Accuracy of formula-derived creatinine clearance in paraplegic subjects

The usefulness of formula-derived creatinine clearance (CC) is not well established among the paraplegic population. We prospectively collected 24-hour-urines from paraplegic subjects, obtaining 81 collections from 42 patients over 27 months. After validation, 57 collections were used to obtain measured CC. CCs were also estimated using several formulae. Measured CC and estimated CC were then compared. In the case of the Cockroft-Gault formula, the overall correlation was excellent, with an r value of 0.88 and p = 0.0001. In our study 40, 70, and 93% of the estimated CCs were within 10, 20, and 33% of the measured CCs. These numbers are similar to the ones reported by Cockroft and Gault. Also, the data on measured creatinine clearance in paraplegics compared favorably with parallel data obtained from nonparaplegics (91 24-hour-urine collections, 65 validated). We conclude that the Cockroft-Gault formula (and other formulae) estimate creatinine clearance as accurately in the paraplegic population as they do in the nonparaplegic population.