In Reply to 'External Validation of the Berlin Initiative Study Equations'

摘要

We thank Schaeffner et al1 for their comments. The main limitation of the Berlin Initiative Study 1 (BIS1) equation outlined by our study2 is the variation of the bias with glomerular filtration rate (GFR), which is more of an issue than the inconvenience of implementing a specific equation for elderly patients. This pattern (bias values of +3.95, -0.95, and -11.95 mL/min/1.73 m2 for chronic kidney disease [CKD] stages 4 to 5,3, and 1 to 2, respectively) has been confirmed by 2 other external validations of this equation: Koppe et al3 evidenced median bias of +7.65, +5.1, -1.0, and -3.2 mL/min/1.73 m2 for CKD stages 4 to 5, 3b, 3a, and 1 to 2, respectively, and Alshaer et al4 found median bias of -0.8 and -8.5 mL/min/1.73 m2 for CKD stages 3 to 5 and 1 to 2, respectively.