Warfarin Patient Safety Audit: patient data-analysis tool for GP practices
a significantly reduced risk of stroke. Only those with control in excess of over 40% have significantly improved outcomes in terms of overall mortality compared to treatment without warfarin. Results in the summary sheet have recently been altered to now highlight percentage time in TTR using a 65% value, rather than 70%. This change was made to reflect the NICE recommendation that any patient with a TTR below 65% should have anticoagulation reassessed.
Warfarin Patient Safety is an audit tool produced by PRIMIS that is freely available for GP practices in England. Here, the authors explain what is does and how it works. The Warfarin Patient Safety audit tool enables practices to audit their clinical data to look at the appropriateness of warfarin prescribing. In particular, the tool assists in examining whether patients are benefitting from taking warfarin by calculating the amount of time their INR is within therapeutic range (TTR). PRIMIS’ development of the audit tool has been funded by Boehringer Ingelheim Ltd. What does the audit do? The audit tool is concerned with patients who are established on warfarin. It is based on patients who are currently registered at the practice who have had an issue of warfarin both recently (in the last three months) and historically (in the preceding nine months). This produces a cohort that is more relevant for the analyses. The audit tool: n calculates the percentage of time spent in therapeutic range (TTR) from the INRs recorded in the patient’s electronic record n identifies patients with out of range INRs as recommended in the BCSH Guidelines on Oral Anticoagulation1
16 InReview
n calculates the HAS-BLED2 risk score (patients with atrial fibrillation only) and compares it with the patient’s CHA2DS2VASc3 score n reports on patients with or without an identified coded reason for being on warfarin and patients with or without a coded annual warfarin assessment n identifies patients who have had too few or too many INRs over the past 12 months and may therefore be poorly managed How does the audit work? The audit tool works in conjunction with CHART, a software tool also produced by PRIMIS. CHART (Care and Health Analysis in Real Time) is a Microsoft Excel-based program, designed to support GP practices in carrying out clinical audit and data quality reviews. GP practices use the various displays within CHART to review clinical data at both patient and practice level, enabling them to maintain an overall picture of how they are managing patients at a population level but, at the same time, be able to look in detail at the care of individual patients. The Warfarin Patient Safety audit tool produces a practice
Figure 1a: Practice report for the Warfarin Patient Safety audit tool showing that 10 patients have a TTR of less than 40%. A further 55 patients have a TTR between 40-65%.
report summarising the outcome, together with some suggested actions. The results are displayed in a user-friendly format, with easyto-read graphs, tables and an evidence-based narrative.
Figure 1b: The datasheet for the Warfarin Patient Safety audit tool enables practices to easily access and sort the TTRs for each patient included in the audit
Warfarin Patient Safety Audit examples
Out of ranges INR results
Time in Therapeutic Range (TTR)
A patient’s risk of bleeding increases with their INR. The categories reported on in the audit tool are based on specific recommended safety indicators for patients established on anticoagulation. These patients need to be reviewed to see if there is anything which can be done to improve their control:
It is critical that patients prescribed warfarin achieve their desired INR for anticoagulation to be effective. The audit tool uses the Rosendaal4 method to calculate the percentage of time a patient spends within the therapeutic range (TTR). Evidence from a study on patients with AF5 indicates that only patients with a TTR greater than 70% have
n INR above 5 - the risk of bleeding is significantly increased Figure 1a
Percentage time in therapeutic range (TTR) TTR under 40%
TTR 40% - 65%
TTR over 65%
Number of patients
10
55
96
% of all patients with a TTR
6.2
34.2
59.6 Figure 1b
Reference
Age
Sex
Percentage TTR L6M
Percentage TTR L3M
FFBCD3172
85
M
18.9
18.19
BEEDD350
76
F
23.77
23.77
8387F688D
79
F
24.37
24.37