The glomerular filtration rate: comparison of various predictive equations based on serum creatinine with conventional creatinine clearance test in Pakistani population.

Introduction: To compare the conventional creatinine clearance measured on 24-h urine collection with the estimated Glomerular Filtration Rate by Cockcroft & Gault (CG) and Modification of Diet in Renal Disease (MDRD) prediction equations in adults aged 20 years and above in Pakistani population.

Methods: All the patients, including inpatient admitted in hospital and outpatients, more than 20 years of age, reporting for the test of creatinine clearance in clinical chemistry department of Dr. Ziauddin Hospital clinical laboratory from 1st January to 31st December 2006 were studied.

Results: Comparison was made between conventional creatinine clearance and Cockcroft & Gault (CG) and Modification of Diet in Renal Disease (MDRD) prediction equations on 369 cases which revealed strong correlation with conventional creatinine clearance, MDRD equation has better correlation as compared with Cockcroft- Gault creatinine clearance. Statistical correlation was better in cases where serum creatinine was more than 1.50 mg/dl (r = 0.625 for Cockcroft- Gault creatinine clearance and r = 0.724 for MDRD equation) as compared when serum creatinine levels were less than 1.50 mg/dl (r = 0.608 for Cockcroft- Gault creatinine clearance and r = 0.596 for MDRD equation). There was positive bias in both calculated GFRs from conventional creatinine clearance in healthy as well as diseased population.

Conclusion: The creatinine based formulas with their inherent property of convenience and cost effectiveness can be a useful tool for monitoring the progression of disease. They can be applied in clinical practice on our population but they should be interpreted with caution as they over estimate the GFR.