*The Cockcroft formula can also be expressed per 1.73 m2 body surface area.
†The original MDRD equations were validated with the modified kinetic Jaffe method used to assess creatinine. Because this commonly used assay overestimates creatinine, a different prediction equation has to be used when the (more expensive) enzymatic assay traceable to the reference method GC-IDMS is used to assess creatinine. GFR can be estimated easily using MDRD available online; for example, see http://www.mdrd.com