<prompt> GFR is calculated as:GFR mlminute per 1.73 m2 kxheightserum creatinineGFR mlminute per 1.73 m2 kxweightserum creatinineGFR mlminute per 1.73 m2 kweightxcreatinineGFR mlminute per 1.73 m2 kheightxcreatinine  <response>: Ans. A. GFR mlminuteper1.73m2kxheightserumcreatinineAn accurate and reliable method for assessment of renal function is essential for children with kidney diseases. Serum creatinine based equations for estimating glomercular filtration rate GRF are useful for diagnosis of chronic kidney disease CKD. Cystatin is another molecule studied for estimating GFR. Cystatin C is an endogenous marker of renal function; its whole blood levels are not affected by age, sex and nutrition . Serum cystatin C is considered to be a more sensitive marker than creatinine in patients with moderate decrease in GFR 