Creatinine- vs. cystatin C-based equations compared with 99mTcDTPA scintigraphy to assess glomerular filtration rate in chronic kidney disease.
BACKGROUND
In chronic kidney disease (CKD), accurate estimation of the glomerular filtration rate (GFR) is mandatory. Gold standard methods for its estimation are expensive and time-consuming. We compared creatinine- versus cystatin C-based equations to measure GFR, employing (99m)Tc-DTPA scintigraphy as the gold standard.


METHODS
This was a prospective cross-sectional observational study including 300 subjects. CKD was defined according to K/DOQI guidelines, and patients were separated into groups: stage 1 (G1), n=26; stage 2 (G2), n=52; stage 3 (G3), n=90; stage 4 (G4), n=37; stage 5 (G5), n=60; and control group, n=35. Creatinine-based estimates were from 24-hour creatinine clearance using the Walser formula, Cockcroft-Gault, MDRD-4 and CKD-EPI; cystatin C equations used were Larsson, Larsson modified equation, Grubb and Hoek.


RESULTS
Age and body mass index were different among groups; proteinuria, hypertension, diabetes and primary glomerulopathies significantly increased as CKD worsened. In the global assessment, CKD-EPI and Hoek gave the highest correlations with (99m)Tc-DTPA: rho=0.826, p<0.001 and rho=0.704, p<0.001, respectively. Most significant linear regressions obtained: CKD-EPI vs. (99m)Tc-DTPA, Hoek vs. (99m)Tc-DTPA and CKD-EPI vs. Hoek. However, important differences emerged when each group was analyzed separately. Best significant correlations obtained with (99m)Tc-DTPA: control group, creatinine clearance rho=0.421, p=0.012; G1, Crockoft-Gault rho=0.588, p=0.003; G2, CKD-EPI rho=0.462, p<0.05; G3, CKD-EPI rho=0.508, p<0.001; G4, Hoek rho=0.618, p<0.001; G5, CKD-EPI rho=0.604, p<0.001.


CONCLUSIONS
At GFR <60 ml/min, CKD-EPI and Hoek equations appeared to best correlate with (99m)TcDTPA. In controls and at early stages of CKD, creatinine-based equations correlated better with (99m)Tc-DTPA, with CKD-EPI being the one with the best degree of agreement.
Department of Nephrology, British Hospital of Buenos Aires, Buenos Aires, Argentina. htrimarchi@hotmail.com
Hernán
H
Trimarchi
Alexis
A
Muryan
Diana
D
Martino
Agostina
A
Toscano
Romina
R
Iriarte
Vicente
V
Campolo-Girard
Mariano
M
Forrester
Vanesa
V
Pomeranz
Clara
C
Fitzsimons
Fernando
F
Lombi
Pablo
P
Young
María S
MS
Raña
Mirta
M
Alonso
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood / Q000652:urine; D016009:Chi-Square Distribution; D003404:Creatinine / Q000097:blood* / Q000652:urine*; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000652:urine; D012307:Risk Factors; D012720:Severity of Illness Index; D016284:Technetium Tc 99m Pentetate; D055815:Young Adult
D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D019275:Radiopharmaceuticals; D003404:Creatinine; D016284:Technetium Tc 99m Pentetate