Proteinuria, (99m) Tc-DTPA Scintigraphy, Creatinine-, Cystatin- and Combined-Based Equations in the Assessment of Chronic Kidney Disease

Background. Precise estimation of the glomerular filtration rate (GFR) and the identification of markers of progression are important. We compared creatinine, cystatin, and combined CKD-EPI equations with (99m)Tc-DTPA scintigraphy to measure GFR and proteinuria as markers of progression. Methods. Cross-sectional, observational study including 300 subjects. CKD was classified by (99m)Tc-DTPA scintigraphy. Determinations. Creatinine, 24-hour creatinine clearance, cystatin, Hoek formula, and creatinine, cystatin, and combined CKD-EPI equations. Results. In the global assessment, creatinine CKD-EPI and combined CKD-EPI equations yielded the highest correlations with (99m)Tc-DTPA: ρ = 0.839, P < 0.0001 and ρ = 0.831, P < 0.0001. Intergroup analysis versus (99m)Tc-DTPA: control G, creatinine clearance ρ = 0.414, P = 0.013; G3, combined CKD-EPI ρ = 0.5317, P < 0.0001; G4, Hoek ρ = 0.618, P < 0.0001, combined CKD-EPI ρ = 0.4638, P < 0.0001; and G5, creatinine clearance ρ = 0.5414, P < 0.0001, combined CKD-EPI ρ = 0.5288, P < 0.0001. In the global assessment, proteinuria displayed the highest significant correlations with cystatin ( ρ = 0.5433, P < 0.0001) and cystatin-based equations (Hoek: ρ = -0.5309, P < 0.0001). When GFR < 60 mL/min: in stage 3, proteinuria-cystatin ( ρ = 0.4341, P < 0.0001); proteinuria-Hoek ( ρ = -0.4105, P < 0.0001); in stage 4, proteinuria-cystatin ( ρ = 0.4877, P < 0.0001); proteinuria-Hoek ( ρ = -0.4877, P = 0.0026). Conclusions. At every stage of GFR < 60 mL/min, cystatin-based equations displayed better correlations with (99m)Tc-DTPA. Proteinuria and cystatin-based equations showed strong associations and high degrees of correlation.