MDRD GFR calculator Formula:
   GFR = 186.3 x c^-1.154 x a^-0.203 x 1.212(if black) x 0.742 (if female)
Where:
   mdrd: Glomerular Filtration Rate, in ml/min/1.73m²
   c: Serum Creatinine, in mg/dL
   a: in years