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Qualitative Measures: Point Prevalence Surveys (PPS)

This article introduces Point Prevalence Surveys (PPS), including their benefits and limitations.

AMS interventions can be monitored in various ways, including by quantity, structural measures, processes and patient outcomes. We have already looked at some quantitative measures (DDD and DOT), but sometimes qualitative data can be more valuable.

By now, you will be familiar with the idea of auditing. Auditing is the key method of collecting qualitative data with antimicrobial stewardship programmes. Audits may be carried out in a variety of ways depending on resources available and objectives for collecting them.

Some types of qualitative measurement include:

Continuous audit: data on all patients prescribed antibiotics. Rarely practical without electronic data systems.

Point prevalence surveys (PPS): snapshot audits across the whole hospital or selected wards at regular time intervals to track trends.

Prescribing indicators: collection of selected data to provide information about specific aspects of prescribing practice.

In this step, we will be focusing on PPS.

Methods to understand the problem areas

Point prevalence surveys are a systematic and structured way to collect data about how antimicrobials are used. They are snapshot audits across a whole hospital or selected wards, made at regular intervals to track trends and show the number of people taking antimicrobials at a given point in time. The image below offers a summary of the 5 potential benefits or uses of a health care facility PPS.

List of the 5 potential benefits or uses of a health care facility PPS.

The diagram below illustrates information that could be collected to help understand problem areas.

What is a PPS?

Point prevalence can be defined as the number of people with a particular characteristic at a certain point in time. The diagram below shows how you can calculate the point prevalence.

Example equation showing how to calculate point prevalence

A point prevalence survey is often used in healthcare to determine the prevalence of an infection. A PPS of antibiotic use will measure the number of people taking antibiotics at a given time within a hospital or ward.

An example of a PPS could be as follows:

  • A ‘one day’ cross sectional PPS reviews each ward within a hospital on a single day.
  • The PPS only reviews antimicrobial prescribing and resistance.
  • The survey sets out to answer the question “who is taking antibiotics?”
  • It achieves this by asking patients taking antibiotics to fill out a questionnaire that asks:
  1. What antibiotic are you taking? At what dose? For how long?
  2. Is this for treatment or prevention?
  3. What infection is the antibiotic for?
  4. Have you been given proper prescription guidelines?
  5. Were diagnostic tests performed before prescription?

Benefits of a point prevalence survey

Below we highlight the range of uses from the information accrued from a PPS. A PPS is a very valuable tool to inform and guide AMS interventions as well as measure the progress or impact of AMS interventions.

PPS can be used to identify and monitor:

  • Antimicrobial prescribing in hospitalised patients.
  • Differences in prescribing rates and quality – useful for comparing departments, hospitals, regions and countries.
  • Use of broad or narrow spectrum antibiotics.
  • Variation in antibiotic, dose and indication across different locations.

Data can inform:

  • Community or hospital acquired infections, medical or surgical prophylaxis.
  • Which antibiotics are being used to treat which infections.
  • Whether antibiotics are being prescribed in accordance with local guidelines.
  • The duration of antibiotic use in surgical prophylaxis.
  • Whether a stop date has been recorded.
  • If the treatment has changed after considering microbiology results.

Used more broadly, the data can:

  • Inform local benchmarking and quality improvement.
  • Be used for internal scrutiny or target-setting.
  • Be used for external quality assurance.
  • Provide stewardship evidence and indicators for hospital managers.
  • Provide evidence for financial incentives or penalty avoidance.
  • Be used in research or audit purposes.

Evidence to support AMS quality indicators

In this section, we will explore some key evidence to support the use of AMS quality indicators.

This 2017 systematic review by Kallen et al., highlights commonly developed indicators for appropriate antibiotic use in hospitalised adult patients.

Point prevalence surveys conducted in series over time can highlight quality improvements as AMS interventions take effect. This 2013 study by Malcom et al. provides a very good example of how data from a national PPS led to the creation of national hospital indicators for antibiotic prescribing which were subsequently re-audited through further point prevalence surveys.

timeline showing progress from PPS to continued quality improvement, and a table of data from the Malcom et al. study.

Click here to see a larger version of this image.

This 2015 article is a very good example of China introducing national qualitative and quantitative measures or indicators as targets for prescribing in the outpatient and hospital setting. The creation of indicators or metrics for targets is an example of measures being used for scrutiny or judgement.

How do you actually perform a PPS?

The WHO toolkit (chapter 4.7) provides a clear methodology for setting up a PPS in a healthcare facility, as shown below.

This infographic is also available as a screen-reader compatible PDF.

Doing a PPS can be relatively simple! Below is a pragmatic approach that identifies who does what, where, what is needed, how the data is collected, collated, analysed and communicated and the importance of information governance.

This infographic is also available as a screen-reader compatible PDF.

Data collection in a PPS

While it is useful to have an IT system such as a spreadsheet for recording, the information can be collected on paper on a ward and then aggregated. A simple data collection form is shown below.

Simple example data collection form

Another example of a data collection form from Ireland can be found in this 2014 report. This report highlights core data being collected in a PPS form. The ESAC methodology significantly influenced the WHO PPS methodology.

This 2018 study by Versporten et al. is an example of a form for collecting denominator data (how many patients on the ward and beds on the ward at 0800). IT systems are usually a challenge and not widely available in LMICs- the use of paper forms are widely used tools for collecting data. It outlines that YOU DO NOT need IT systems to do simple point prevalence surveys. The key issue is uniformity of data collection, a collective common understanding of definitions and what is being collected and ensuring that the data are verified.

To learn more about PPS, look at this FututreLearn course which will teach you how to use Point Prevalence Surveys (PPS) to measure antibiotic consumption and fight antimicrobial resistance.

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How to set up an Antimicrobial Stewardship Programme

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