National Health Survey: Persons accessing Pharmaceutical Benefits Scheme subsidised prescriptions, 2014-15

This research paper showcases the integration of the 2014-15 National Health Survey (NHS) with the Multi-Agency Data Integration Project (MADIP) asset. The MADIP asset includes data from the Pharmaceutical Benefits Scheme (PBS) which funds access to the supply of medications via subsidised prescriptions through the PBS and the Repatriation Pharmaceutical Benefits Scheme (RPBS) by the Australian Government. The analysis presented assesses the feasibility of using data from the PBS represented in the MADIP asset to replace the medications questionnaire module in future NHS cycles, and explores the use of PBS subsidised prescriptions by participants in the linked 2014-15 NHS dataset.

The NHS is an Australia-wide health survey conducted by the Australian Bureau of Statistics (ABS) which collects information about the health of people, including: 

• prevalence of long-term health conditions
• health risk factors such as smoking, overweight and obesity, alcohol consumption and physical activity
• demographic and socioeconomic characteristics
• health related actions such as medication use.

MADIP is a partnership among Australian Government agencies to develop a secure and enduring approach for combining information on healthcare, education, government payments, personal income tax, and population demographics (including the Census) to create a comprehensive picture of Australia over time.

The 2014-15 NHS is the first ABS household survey to be linked to the MADIP asset and provides the opportunity to explore, investigate and better understand relationships between health status as measured in the NHS and use of government services. For more information regarding the integration of the 2014-15 NHS with the MADIP asset, see: 4321.0 - Research Paper: Integration of the National Health Survey with the Multi-Agency Data Integration Project (MADIP), 2014-15.

The ABS is making more use of administrative data to help inform policy decisions and research questions. Using administrative data has many advantages compared with collecting data through surveys including: reducing respondent burden; minimising respondent recall bias; and reducing costs. The ABS uses supermarket scanner data to improve the processing of the Consumer Price Index, tax data to support business collections, and more recently has explored opportunities to replace some household survey questions with existing administrative data from the MADIP.

One such example is covered in this research paper, where the ABS proposes to replace the direct collection of medications information with the PBS subsidised prescriptions data in the MADIP asset.

The 2014-15 NHS was conducted in all states and territories and across urban, rural and remote areas of Australia from July 2014 to June 2015. The survey included 19,257 people in 14,723 private dwellings.

Results in this research paper are based on the 18,287 2014-15 NHS records that were linked to the MADIP asset (a linkage rate of 95%). The linked records have been re-weighted to represent the population estimates of the NHS representing approximately 23 million people in Australia in 2014-15. For more information on weighting, see the Explanatory Notes.

As the scope of the 2014-15 NHS excluded very remote areas and discrete Aboriginal and Torres Strait Islander communities, there is no coverage of these populations in the linked dataset.

For the linked records, the analysis presented in this paper is based on PBS subsidised prescriptions for the 12 months prior to the NHS interview. PBS subsidised prescriptions are included based on the date of supply that a subsidised prescription medicine was filled at a Pharmacy. As a result, PBS records used have supply dates ranging from approximately July 2013 to June 2015. The 12 month data period allows for the analysis of patterns of medication use.

There are a number of factors that should be considered when interpreting information presented in this research paper.

Self-reported medication use was collected in the medications questionnaire module of the 2014-15 NHS and it is important to note the following:

• All medication use is captured in a face-to-face interview and represent medications used in the two weeks prior to interview.
• Medication use was self-reported by respondents, which may have implications for the extent to which certain types of medication were reported.
• Whilst respondents were encouraged to collect their medications to assist in recall, this did not always occur, which may have led to some medications not being reported, or being reported incorrectly.
• Some respondents may have provided responses that they felt were expected, rather than those that accurately reflected their own situation. Every effort has been made to minimise such bias through the development and use of appropriate survey methodology.
• Interviewers recorded the Australian Register of Therapeutic Goods Administration (TGA) identification number of each medication taken by the respondent. These were either:
  • AUST R medicines - which include all prescription medications and many over-the-counter products such as those used for pain relief, coughs and colds and antiseptic creams; or
  • AUST L medicines - which are generally lower risk self-medication products which include vitamins, minerals, and herbal and homoeopathic products.
• A small number of medications presented by respondents were not able to be coded to the World Health Organisation Anatomical Therapeutic Chemical (ATC) classification system[1], and were not included in output data. For example, for medications containing multiple active ingredients, or medications containing ingredients used for more than one therapeutic application. This is expected to have negligible effect on the accuracy of results.
• Information on what the medication was being taken for or prescribed for is not captured.
• For further information on the 2014-15 NHS, refer to the Explanatory Notes and User Guide.
   

