[Chronic kidney disease in the source documentation of the outpatient clinic Department of Nephrology. Part II. Comparison of the three different methods of glomerular filtration rate estimation].

The aim of the study was to compare three methods of GFR estimation as simplified MDRD formula, Cockcroft-Gault formula and 24 hour urine collection used in evaluation of kidney function. The study was conducted at the outpatient clinic and enclosed 1183 patients aged between 17 and 98 years (mean 64.7) with creatinine level >120 micromol/l and/or creatinine clearance <90 ml/min/1.73 m2, described in detail in part I. After calculation we obtained different mean GFR values adequately to the method: 38.4 +/- 15.13 ml/min/1.73 m2 (simplified MDRD formula), 44.51 +/- 20.59 ml/min/1.73 m2 (Cockcroft-Gault formula) and 45.63 +/- 25.55 ml/min/1.73 m2 (24-h urine collection). Results of the GFR assessment were different according to the applied method of calculation. The smallest data dispersion was observed in GFR values calculated based on abbreviated MDRD formula and the highest when obtained based on to the 24-hour urine collection. The GFR values obtained based on 24 hour urine collection showed positive correlations with BMI (p<0.01), hemoglobine (p<0.01), hematocrite (p<0.01), diastolic blood pressure (p=0.01), albumin (p=0.041), iron (p=0.03), AIAT activity (p=0.01), and negative with age (p<0.01), phosphate (p<0.01), alkaline phosphatase activity (p=0.039), parathormone (p=0.03), potassium (p<0.01) and magnesium (p<0.01). In the group of patients with GFR values below 30 ml/min in comparison with patients with GFR values above 30 ml/min, in all three methods of GFR estimation it was shown significantly higher values of phosphate, potassium, age, and lower hemoglobin, hematocrite. It was shown also in the group with GFR below 30 ml/min values estimated based on Cockcroft-Gault formula and 24 hour urine collection significantly lower BMI.