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Home / Healthcare & Medicine / Antimicrobial & Antibiotic Resistance / Antimicrobial Stewardship for the Gulf, Middle East and North Africa / Measurement of Antibiotic Consumption

Measurement of Antibiotic Consumption

Learn more about measurement of quantity and quality of antibiotic consumption.
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Hello. My name in Arabic is Khalid Eljaaly - in English, Khalid Eljaaly. I am an infectious disease and antibiotic stewardship pharmacist. And I will be talking about measurement of antibiotic consumption. There are several methods for measuring the quality of antibiotic prescribing and interventions, by the antibiotic stewardship programme and healthcare professionals. Without electronic prescribing, one relatively easy way to measure quality is by using point prevalence survey, PPS. PPS is a snapshot to collect information about prescribed antibiotics and interventions. It can identify targets for quality improvement of prescribing. And it can be used to enhance awareness of health care professionals.
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It should be done regularly to monitor antibiotic prescribing and adherence to several interventions if this can be adjusted based on the targeted intervention. You can follow the link, www.global-pps.com in the text underneath this video for more information. After we identify targets for improvement, how can we prioritise targets for improvement? One way is to follow the model for improvement, which was developed by the Institute for Healthcare Improvement. Three questions need to be answered. What are we trying to accomplish? How will we know that a change is an improvement? What changes we can test that will result in an improvement?
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Quality measures can be divided into three types: structural, process, and outcomes. Let’s look at these more closely. Structural measures evaluate whether governance structures are in place for the antibiotic stewardship programme, such as the availability of formal antibiotic stewardship team, meeting regularly, and inclusion of certain staff into the stewardship team.
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Process measures evaluate the systems in place for the programme, such as percentage of adherence to a documentation policy, intervention, or guideline, and percentage of recommendation acceptance. Finally, examples of outcomes measures are clinical cure, mortality, length of stay, C. diff infections, and antibiotic resistance. They should include both intended outcomes, such as reduce resistance to reserved antibiotics, and unintended outcomes, such as increased resistance to recommended antibiotics. Quantity measures evaluate aggregate antibiotic use. They are the most common measures of antibiotic stewardship programme. Antibiotic quantity can be compared over time and across locations. The preferred numerators for measuring antibiotic quality are defined daily doses (DDDs), and days of therapy (DOT).
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Examples of other quantity measures are prescribed daily dose, length of therapy, number of tablets, and number of prescriptions. I will focus on DDD and DOT and the differences between them. The DDD is the number of grams dispensed divided by the WHO DDD. The WHO DDD is the assumed average maintenance dose per day for a drug use in its main indication in adults. I will show you how to get this WHO DDD. You can go to the website for the WHO ATC DDD index. There will be a link in the text below. On this page, you can search for the antibiotic by entering its name or code. If you type ciprofloxacin, you will see different ciprofloxacin forms.
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The code J is for systemic use. And if you click the first option, we will get the WHO DDD for systemic ciprofloxacin, which as you can see, is 0.8 for parental use, since the typical dose is 0.4 grams q 12 hour. And one for oral use, since the typical dose is 0.5 grams q 12 hour. Let’s take an example to understand how to calculate the DDD for ciprofloxacin.
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If at a certain period a hospital used 800 vials and 3,000 tablets of ciprofloxacin, the ciprofloxacin DDD for vials would be number of vials, which is 800, divided by the WHO DDD, which is 0.8, which equals 1,000, while the ciprofloxacin DDD for tablets would be number of tablets, 3,000, divided by the WHO DDD, 1, which equals 3,000. Then we can combine the DDD for all formulations to get the total DDDs for ciprofloxacin. Using DDD has some advantages and disadvantages, advantages include that it is published by WHO, and well-known internationally. It is updated annually. A big advantage is it doesn’t require patient-level data. It is easy to have antibiotic use information for a ward unit, or a hospital.
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Disadvantages include that DDD might change. It is based on a standardised dose, not a prescribed dose. Loading doses are not accounted for. DDD correction factor by WHO is debatable. We need to consider changes in dosing recommendations. DDD is inappropriate for children, and underestimates use in renally impaired patients, while it overestimates use in indications requiring higher doses or longer durations. We have to be careful, because combination products might be based on one constituent. For example, with piperacillin-tazobactam, WHO DDD refers to piperacillin only. Now let’s discuss days of therapy, DOT. It is different than length of therapy, which is the number of days a patient receives any antimicrobial.
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While DOT is the number of days a single antimicrobial is administered, regardless of the number of doses administered or dose strength. For example, if a parent received both cefepime and vancomycin for two days, the length of therapy is two days, while the DOT is four days, because it was two days of cefepime plus two days of vancomycin. The advantages of DOT are that it is recommended in the US by CDC National Health Safety Network, and guidelines by Infectious Disease Society of America, and Society for Healthcare Epidemiology of America. Unlike DDD, it’s not affected by different dosing recommendations or percent of renally impaired patients. And it can be used in paediatrics.
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The main disadvantage is that it requires patient level information, and so is more difficult to measure without electronic records. For quantity measures, it is important to divide it by a denominator which might include all patients, not just those who received antimicrobials. The denominator accounts for fluctuations in hospital activity, such as the number of patients in hospital and the length of stay, and enables consumption measurement over time and between hospitals.
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Examples of denominators are: number of patient days, occupied bed days, admissions, and days present.
Dr Khalid Eljaaly describes how there are several methods for measuring the quality of antibiotic prescribing and interventions by the antibiotic stewardship program and health care professionals.

Without electronic prescribing, one relatively easy way to measure quality is by using Point Prevalence Survey (PPS).

One way to prioritise targets for improvement is to follow the Model for Improvement. Three questions need to be answered:

  • What are we trying to accomplish?
  • How will we know that a change is an improvement?
  • What changes we can test that will result in an improvement?

Quality Measures

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This content is taken from
BSAC online course,

Antimicrobial Stewardship for the Gulf, Middle East and North Africa

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Structural Measures evaluate whether governance structures are in place for the antibiotic stewardship program such as availability of formal stewardship team, meeting regularly, and inclusion of certain staff into the stewardship team.

Process Measures evaluate systems in place for the program such as percentage of adherence to a documentation policy, intervention, or guideline, and percentage of recommendation acceptance.

Examples of Outcomes Measures are clinical cure, mortality, length of stay, C. difficile infections, and antibiotic resistance.

Quantitative Measures

The preferred numerators for measuring antibiotic quantity are defined daily doses (DDDs) and days of therapy (DOT). Examples of other quantitative measures are prescribed daily dose, length of therapy, number of tablets, and number of prescriptions.

DDD is the number of grams dispensed divided by the WHO DDD. The WHO DDD is the assumed average maintenance dose per day for a drug used in its main indication in adults.

WHO ATC/DDD Index

The DDD should be differentiated from another metric called prescribed daily dose (PDD), which is the average dose prescribed according to a representative sample of prescriptions. The PDD can be calculated from studies of prescriptions or medical or pharmacy records. PDD should be related to the indication for which the antibiotic is prescribed. The number of prescriptions and physical units (e.g., grams) can be used too and are easy to obtain.

DOT is the number of days a single antimicrobial is administered regardless of the number of doses administered or dosage strength.

DDDs are discussed further in the Antimicrobial Stewardship: Managing Antibiotic Resistance FutureLearn course. BSAC also has a course on Point Prevalence Surveys which provides further detail on their use and practical guidelines.

Do you currently carry out any quantitative measures of antibiotic consumption in your healthcare setting?

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This content is taken from BSAC online course
Antimicrobial Stewardship for the Gulf, Middle East and North Africa
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