For PBS subsidised prescriptions represented in the MADIP asset, it is important to note the following:

• The Scheme is available to all Australian residents who hold a current Medicare card. For certain countries, the Australian Government’s Reciprocal Health Care Agreement (RHCA) allows international visitors to access PBS subsidised prescriptions.
• The subsidy of some prescriptions is restricted to particular population or clinical subgroups which may impact on the representation of the data available.
• There are programs operating under Section 100 of the National Health Act 1953 particularly in remote and very remote areas, such as the Aboriginal Medical Services, which receive access to free and subsidised medicines, at times on a bulk supply basis, that are not captured through the PBS data when distributed to patients[2].
• PBS subsidised prescriptions can be identified based on timeframes using the prescription supply date.
• PBS subsidised prescriptions do not include over-the-counter, private prescriptions, dietary supplements or medications supplied to public hospital in-patients.
• Some prescription medications are not captured through PBS data, these are referred to as non-PBS prescriptions. Examples include prescription medicines that are not listed on the PBS and medications that are being used outside of its PBS manner of administration (such as PBS eye ointment for topical non-ophthalmic use)[3].
• PBS subsidised prescriptions tell us when a prescription is filled but not whether the patients took the medication.
• The ABS update the MADIP asset on an annual basis with data on the PBS received from Services Australia. The MADIP asset (at the time of this research) contained PBS subsidised prescriptions from 2011 to 2016.

For more information on the MADIP asset, refer to the ABS MADIP webpages.

Self-reported medication use in the 2014-15 NHS and PBS subsidised prescriptions have the following in common:

• A person’s use of medication(s) does not imply a diagnosis of a condition.
• It is not known whether people actually used the medications they self-reported in the 2014-15 NHS or the medications for which subsidised prescriptions were filled in the PBS.
   

There are three types of medications available in Australia[4]. These are:

• Complementary: non-prescription medicines available predominantly over the counter from health food shops, supermarkets and pharmacies.
• Over-the-counter: non-prescription medicines available over the counter or accessible from a pharmacist after a consultation. These medicines are available in pharmacies with selected products also available in supermarkets, health food stores and other retailers. Such medicines are typically used for mild health problems.
• Prescription: medicines that can only be accessed via written instruction of an authorised health professional, for example a General Practitioner. These medicines are only available for purchase from a pharmacy.

All medicines in Australia must be either registered or listed with the Australian Register of Therapeutic Goods (ARTG). All prescription medicines in Australia are registered as they carry higher risks when consumed, thus requiring a valid prescription from a health professional to gain access. The Australian Government subsidises the access to prescription medication through the PBS and RPBS, and it is such medicines that are represented in the MADIP asset.

Over-the-counter and Complementary medications are either register or listed, but can be accessed off the shelf (some requiring a discussion with a Pharmacist) as they carry lower risk upon consumption. When purchased off the shelf without a prescription these medicines are not subsidised through the PBS or RPBS and are not represented in the MADIP asset.

This section compares the self-reported medication use data from the 2014-15 NHS to the PBS subsidised prescriptions data represented in the MADIP asset to determine the suitability of replacing the medications questions module in future NHS cycles with the rich PBS administration data source.

To compare the two data sources, comparability of reference periods was explored. The self-reported medications use data from the 2014-15 NHS represents medications used in the two weeks prior to the NHS interview. Using the supply date which represents when a PBS subsidised prescription was filled at a pharmacy, PBS subsidised prescriptions were categorised into two time periods representing:

• PBS subsidised prescriptions filled in the month of or month prior to interview (referred to as month prior to 2014-15 NHS interview)
• PBS subsidised prescriptions filled up to 12 months prior to interview (referred to as 12 months prior to 2014-15 NHS interview).

