[Compensated creatinine method and glomerular filtration rate estimation in a heterogeneous population of patients].

Creatinine is a metabolite excreted mainly by glomerular filtration, which makes it an important endogenous indicator of kidney function. Creatinine clearance is defined as the ratio of the concentration of creatinine in serum and urine. It assesses glomerular filtration. Creatinine and creatinine clearance have the leading role in the early diagnosis, monitoring and classification of chronic kidney disease. The routine method for determining the concentration of creatinine is the Jaffé photometric method. A newer version is the compensated method. Furthermore, the recommended equation for the estimation of glomerular filtration rate (GFR) is the one based on the MDRD study (eGFR) intended for people over 18 years. The aim of the study was to evaluate how the introduction of the compensated method would affect the clinical use and influence the assessment of GFR in the interpretation of findings and treatment monitoring for people over 20 years. The study group included 130 men and 142 women whose requested laboratory test was creatinine clearance. Data were collected over 20 days at Sestre milosrdnice University Hospital. Serum creatinine concentration and eGFR were determined by the compensated and uncompensated Jaffé method. In conclusion, the compensated creatinine method is not statistically comparable with the uncompensated method, but is clinically fully applicable to the general population above the age of 20, given that the reference intervals are changed. Comparison of eGFR as estimated by the compensated and uncompensated methods to determine creatinine concentration showed the same results as the comparison of clearance. Using the compensated method yielded statistically incomparable results in GFR estimation. However, in clinical practice, patient classification according to stages of chronic kidney disease (CKD) was comparable in the male group according to clearance and eGFR (pi=0.922 and pi=0.230, respectively), while the female group was classified significantly different according to clearance and eGFR (pi<0.016 and pi<0.001, respectively). Switching to the compensated creatinine method while simultaneously applying the eGFR formula was shown to be valid, as patient classification according to CKD stages was comparable (pi=0.921); thus, the methods are reliable for use instead of creatinine clearance in the general population with various diagnoses, which can be noted in all laboratories and which is, although inhomogeneous, routinely used to measure daily creatinine clearance.