The calculation written in 1976 known as the Cockcroft and Gault method used both serum creatinine and body weight to estimate creatinine clearance. This was followed in 1999 by the 6 variable Modification of Diet in Renal Disease (MDRD) which utilizes a patient's serum creatinine, BUN, albumin as well as age, gender and race to calculate the GFR and the 4 variable in 2000 which only used age, serum creatinine, gender and race.

Note that both of these equations do not include patient's weight and are assumed to be standardized to a body surface area of 1.73. From personal experience patients with large body mass tend to have calculated values for Gault and MDRD that very greatly and this can cause a dilemma especially in dosing medications. I have included a version of the MDRD formula's labeled MDRD* which utilizes the patients BSA to correct for differences of body size. Please see the form labeled MDRD* for more information.

This GFR calculating software which I wrote utilizes both MDRD formulas as well as one that calculates GFR from age, gender, race, serum creatinine and BUN and a creatinine clearance calculator from a spot (or timed) urine and the amount of urine made in 24 hours. The results are listed as GFR by MDRD, Gault, creatinine clearance, MDRD*, average of these methods, % of GFR expected for age, Stage of CRI, and expected GFR for age.

The user can select which methods to be used in his/her calculations for the average GFR with the default values being MDRD and Gault. The software automatically stores your selection choices for further use. As a general rule I always enter the patients' weight to get a value by the Gault-Cockcroft method especially in patients with a BSA that differs greatly from 1.73 square meters. If the patient's height and weight is entered the BSA is displayed on the results form.