These categories were chosen because the PBS supply date available in MADIP is represented only by month and year, meaning data comparisons could not be made specifically for the two weeks prior to the 2014-15 NHS interview. The 12 month prior period was of interest to consider for medicine use for long-term health conditions.

Of the linked 2014-15 NHS population, there was generally more people self-reporting medication use compared with people who had at least one script filled for a PBS subsidised prescription in the month prior to the NHS interview (46.7% compared with 41.6%). Greater similarity can be observed between the 2014-15 NHS and PBS subsidised prescriptions typically for ATC Classification System groups where medications are only available via prescription for example, Cardiovascular system (18.0% compared with 17.8% respectively). However, this pattern is not evident across all of the ATC Classification Systems groups and is particularly inconsistent where over-the-counter medications are typically used, for example, Blood and blood forming organs (7.5% compared with 3.9% respectively) see Table 1 below.

As expected, when the 2014-15 NHS two week self-reported medication use was compared to the PBS subsidised prescriptions filled up to 12 months prior to the 2014-15 NHS interview, a greater difference between the two data sources was observed for most ATC groups. However, where over-the-counter medications are readily used (for example, for Blood and blood forming organs, Respiratory system and Nervous System groups where aspirin, Ventolin, pain relief and cold medications are respectively used) the same pattern does not hold.

For information on over-the-counter and prescription medications in Australia, please refer to the Interpretation of results section.

To assess the impact of replacing the NHS medications questionnaire module with PBS subsidised prescriptions available via the MADIP asset, a proportion agreement between the two data sources was calculated as follows. The proportion agreement uses the frequency of agreements and disagreements observed for the linked records which have the presence (or non-presence) of a self-reported or PBS accessed medication in the month prior to interview, in a particular ATC group (i.e. a binary categorical variable).
 

Although test statistics such as Cohen’s ĸ could be used to statistically test the level of agreement between the two datasets, such statistics have several limitations, including difficulty of interpretation[5] therefore the decision was made to report proportion agreement, which is directly interpretable.

The proportion agreement was calculated for each ATC Classification System group (see Table 2). High levels of agreement were achieved for most ATC Classification System groups when comparing self-reported medication use from the 2014-15 NHS to the PBS subsidised prescriptions represented in the MADIP asset.

Like the raw proportion comparisons in Table 1, levels of agreement were not as strong for ATC Classification System groups where over-the-counter medications are readily used, such as the Nervous system group.

Caution should be used when interpreting the level of agreement for the various ATC Classification System groups, as groups with a very small proportion of usage will inherently have a high proportion agreement. The proportion agreement should be viewed in conjunction with Table 1 to assess the overall comparability of the two data sources.

Generally, results showed a higher level of agreement between self‐report and prescription based data for medications used on a regular and ongoing basis (for example, for treatment of chronic conditions such as heart disease). In contrast, the difference between the two data sources for some medications may be explained, to a greater or lesser extent, by their availability over-the-counter and also, those medications that are used intermittently, infrequently or on a short-term basis (such as the use of antibiotics for acute infections). There have been similar results found in other research studies comparing self-reported and prescription data sources[6,7].

Overall, the linkage between the 2014-15 NHS and the PBS subsidised prescriptions as represented in the MADIP asset appears feasible to replace the survey data. For ATC Classification Groups where over-the-counter medications are commonly used, data could possibly be supplemented through specifically asking about the use of key over-the-counter medications in the survey.

Replacing survey content with the PBS subsidised prescriptions would help improve survey efficiency in future NHS collections. Whilst the PBS was not designed for research or planning purposes, the data are an objective and accurate record of medicines that were supplied and when they were supplied. Both data sources have pros and cons, but when taking into account the availability of existing data sources and respondent burden it appears feasible to use administrative data where possible as a survey data replacement. The ABS will endeavour to investigate whether additional administrative data sources exist that would help address over-the-counter medications, private prescriptions, dietary supplements and other data gaps.

After comparing time windows, it would be preferable to replace the NHS medications questionnaire module with PBS subsidised prescriptions as close to the survey reference period as possible. However, when analysing PBS subsidised prescriptions use, a longer time period would allow for more analysis of the patterns of medication use.

