Performance of simplified modification of diet in renal disease and Cockcroft-Gault equations in patients with chronic spinal cord injury and chronic kidney disease.
BACKGROUND
The purpose of the study was to compare the performance of the simplified Modification of Diet in Renal Disease (MDRD) and Cockcroft-Gault (CG) equations with 24-hour urinary creatinine clearance (Ccr) in patients with spinal cord injury (SCI) and chronic kidney disease.


METHODS
A retrospective diagnostic accuracy study of 116 patients with chronic SCI followed at the Memphis Veterans Affairs Medical Center Spinal Cord Injury Unit with measured Ccr (mCcr) <90 mL/min/1.73 m.


RESULTS
Linear regression analysis relating estimated glomerular filtration rate (eGFR) to mCcr showed a highly significant correlation between mCcr and eGFR (n = 116; r = 0.81, r = 0.65, P < 0.0001); however, the relationship was more variable in the quadriplegic subjects (n = 52; r = 0.74, r = 0.54, P < 0.0001) than in the paraplegic subjects (n = 64; r = 0.86, r = 0.73, P < 0.0001). Both eGFR equations overestimated glomerular filtration rate (GFR) at all ranges of GFR in both subgroups of paraplegic subjects and quadriplegic subjects, with an MDRD fractional prediction error of 49% and 62%, respectively. Addition of a correction factor of 0.7 for MDRD and 0.8 for CG equations resulted in clinically acceptable fractional prediction error (below 20%) in both subgroups, especially in paraplegics with 3.9% and 3.6%, respectively. There was marked improvement in the performances of both eGFR equations, with better accuracy and precision after application of the correction factors.


CONCLUSIONS
Both MDRD and CG equations overestimate GFR in patients with chronic SCI at all stages of chronic kidney disease, particularly in quadriplegic subjects. An empirically derived correction factor markedly improved the performance and accuracy of both prediction equations.
Chikkalingaiah
Kiran B M
KB
Veterans Affairs Medical Center, Internal Medicine Department, The University of Tennessee Health Sciences Center, Memphis, USA.
Grant
Natarsha D
ND
Mangold
Theresa M
TM
Cooke
C Robert
CR
Wall
Barry M
BM
D015982:Bias; D003404:Creatinine / Q000097:blood / Q000378:metabolism; D004032:Diet; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D007676:Kidney Failure, Chronic / Q000178:diet therapy*; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D013119:Spinal Cord Injuries / Q000178:diet therapy*
D003404:Creatinine