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What about the denominator?

What about the denominator?
5.4
So far we’ve considered the way to measure antibiotic use using DDDs, but that may be only part of the story. It’s always important, you must always look at the raw DDDs in order to get a sense of whether it is increasing, decreasing, or staying the same. But of course changes in the patient census may account for some of any differences that you are observing. So it is important that you choose a denominator to allow you to make a much more meaningful comparison over time, or indeed between different areas. So that could be between different wards in your hospital, between different directorates in your hospital, or even between hospitals in your area. Or perhaps even between countries.
48.2
So it’s important to normalise antibiotic prescribing and to a rate in order to take account of any changes in hospital activity such as a number of patients admitted or their length of stay. So what are the options? Perhaps the most commonly used option is the number of patient days or occupied bed days. The landmark guidance on antimicrobial stewardship produced by the Infectious Disease Society of America recommended the metric of DDDs per 1,000 patient days as a way to monitor antimicrobial stewardship in hospitals. So as you consider whether you can use a denominator, ask yourself how easy would it be for you to access this type of bed utilisation data for your hospital.

Now watch this very short video clip on the importance of choosing an appropriate denominator.

So far we have considered the way to measure the volume of antibiotic use, but that may only be part of the story. It is always helpful to review the raw DDD data to get an indication of whether it is changing over time.

Changes in patient census in the hospital may account for some of any differences observed. A denominator will be needed to enable the measurement of use over time and between hospitals become meaningful. Normalising antibiotic use and presenting it as a rate will help account for fluctuations in hospital activity such as the number of patients in hospital and their length of stay.

So what are the options?

One of the most commonly used denominators in hospital stewardship programmes is the number of patient days or occupied bed days. This requires information on bed utilisation.

The landmark guidance on antimicrobial stewardship by the Infectious Disease Society of America and Society for Healthcare Epidemiology of America recommends DDD/1000 patient days as a metric for hospital based antimicrobial stewardship programmes.

As you consider denominators ask yourself if you can access this type of hospital activity data for your own hospital.

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Antimicrobial Stewardship: Managing Antibiotic Resistance

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