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Warfarin audit in a teaching hospital


Clinical bottom line

Problems in optimal anticoagulant control were manifest, affecting 25 of 100 patients and resulting in 68 extra inpatient days.


J Sowter et al. An audit of warfarin anticoagulation in teaching hospital patients. Pharmaceutical Journal 1997 259:612-613.


Consecutive inpatients on medical and surgical wards in a teaching hospital were identified over a four month period. data on the 100 patients were collected using a standard form. The nurse in charge of the ward determined whether any delay in discharge occurred solely because of failure to attain optimal anticoagulation.


The 100 patients were aged 19 to 97 years (mean 64 years), and were in hospital for 1369 days (mean 14 days). They had 1065 INR tests in the 1369 days they were in hospital. No pre-warfarin INR baseline was measured in 37 of them.

The number of days taken to attain the target INR is shown in Figure 1. Sixteen patients had not attained the target by time of discharge.

Figure 1: Days of warfarin treatment before target INR achieved.

Difficulty in achieving optimal anticoagulation was the sole cause of discharge delay in 25 patients, resulting in 68 extra days spent in hospital (5% of total bed days for these 100 patients).


This simple audit revealed a number of problems. These included the absence of pre-treatment INR, problems with initial warfarin dose decisions, and drug interactions. Recognising the problem led to changes in organisation and management, and moves to improve the initial choice of warfarin dose.