We found that older women with renal dysfunction as defined by mild to moderate reductions in eGFR calculated by the Cockcroft-Gault method are at increased risk of hip fracture. As pointed out in our article,1 it is concerning that we did not find a similar relationship when eGFR was calculated using the abbreviated MDRD equation. As noted by Thorp, potential explanations for this discrepancy include differences in the variation in estimation equations at moderate levels of GFR and issues concerning calibration of serum creatinine measurements with the use of the MDRD equation. Because the creatinine measurements in our study were performed several years ago, we were not able to retrospectively calibrate our creatinine measurements to either the Cleveland Clinic laboratory or the current National Institute of Standards & Technology standard.
Ensrud KE, Ishani A, Taylor BC, Lui L. Glomerular Filtration Rate Results Reflect Estimation—Reply. Arch Intern Med. 2007;167(17):1906. doi:10.1001/archinte.167.17.1906-a