Predictive value of cystatin C for the identification of illness severity in adult patients in a mixed intensive care unit.

Objectives: This study compared serum cystatin C (CysC) with conventional biomarkers of renal function in terms of their ability to predict illness severity in patients in a mixed intensive care unit (ICU). The present study also tested the hypothesis that increased CysC could predict illness severity in different clinical conditions in adult patients admitted to the ICU.

Design And Methods: The performance of serum creatinine, urea and CysC, as well as the Glomerular Filtration Rate (GFR) estimates (Cockcroft-Gault/MDRD/Larsson and CKD-EPI Equations) in predicting illness severity was compared in 60 critically ill patients. Adult patients admitted to the hospital were screened for eligibility in this prospective and observational study. The mean patient age was 52±19years. The average APACHE II score was 9.5±6 for the entire sample. The patients were assigned to two different degrees of severity, and the internally derived cut off value was an APACHE II score<10 or ≥10.

Results: Both serum CysC and urea showed significant correlations with APACHE II, even after controlling for age. Urea and CysC levels, as well as the GFR estimated by the method of Larsson and Cockcroft-Gault, remained significantly increased in patients in the APACHEII ≥10 group. The ROC curve analyses indicated that both urea and CysC levels have high sensitivity and specificity in the prediction of illness severity using the APACHE II as a gold standard prognostic stratification system. Furthermore, CysC was more accurate than the Larsson, CKD-EPI CysC, CKD-EPI Cr-CysC, Cockcroft-Gault and CKD-EPI Cr CFR estimation methods compared with the MDRD method. Additionally, CysC was a good predictor in both young and old patients, whereas urea was not predictive of illness severity.

Conclusions: Our findings suggest that CysC and GFR estimates (Larsson or CKD-EPI CysC methods) are good predictors of illness severity in adult patients hospitalized in a mixed ICU.