Cystatin C As a Marker of Renal Function in Patients with Chronic Intestinal Failure on Long-Term Parenteral Nutrition

Rationale: The estimation of renal function parameters is inaccurate in Chronic Intestinal Failure (CIF) patients on parenteral nutrition (PN). The aim of the present study is to assess the reliability of 3 CKD-EPI GFR estimating equations (eGFR) (Creatinine, Cystatin C or combined Creatinine/Cystatin C) compared to the Iohexol plasma clearance (mGFR) in patients on long-term PN (> 6 months) due to CIF. Methods: Forty-eight patients,median age 58 (22-86) years-old with CIF (23 M/25 F) on PN for a median of 82 months were retrospectivelly studied. We studied their renal function parameters, the causes of CIF and prescription details of the PN. Agreement studies were realized by Pearson correlation and Bland-Altman method (mean bias ±SD). Results: Median mGFR was 65 (26-110) ml/min/1.73m2 and eGFR with CKD-EPI was 85 (28-134) ml/min/1.73m2 for Creatinine, 74 (29-124) ml/min/1.73m2 for Cystatin C and 75 (22-140) ml/min/1.73m2 for Cystatin C/Creatinine based formulas. Despite positive correlations between mGFR and the three eGFR methods, the agreements were not acceptable for clinical practice (mGFR vs eGFRcreat: r(df)=0.861, p<0.001, mean bias: 20.88±14.73 mGFR vs eGFRcys: r(df)=0.902, p<0.001, mean bias: 12.32±13.18, mGFR vs eGFRcreatcys: r(df )=0.914, p<0.001, mean bias:17.65±12.99. Forty-seven percent had a mGFR<60 ml/min/1.73m2 (CKD Stage III or more). There was a significantly positive correlation between mGFR and the duration of CIF [r(df)=0.333, p=0.021] as well as the duration on PN [r(df)=0.281, p=0.05]. There were no other significant correlations between mGFR and the CIF, prescription details of PN, biochemical, body composition as well as muscle functional evaluation parameters. Conclusion: The methods of estimating eGFR seriously miscalculate the true levels of renal function in patients with CIF on PN and could be used with caution in daily clinical practice Disclosure of Interest: None declared