This section explores the linked dataset from the integration between the 2014-15 NHS and the MADIP asset. It presents data on the use of PBS subsidised prescriptions by certain characteristics of people in the 2014-15 NHS.

Data is presented across a range of medications according to the World Health Organization Anatomical Therapeutic Chemical (ATC) Classification System[8]. It is a classification system that classifies the active ingredients of medications according to the organ or system on which they act and their therapeutic, pharmacological and chemical properties. The ATC Classification System categorises medicines into one of fourteen anatomical groups, which are presented in this research paper.

For the 12 months prior to the 2014-15 NHS interview:

• Seven in ten (70.5%) people had at least one script filled for a PBS subsidised prescription.
• Antiinfectives for systemic use, which include antibiotics, were the most commonly accessed type of medication, with almost half (45.5%) of all people having at least one script filled.
• Nervous system medications, which include mental health and psychoactive related medications, were the second most commonly prescribed medications. Just over one quarter (26.2%) of all people accessing at least one PBS subsidised prescription for this medication type.
• On average, the highest number of scripts filled per person was for Cardiovascular system medications with an average of 18.5 scripts per person.

In terms of age, older people were more likely to access PBS subsidised prescriptions, which could be attributed to factors such as increasing life expectancy, prevalence of conditions and polypharmacy.

Of all people in the NHS who accessed at least one PBS subsidised prescription up to 12 months prior to their 2014-15 NHS interview:

• Females (75.9%) were more likely than males (65.0%), to access at least one PBS prescription medication.
• Generally, access to PBS subsidised prescriptions increased with age. The majority of people aged 75 years and over (97.8%) accessed at least one PBS subsidised prescription.
• The largest difference between females and males by age group was at 18-24 years (81.4% compared with 49.5% respectively). This difference generally reflects females’ gynaecological and reproductive health needs.
   

Across most age groups for males and females, Antiinfectives for systemic use medications were the most commonly accessed subsidised prescription in the linked dataset. However, the relative pattern of use for males and females differed across age, particularly in adults aged 18-44 years. The rate did not necessarily increase with age, as typically observed in other ATC medication groups.

Antiinfectives for systemic use medications include antibiotics which help stop infections that are caused by bacteria. Australia has a relatively higher rate of antibiotic prescribing compared with the Organisation for Economic Co-operation and Development (OECD) average (23.4 per 1,000 people, compared with an OECD average of 20.6 per 1,000 people)[9].

Nervous system medications were the second most commonly accessed subsidised prescription in the linked dataset and include antipsychotics, anxiolytics/hypnotics and sedatives, antidepressants and psychostimulants medications. Whilst young males (0-17 years) were slightly more likely than females to have accessed a Nervous system prescription, for all other age groups females were more likely than males. The largest difference between males and females was at ages 65-74 years (41.9% compared with 54.3% respectively). Generally, use of Nervous system medications increased with age and people aged 75 years and over had the highest rate of any age group, with six in ten people (61.7%) having accessed a Nervous system prescription via the PBS.

Cardiovascular system medications were the third most commonly accessed subsidised prescription in the linked dataset and are used in treating cardiovascular disease, such as heart, stroke and vascular disease. They are also used to prevent risk factors such as high blood pressure and high cholesterol. Rates of use generally increased with age for both males and females with a similar proportion of males and females in each age group. There was a slight difference at ages 55-64 years with 48.4% of males compared with 40.4% of females. Generally, use of Cardiovascular system medications increased with age and people aged 75 years and over had the highest rate of any age group at 85.1%.

Long-term health conditions are typically managed by prescribed medications. However, there is no detailed information regarding what conditions prescription medications are being prescribed for in the PBS and limited information from the NHS. To better understand the relationship between long-term health conditions and medication use, the integrated data can be used to cross-classify and highlight medication prescribing patterns in the PBS subsidised prescriptions to better understand comorbidity and polypharmacy.

This section looks at those people who self-reported a long-term health condition in the 2014-15 NHS and the types of PBS subsidised prescriptions they accessed in the 12 months prior to 2014-15 NHS interview. Long-term health conditions self-reported by respondents in the 2014-15 NHS are presented using a classification originally developed for the 2001 NHS by the Family Medicine Research Centre, University of Sydney, in conjunction with the ABS. The classification is based on the 10th revision of the International Classification of Diseases (ICD).

