Non-vitamin K antagonist oral anticoagulants (NOACs) are increasingly being used for the prophylaxis of stroke in patients with non-valvular atrial fibrillation (NVAF). One of their limitations is their reliance on renal clearance making them potentially more unsafe in patients with renal impairment. NICE recommend regular renal function testing in these patients as well as drug dose adjustments to be made according to their calculated CrCl.
Aims 1. To identify patients with NVAF who have been prescribed NOACs and to measure the percentage of those that have had renal function tests done in the last 12 months.
2. To determine if patients are being prescribed the correct anticoagulant dose as per their CrCl?
3. Are 100% of patients having their renal function and weight monitored at the correct frequency according to NICE recommendations?
Methods Data was collected from two GP practices in Bognor Regis. CrCl was calculated for each patient by using the Cockgroft-Gault equation. The dose of anticoagulant was then reviewed for each patient to see if it was appropriate as per their CrCl.
Results 176 patients were identified. 45% of patients were prescribed Apixiban, 41% were prescribed Rivaroxaban and 14% of patients prescribed Dabigatran.
The average age of patients was 77 years old with a median age group of 78 years.
84.5% of patients on NOACs had their renal function tested in the last 12 months with the remainder of patients having their renal function monitored at varying time periods greater than 12 months and less than 3 years. It was found that one patient had no record of their renal function.
In order to calculate their CrCl, weight measurement is also required. However only 49% of patients had their weights checked in the last 12 months. 4% of patients had no recorded weights.
Accurate CrCls could only be measured in 46% (81/176) of patients, of whom had both renal function and weights recorded in the last 12 months.
Assuming stable weights, all patients prescribed apixiban and dabigatran were prescribed the correct dose as per their CrCl, however only 81% (59/73) of patients taking rivaroxban were on the correct dose. 2 patients were under anticoagulated despite normal CrCl, and 12 patients despite having impaired renal function (CrCl<50) were prescribed the higher dose. Patients with impaired renal function (CrCl<60) did not have their renal function monitored more frequently as is suggested by NICE.
Summary Whilst the majority of patients have had their renal function tested in the last 12 months, a significant number are not having their weight checked. Accurate dosing of the NOACs therefore cannot be done as creatinine clearances are not being accurately measured. Incorrect dosing increases risks of adverse events such as bleeding. Findings from this study were presented at the two GP surgeries during practice meetings to raise awareness of the problem and incorrect doses were rectified.
- atrial fibrillation
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