Estimation et mesure du débit de filtration glomérulaire : en quête de précision

Chronic kidney disease - Epidemiology collaboration equations even using cystatin C overestimate renal function in patients with chronic intestinal failure on long-term parenteral nutrition

BACKGROUND & AIMS

Accurate determination of renal function is of utmost importance in chronic intestinal failure (CIF) patients on parenteral nutrition (PN) and creatinine based glomerular filtration rate (GFR) estimating equation is used in clinical practice. The aim of the present study is to evaluate the reliability of 3 CKD-EPI GFR estimating equations (eGFR) (creatinine, cystatin C or combined creatinine/cystatin C) compared with the reference method which is Iohexol plasma clearance (mGFR) in patients on long-term PN (>6 months) owing to CIF.

METHODS

Forty-eight patients (25 F) with a median age of 58 years (Interquartile Range:15) presenting CIF on PN for a median duration of 93 months (75) were included in this retrospective study. Concordance studies were performed by Pearson correlation and Bland-Altman method (Mean bias-Confidence Interval). Accuracy of the formulas was estimated with P30 representing the proportion of eGFR within 30 % of mGFR (±30 %).

RESULTS

Median mGFR was 65 (29) ml/min/1.73 m2 and the median eGFR was 85 (43) ml/min/1.73 m2 with 2009 CKD-EPIcreatinine, 74 (47) ml/min/1.73 m2 with 2012 CKD-EPIcystatin and 75 (48) ml/min/1.73 m2 with 2012 CKD-EPIcombined Cystatin C/Creatinine based formulas. The agreements were not acceptable for clinical practice. Median bias as well as lower and upper confidence intervals were for mGFR vs. eGFR (2009 CKD-EPIcreat): +21,1 (16.7,25.3), for mGFR vs. eGFR (2012 CKD-EPIcyst): +14.4 (12.9,20.5) and for mGFR vs. eGFR (2012 CKD-EPIcomb): +9.3 (7.9,15.5). Accuracy of all formulas estimated by P30 was less than 80 %. With the 3 eGFR equations, more than 46 % of patients were poorly stratified according to the classification of chronic kidney disease (CKD) with an overall tendency towards underestimation of the disease severity. Forty-seven percent of the patients had mGFR<60 ml/min/1.73 m2 corresponding to CKD Stage III or worse.

CONCLUSIONS

The eGFR estimating CKD-EPI equations significantly miscalculate the true levels of renal function in patients with CIF on PN and should be used with caution in daily clinical practice.

Cystatin C and eGFRCKD-EPI-CysC: novel biomarkers for renal impairment diagnosis and two-year progression-free survival in multiple myeloma

To evaluate cystatin C (CysC) and estimation of glomerular filtration rate (GFR) calculated using the formula, CKD-EPI-CysC (eGFRCKD-EPI-CysC) for renal impairment diagnosis and predicting the prognosis of patients with multiple myeloma (MM). One hundred-fourteen patients with MM and 38 healthy individuals were recruited for the study. Data on clinical characteristics and renal function-related biochemical indicators were collected and analyzed. Patients with MM had increased levels of CysC (1.25 (0.97-2.31) vs. 0.84 (0.80-0.92), respectively, p < 0.001) and decreased levels of eGFRCKD-EPI-CysC (53.0 (24.4-81.1) vs. 97.2 (87.0-104.5), respectively, p < 0.001), compared with healthy individuals. There were significantly more patients with elevated CysC levels than with elevated sCr levels (64.9% vs. 41.2%, respectively, p < 0.001). The CKD-EPI-CysC formula detected more patients with eGFR < 60 ml/(min × 1.73 m2) than the CKD-EPI-sCr formula (52.63% vs. 37.72%, respectively, p < 0.001). Correlation analysis found that only CysC, eGFRCKD-EPI-CysC, and eGFRCKD-EPI-sCr-CysC strongly correlated with β2-microglobulin in group ISS-I. Logistic regression analysis was used to screen CysC (OR = 1.495, 95% CI = 1.097-2.038, p = 0.011) and eGFRCKD-EPI-CysC (OR = 0.980, 95% CI = 0.967-0.993, p = 0.003) as independent prognostic indicators for 2-year-progression-free survival (PFS) of patients with MM. Receiver operating characteristic curve analysis found that CysC values >1.70 mg/L had 67.6% sensitivity and 65.2% specificity and eGFRCKD-EPI-CysC values <38.62 ml/(min × 1.73 m2) had 65.2% sensitivity and 67.6% specificity for 2-year PFS of patients with MM. In summary, CysC and eGFRCKD-EPI-CysC were more sensitive than sCr and eGFRCKD-EPI-sCr for predicting renal impairment in patients newly diagnosed with MM. Increased CysC and decreased eGFRCKD-EPI-CysC levels were effective predictors of 2-year PFS of patients with MM.