Of those people who self-reported a long-term health condition in the 2014-15 NHS, the proportion who accessed at least one PBS subsidised prescription were as follows:

• Hypertension and Diabetes mellitus – both at 97.3%
• Osteoporosis – 96.0%
• Heart, stroke and vascular disease – 95.6%
• Chronic obstructive pulmonary disease (COPD) – 92.7%
• Cancer (malignant neoplasms) – 91.5%
• Arthritis – 91.2%
• Kidney disease – 91.0%
• Asthma – 87.5%
• Mental and behavioural conditions – 84.6%
• Back problems (dorsopathies) – 80.0%
• Hayfever and allergic rhinitis – 72.2%

For further information on prevalence rates of self-reported long-term health conditions in the 2014-15 NHS, see 4364.0.55.001 - National Health Survey: First Results, 2014-15.

Of those who self-reported a long-term health condition, the following PBS subsidised prescriptions were accessed:

• Of those who self-reported having Hypertension, 93.5% had at least one PBS subsidised prescription for Cardiovascular system medications.
• More than four in five (85.2%) of those who self-reported having diabetes had at least one Alimentary tract and metabolism script, which comprises medications targeted for diabetes. This was closely followed by Cardiovascular system (83.0%) which could be explained by people with diabetes often taking blood pressure lowering medications in combination. People who have diabetes are at risk of heart disease. Heart attacks and strokes are up to four times more likely in people with diabetes[10].
• Seven in ten (70.3%) who self-reported having COPD had a PBS subsidised prescription for Antiinfectives for systemic use. This medication group includes antibiotics which are commonly used for the management of COPD.
• Four in five people (83.2%) who self-reported having Heart, stroke and vascular disease had a Cardiovascular system script. Around half of these people (50.4%) with this condition also had a PBS subsidised prescription for Blood and blood forming organs medication.
• Musculo-skeletal medications were most commonly accessed by people who self-reported having Osteoporosis at 51.4%.
• More than half of the people who self-reported having COPD (53.9%) and Asthma (53.0%) had a PBS subsidised prescription filled for a Respiratory system medication.
   

The aim of this exploratory analysis was to showcase the use of PBS subsidised prescriptions with NHS data and to assess the feasibility of using PBS subsidised prescriptions to replace the medications questionnaire module in future cycles of the NHS. Based on the analysis, the administrative data provides similar or higher quality information for most ATC Classification System medications groups compared to survey data.

After comparing two time windows, the analysis illustrates the PBS subsidised prescriptions should align as close to the NHS reference period as possible in order to achieve conceptually comparable results. However, for analysis purposes utilising PBS subsidised prescriptions over a longer period would allow for a larger breadth of research to be undertaken. An advantage of the PBS subsidised prescriptions data is the availability of a range of time periods which can be chosen depending on the research question, whereas the NHS data is constrained to a two week window for the purposes of improving respondent recall and to reduce cognitive load.

In the NHS, respondents would still be asked about medications used for specific long-term health conditions of cardiovascular disease, diabetes and high sugar levels, and asthma medication use. This is due to the high priority data need to ascertain the treatment and management of these long-term health conditions to help improve outcomes.

As illustrated in the analysis, over-the-counter medications are a data gap in the PBS subsidised prescriptions. It would be worth investigating how to expand or complement the medications data represented in the MADIP asset to include over-the-counter medications, private prescriptions, dietary supplements and other data gaps. Investigations into questions related to over-the-counter medications, such as aspirin and Ventolin have already begun for use in future NHS cycles.

By using PBS subsidised prescriptions, there is an opportunity to expand the information available to be published such as: the number of prescriptions dispensed; the frequency of scripts; amount of medicine supplied; time between prescriptions; and costs associated, for example, benefit amount or patient contribution amount.

Future linkage between NHS and MADIP could also support additional analysis into relationship outcomes such as; mortality, barriers to health care, hospitalisations and visits to emergency departments with access to prescription medications. Such analysis would be valuable for better understanding and improving health outcomes in Australia.

This release previously used catalogue number 4364.0.55.015