Background: The purpose of this study was to investigate the superiority of serum cystatin C levels over serum urea and creatinine in evaluating kidney functions in intensive care unit patients.

Material and Methods: 65 patients in intensive care unit of Vakif Gureba Hospital and 35 healthy subjects were included in this study. Renal function was evaluated by the RIFLE criteria. Pateints with serum creatinine indicating a renal failure according to the RIFLE criteria were accepted as Group I, if the creatinine levels were within reference range they were named as Group II and healthy individuals were named as Group II. Serum levels of urea, creatinine and cystatin C were measured in all objects.

Results: Mean cystatin C level was 2.44 ± 0.99 mg/L in Group I, 0.81 ± 0.25 mg/L in Group II and 0.77 ± 0.1 mg/L Group III. Initial serum creatinine levels were within the reference range in all the three groups. In Group I, initial cystatin C level mean was 2.44 mg/L; serum creatinine mean was 1.01mg/dL. These values were 0.50 mg/L and 0.86 mg/dL in Group II, respectively. During the follow-up in intensive care unit, mortality in Group I patients, with risk of developing kidney failure according to RIFLE criteria, was 67.5%. This rate was significantly different (p <0.05) than the rate observed in Group II patients (28%). 65 patients in Group I and II were divided in two groups according to their final dignosis as exitus or discharged. The initial mean cystatin C level in patients who have died were found significantly higher than the other group.

Conclusion: Serum cystatin C measurement for determining of the early phase of kidney function disorders is more valuable than the serum creatinine in intensive care units. In addition, high levels of serum cystatin C may be a factor predicting mortality.