Discrepancies between the use of MDRD-4 IDMS and CKD-EPI equations, instead of the Cockcroft-Gault equation, in the determination of the dosage of direct oral anticoagulants in patients with non-valvular atrial fibrillation.

Background and Objective: Direct oral anticoagulants (DOACs) require dose adjustment according to estimated clearance creatinine (eClCr) using the Cockcroft-Gault (CG) equation. There are discrepancies with the equations that estimate glomerular filtration rate (eGFR). We analyse how the use of the CKD-EPI and MDRD-4 IDMS equations affect the recommended dosage for ACODs.
Patients and Methods: Retrospective study of patients with non-valvular atrial fibrillation seen at a cardiology clinic between November 2012 and August 2014. Patients were reclassified according to the recommended dosage for dabigatran, rivaroxaban, apixaban and edoxaban, based on the eGFR equation used. Other clinical factors are taken into account, according to the product label. We analysed the percentage of discordance.
Results: Four hundred and fifty-four patients, 53.3% men, with a mean age of 68.7±13.8 years were studied. The mean intra-individual differences recorded for the CG equation were 3.9ml/min/1.73m ² with MDRD-4 IDMS (95% CI 1.4-6.4, P=.003) and 11.3ml/min/1.73m ² with CKD-EPI (95% CI 8.9-13.7, P<.001). A gradient is observed in the discordance of the posology (apixaban 1.1%, dabigatran 3.5%, edoxaban 5.7%, rivaroxaban 8.4% with MDRD-4 IDMS). Differences were limited to patients with eClCr<60ml/min and were more evident in≥75 years in which the eGFR equations overestimate renal function.
Conclusions: In patients with non-valvular atrial fibrillation, especially with renal failure and in the elderly, eGFR equations tend to overestimate renal function relative to CG and therefore suggest an overdose of DOACs.
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