Abstract
Objective Several formulas based in different biomarkers may be used to estimate glomerular filtration rate (GRF). However, all of them have some limitations, and it is very important to evaluate their performances in different groups of patients. Therefore, we compared GFR, as estimated by creatinine-based and cystatin C-based equations, according to albuminuria, in type 1 diabetes (T1DM), in an observational case-control study. Subjects and methods T1DM patients were classified according to albuminuria: normoalbuminuric (n = 63), microalbuminuric (n = 30), macroalbuminuric (n = 32). GFR was calculated using creatinine-based and cystatin C-based (aMDRD, CKD-EPIcr, CKD-EPIcys, MacIsaac, Tan and CKD-EPIcrcys) equations. Spearman Correlation was used to evaluate the correlation of GFR estimated by the formulas with albuminuria. ROC curves were constructed to compare AUCs of GFR estimated by equations, in reference to macroalbuminuria. Sensibility, specificity and accuracy were calculated for a cut-off < 60 mL/min/1.73 m2. Results GFR estimated by creatinine-based and cystatin C-based equations significantly differed among normoalbuminuric, microalbuminuric and macroalbuminuric patients. Spearman correlation and AUCs of GFR estimated by creatinine-based and cystatin C-based formulas were very similar to each other, though cystatin C-based equations presented better correlation with albuminuria and higher AUCs than the creatinine-based ones, and the best accuracy to detect macroalbuminuric patients. Conclusion Although GFR estimated by all creatinine-based and cystatin C-based equations permitted the differentiation between T1DM patients, according to albuminuria, cystatin C-based equations presented best accuracy to detect macroalbuminuria in T1DM patients and should be considered in the clinical routine in order to increase the possibility of early diagnostic of chronic renal disease.
Highlights
Diabetic nephropathy is characterized by a progressive increase in urinary albumin excretion (UAE)
Patients with microalbuminuria presented increased levels of urea than patients with normoalbuminuria (p = 0.001) and patients with macroalbuminuria had higher levels of urea, creatinine and cystatin C than the other groups (p < 0.001). eGFR was reduced in patients with microalbuminuria compared to patients with normoalbuminuria, independent of the equation used to estimate glomerular filtration rate (GFR). eGFR was reduced in patients with macroalbuminuria as compared to patients with micro and normoalbuminuria, independent of the equation used to estimate GFR (p < 0.001)
Several biomarkers and formulas based in these biomarkers may be used to estimate GFR and to evaluate renal function
Summary
Diabetic nephropathy is characterized by a progressive increase in urinary albumin excretion (UAE). The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) research group developed a new creatinine-based equation to estimate GFR as an attempt to overcome the limitations of the other formulas [13]. Some authors have suggested that cystatin C-based equations are equal or superior to creatininebased ones and to creatinine clearance, especially to detect early stages of chronic kidney disease [22,23] They emphasize that further studies are necessary to evaluate its efficacy in different groups of patients and that cystatin C serum levels should be interpreted carefully because there are some factors that can affect its levels regardless of the renal function, such as thyroid dysfunction, glucocorticoids use and malignancies [16,17,20].
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