Post-market Review of Chronic Obstructive Pulmonary Disease Medicines ToR 5 Final Report August 2017

5.2 Introduction

In October 2013, DUSC reviewed the PBS utilisation of indacaterol for COPD. The review identified co-administration of multiple LABA products in some patients, which is not supported by PBS prescribing restrictions or clinical practice guidelines. This was considered a significant QUM issue. Due to limitations in the information available, DUSC could not determine whether this QUM issue was due to inappropriate prescribing of multiple products by the clinician or inadvertent improper poly-pharmacy due to a lack of understanding on behalf of the clinician or patient.

The following utilisation review was conducted to identify the extent of co-prescribing and medication use that is inconsistent with clinical guidelines and/or PBS restrictions using PBS/RPBS claims data. The MedicineInsight Post-Market Surveillance Report 11 was developed with the purpose of informing the post-market review and medicines policy for COPD. Results from the MedicineInsight Post-Market Surveillance Report 11 are summarised in this section, with the full report at Appendix T.

5.3 PBS/RPBS claims data sources and limitations

5.3.1 Department of Human Services (DHS) PBS claiming system

A preliminary analysis of PBS/RPBS services and benefits was conducted using the DHS PBS claiming system. Claims for reimbursement for the supply of PBS or RPBS subsidised medicines are submitted by pharmacies to the DHS PBS claiming system (PBS Online) for processing. PBS/RPBS services and benefits claims data was extracted from the DHS PBS statistics website on 11 April 2017 for preliminary analysis. The prescription and benefits data is based on the date the prescription was processed, that is, the date on which PBS Online finalises the payment for a prescription. However, some of these scripts could be adjusted later if errors were found by suppling pharmacies or DHS during a final reconciliation. The analysis conducted using the DHS claims data set is therefore subject to monthly variations resulting from bulk processing of prescriptions. The DHS PBS claims data includes the whole market, including all age groups, and asthma and mixed airways disease patients.

5.3.2 Department of Health (DoH) PBS claims database

A data file of individual record claims data was supplied from the Department of Health (DoH) PBS claims database. PBS and RPBS patient records were included in the dataset. The data set contained unique identifiers that enabled patient de-identification. PBS and RPBS data for ATC ‘H02’ and ’R03’ prescriptions were included in the analysis. The data analysis was conducted for prescriptions supplied between the periods of 1 November 2006 to 31 October 2016. Under co-payment prescriptions were included in the analysis from April 2012. As COPD is very uncommon among people aged less than 35 years, the dataset was restricted to patients aged 35 years and older (acknowledging that some patients in the dataset will have asthma or ACOS) as of 31 October 2016. The data was extracted on 31 January 2017. The supplied data file comprised approximately 113 million prescribing records (see data specification in Appendix N).

Caution should be taken when interpreting analyses based on PBS/RPBS prescription claims data as there are important limitations with the data set, including:

Population

Medications provided during hospitalisation, or given on discharge from hospital, may not be captured in PBS prescriptions data.

Medications that are obtained through remote Aboriginal Health Service organisations are not captured.

Data availability

The recent PBS listing dates for some COPD medicines (particularly the FDCs listed in late 2015) means that it may be premature to try to accurately determine the nature and extent of their integration into treatment pathways for COPD patients.

Diagnosis and clinical information

The data set does not include information relating to patient diagnosis.

As bronchodilators and ICS are used for the treatment of both COPD and asthma, there is a risk that patients with asthma may be misclassified as COPD and vice versa. For PBS/RPBS items that are not restricted solely to the treatment of COPD (e.g. the ICS/LABAs, which are also listed for asthma), it is not possible to directly determine the underlying condition associated with the prescriptions dispensed. In this case, inferences need to be made, and the approach typically used by DUSC and the Australian Institute for Health and Welfare (AIHW) is to restrict the analyses to specific age groups. For instance, COPD is very uncommon among people aged less than 35 years and therefore it may be reasonable to assume that respiratory medications prescribed in this age group will not be for COPD. On the other hand, medications dispensed to people aged 35 years and over may include those prescribed for either COPD or asthma.

Patients with ACOS further complicate data interpretation as these patients are treated using a different algorithm and may be eligible for both COPD and asthma treatments. While there is some debate in the scientific community regarding the proportion of patients with ACOS, the estimate typically quoted in Australia is 15% (November 2010 PSD for indacaterol).

The data set does not contain clinical information about the reason for the prescription or the nature or severity of the condition for which the medication was prescribed. As such, it is not possible to determine whether PBS medicines are being used in the intended population according to the PBS restriction (e.g. the requirement for COPD patients to have a FEV₁ less than 50% of predicted normal prior to therapy in order to access an ICS/LABA on the PBS).

Switching and add on therapy

Assessing aspects of medication utilisation such as co-administration or switching between medicines is also not straightforward when based on prescription refill data alone.

The stepwise approach to COPD management, coupled with the selection of therapies available on the PBS, means that patients switch and add on therapies as needed to control symptoms, manage side effects, and simplify treatment regimens. This utilisation analysis has included assumptions relating a standard prescription coverage period to account for switch and add on therapy.

Compliance and adherence

PBS/RPBS data do not provide information on prescriptions written by a health care professional that are not filled by the patient, thereby making assessment of primary non-adherence and prescriber intent difficult.

The data does not indicate whether or how often a medication was actually used. Patients may not be completely adherent to their prescribed therapy.

Poor adherence with COPD treatments is frequently observed, despite it being a highly symptomatic disease. Compliance issues can confound analyses as the prescription coverage period may be appear longer, however it does not represent consistent medicine use.

Stockpiling

Stockpiling of medication is a phenomenon that can cause data anomalies and must be taken into account when analysing PBS claims data. Stockpiling can occur at any time of the year, but often occurs towards the end of the calendar year when a Safety Net card holder fills prescriptions more frequently than expected, so as to avoid a higher co-payment in the first few months of the next calendar year when they lose Safety Net eligibility.