Estimation of the glomerular filtration rate (GFR) is important in clinical practice that too in intensive care setting. Most of the antibiotics and drugs that are used in ICU setting are excreted via the kidney. The MDRD formula and Cockcroft Gault equation are most commonly used to calculate GFR. Usefulness of these formulas in clinical setting is dependent on precision and
bias. So this study is designed to evaluate these formulas with 24 hour urine creatinine clearance in critically ill patients by calculating correlation coefficient.
MATERIALS AND METHODS:
This study was conducted in 100 adult patients of Govt, Rajaji, hospital, Madurai. We estimated Creatinine Clearance by CG and MDRD formula and measured GFR by 24 hrs urine creatinine
clearance. Bland Altman plot was used to find the difference between the paired observations. RESULTS:
The mean GFR measured by 24 hours urine creatinine clearance was 44.75ml/min/1.73m2 (95% CI: 41.13 to 48.37). The mean glomerular filtration rate calculated by Cockcroft-Gault formula was 56.48ml/min/1.73m2 (95%CI: 52.45 to 60.51) and by MDRD formula was 48.71ml/min/m2 (95% CI: 44.80 to 52.62). Correlation coefficient for comparison of CG formula/24 hour urine creatinine clearance and MDRD/24 hour urine clearance were 0.90956 with p value of <0.0001 and 0.9303 with p value of <0.0001 respectively. Bias is defined as the mean difference between
calculated and measured GFR. In our study bias was 11.73ml/min for Cockcroft-Gault equation and 3.961ml/min for MDRD equation. This indicates overestimation of glomerular filtration rate by these two formulas.
CONCLUSION:
C-G and MDRD equations can be an alternative to the CrCl test for assessing GFR, thus avoiding the need for the cumbersome and expensive GFR test. The MDRD formula had greater validity than the C-G equation
