthesis of creatinine. Therefore, the RIFLE scoring system, which is based on the serum creatinine and urine output, may lead to underestimation of AKI severity and overall illness.
Despite the encouraging results of the present study, several potential limitations should be considered. First, this was a retrospective study performed at a single tertiary-care medical centre, which limits generalisation of the findings. Second, the patients without cirrhosis mainly composed of patients with sepsis and those with a low proportion of patients with other diseases such as cardiovascular disease or acute respiratory distress syndrome. The specificity of the subgroup of the patients with cirrhosis may limit the generalisation. Third, the patient population comprised a high proportion of patients with hepatitis B virus infection. Therefore, this study has limited applicability to typical North American and European patients with hepatitis C virus infection or those with alcohol dependence. Finally, the sample size was insufficient for matching SOFA and APACHE III scores among the patients with and without cirrhosis. Therefore, we cannot draw definitive conclusions regarding the relatively poor short-term prognosis of the patients admitted to the ICU with cirrhosis compared with that of the patients admitted to the ICU without cirrhosis.