Introduction: The degree of glomerular filtration rate determines the stages of chronic renal disease and, therefore, knowledge on its estimation is essential.
Aims: Two standardized creatinine based estimated glomerular filtration rate equations and five equations based on the immunoturbidimetric determination of cystatin C were compared.
Methods: The distribution of the analytes and the equations, their relations, as well as the differences among the estimated glomerular filtration rates and their chronic kidney disease stages assignments were studied.
Results: The equations based on cystatin C classified more patient into stage 1, while the creatinine based ones more into stages 2, 3 and 4. The equations published as Grubb1, Grubb2 and Larsson classified more patients while the equations created by Tan and Sjöström classified fewer into stage 5 compared to the creatinine based equations. The equations of Grubb1 and Grubb2 resulted in the most similar stage assignment. The occurrence of stages between 3 and 5 was the lowest using the equation of Sjöström.
Conclusions: The different equations for the estimation of glomerular filtration rate modify significantly the chronic kidney disease stage assignment which may have an influence on the treatment and outcome measures of the patients.