A Comparative study of Glomerular Filtration Rate Calculation by Cockcroft-Gault, MDRD, CKD-EPI Formula and DTPA Renal Scan among live related Kidney Donors

INTRODUCTION: CKD progresses into end stage renal disease (ESRD) inspite of our strategies to slow the progression of the disease. ESRD occurs when kidney function is not able to cope up with the body’s excretory load and hemodialysis, peritoneal dialysis, or kidney transplantation has to be substituted for native kidney function. Among them, kidney transplantation by far imparts a better quality of life in ESRD patients. The shortage of donor organs is a global issue, that restrict kidney transplantation. Hence patients and transplant surgeons are increasingly dependent on live kidney donors. Although kidney transplantation offers a favourable outcome for the recipient, it may be associated with some risk for the donor. To minimize the risks a strict pre-operative donor evaluation is essential. Renal function assessment of the donor is the most important part of donor evaluation. Glomerular filtration rate (GFR) is considered to be optimal test for overall assessment of renal function but serum creatinine is not considered as appropriate and only measurement of renal function, especially for detection of early stages of CKD due to its tubular secretion and also its variability with body mass , age, sex and race. It is well known that GFR can be precisely measured by specific filtration markers such as Inulin, I125 Iothalamate, Cr 51 EDTA,Tc99-diethylene triamino penta acetic acid (DTPA). These standard methods cannot be used in daily clinical practice unfortunately as they are expensive, time consuming and cumbersome and require specialized equipments and skills. So a non invasive and accurate estimation of GFR is the need of the hour in Nephrology. Here comes the GFR prediction equations which are easy to apply, cost effective and less cumbersome. The new K/DOQI Guidelines also recommend estimating GFR by MDRD and COCKCROFT-GAULT equations. Hence, it sounds worthy for me to take up this comparative study of GFR calculation by COCKCROFT-GAULT formula, MDRD formula, CKD-EPI formula and DTPA renal scan among live related kidney donors. AIMS AND OBJECTIVES: 1. To estimate GFR by 3 different methods namely COCKCROFT-GAULT formula, MDRD formula and CKD-EPI formula, among live related kidney donors. 2. To analyse how closely the GFR calculated by these formulae correlate with that of DTPA renal scan in them. MATERIALS AND METHODS: Study Design: observational study. Study Place: Department of Nephrology, Government Stanley Hospital Chennai. Study Period: 6 months from April 2011 to September 2011. Study Population: Individuals attending Nephrology OPD for undergoing evaluation for kidney transplantation. Samle Size : 50 individuals. Sampling : Simple random sampling. Inclusion Criteria: Normal individuals who are willing for kidney donation and undergoing evaluation for the same. Exclusion Criteria: 1. Age 55 years, 2. ABO incompatibility, 3. Donors with h/o HT, DM, 4. Donors with newly detected HT, DM, 5. Females with h/o gestational diabetes and gestational hypertension, 6. Donors with family h/o renal disease. RESULTS: This study included 50 individuals who underwent renal donor workup at the Department of Nephrology, Government Stanley Hospital. Their GFR was calculated by 3 different methods namely COCKCROFT-GAULT formula, MDRD formula and CKI-EPI formula and they were compared with the DTPA renal scan reports. SUMMARY AND CONCLUSIONS: The prediction equations namely Cockcroft-Gault, MDRD and CKD-EPI were found to correlate with the DTPA scan values. • However they underestimated GFR by 27.65%, 27.17% and 22.42% respectively, the possible reasons could be - lack of standardization in calibration of serum creatinine. - study population predominantly being females. - sample size was small. - African–Americans were not included in the study. - MDRD and Cockcroft-Gault were devised in the CKD setting and not in the normal population, our study group belonged to normal and healthy adults. • These prediction equations were not validated in our population and our clinical set up. • DTPA scan gives split GFR of each kidney, renal tubular function, details about renal blood supply, renal tubular obstruction or damage. • DTPA scan cannot be substituted by the prediction equations in special situations like renal transplantation. • However extensive research work are under process, which may bring out newer, more accurate, less invasive and cheaper ways of estimating GFR which can be applicable in all the clinical settings. • Let us hope we achieve that in the near future