Background: Cystatin C (CyC) is protein (m. w. 13 300), which is produced by nucleated cells, flltered through glomernli and subsequently reabsorbed and degraded in tubuli. Objective: To investigate changes in serum CyC concentration during two low-flux membrane haemodialyses (HD-I, HD-II) and relationship between serum CyC a creatinine concentrations. Patients and methods: Serum CyC was determined in 17 patients on chronic haemodialysis during HD-I and HD-II by immunonephelometric method (Dade Behring, Austria). Results: Significant correlation between serum CyC and creatinine before HD-I and before/after HD-II was found (p < 0.001). Serum CyC before HD-I (medián 6.3 mg/l, 95 % CI 5.5 - 6.7) increased after HD-I (7.1 mg/l, 6.1 - 8.9) (p < 0.001). Serum CyC before HD-II (6.4 mg/1, 5.8 - 7.2) increased after HD-II (8.0 mg/l, 7.3 - 9) (p < 0.001), while serum creatinine decreased after HD-I and HD-II (p < 0.001). There was correlation between the increase in serum CyC and albumin during HD-I (p < 0.001) and HD-II (p < 0.01). Conclusion: There was Glose correlation between serum CyC and creatinine before haemodialyses. Serum CyC increased after haemodialyses, due to CyC non-dialysability through low-flux membrane and haemoconcentration. Unlike creatininaemia, serum CyC reflects the residual renal function even after haemodialyses.

        Key words: Cystatin C - Haemodialysis