Comparison between Cockroft-gault and Mdrd Formula for the Estimation of Glomerular Filtration Rate in Chronic Kidney Disease Patients

The purpose of this study was to determine the concordance between two equations used for estimating glomerular filtration rate, in order to verify the possibility to be used interchangeably in the clinical practice. We present a retrospective study performed on a group of 258 patients with chronic kidney disease treated between January 2008 and December 2009 in the Department of Nephrology of The County Hospital Targu Mures, Romania. For every patient, glomerular filtration rate (GFR) was estimated with Cockroft-Gault (aCG) equation adjusted for body surface (aCG) and abbreviated Modification of Diet in Renal Disease (MDRD) formula (aMDRD). The paired t-test showed that the estimated GFR through the abbreviated MDRD and the corrected CG equations were significantly different from each other (p < 0.0001). There were significant differences between glomerular filtration rate estimated with aCG and aMDRD equations (p<0.0001) between groups of patients of different ages: 4150 years, 51-60 years and 61-70 years, but not in patients under 40 years and over 70 years. 49.22% of the patients with GFR < 60 mL/min/1.73 m using the aCG equation are included in the same GFR interval in MDRD, and only 8.91% of patients had an estimated GFR ≥ 60 mL/min/1.73 m with both formulae. The Pearson correlation coefficient between the aCG and the MDRD equations was good (0.83, p < 0.0001), but the kappa coefficient was 0.48, indicating a low agreement between the 2 formulae. The conclusion of this study is that the Cockroft and MDRD equations cannot be used interchangeably in clinical practice in order to adjust drug doses. Rezumat Studiul de faţă şi-a propus compararea a două ecuaţii de calcul ale ratei de filtrare glomerulară pentru a verifica dacă acestea pot fi folosite interschimbabil în practica medicală. Studiul a fost realizat retrospectiv, pe un grup de 258 pacienţi diagnosticaţi cu boală renală cronică internaţi în Departamentul de Nefrologie a Spitalului Clinic Târgu-Mureş, Romania. Pentru fiecare pacient estimarea ratei de filtrare glomerulară (RFG) a fost realizată folosind ecuaţia Cockroft-Gault corectată pentru suprafaţa corporală şi ecuaţia Modification of Diet in Renal Disease (MDRD) cu patru variabile. Compararea rezultatelor obţinute cu ajutorul celor două formule reliefează existenţa unei diferenţe statistic semnificative (p < 0,0001) atât pentru întregul lot de pacienţi, cât şi pentru grupele de vârstă 41-50 ani, 51-60 ani, 61-70 ani. 49,22% din pacienţii cu RFG < 60 mL/min/1,73 m estimată pe baza ecuaţiei CockroftGault au fost încadraţi în acelaşi interval şi de formula MDRD. 8,91% dintre pacienţi au avut o RFG ≥ 60 FARMACIA, 2011, Vol. 59, 6 761 mL/min/1,73 m calculată cu ajutorul ambelor formule. Coeficientul de corelaţie Pearson între cele două formule a fost 0,83, p < 0,0001, dar indicele kappa a fost 0,48, indicând o concordanţă mică între formule. În concluzie, ecuaţiile Cockroft Gault şi Modification of Diet in Renal Disease nu pot fi utilizate interschimbabil în clinică.