Quality-Adjusted Life Years (QALY) in Cost-Effectiveness Analysis
In pharmaceutical research and healthcare economics, the concept of Quality-Adjusted Life Years (QALY) is an important tool for evaluating the cost-effectiveness of medical interventions. QALY establishes a single metric to measure health benefit. This means that QALY can be used in the cost-effectiveness analysis (CEA) of different healthcare interventions or products. For example, many health technology assessment (HTA) bodies such as the National Institute of Health and Clinical Excellence (NICE) in England and Wales and Canada’s Drug Agency (CDA) use QALY in their CEA of healthcare interventions or products to support decisions regarding the allocation of scarce financial resources.
How are QALYs calculated?
Calculating a QALY requires two components:
- Duration: Number of years lived in a given health state
- Utility Value: Quality of Life (QoL) is characterized by a utility value ranging from 0 (death) to 1 (perfect health)
QoL can be measured using multi-attribute utility (MAU) instruments, e.g. EuroQol five-dimension (EQ-5D), Short-Form 6-Dimension (SF-6D), Health Utilities Index (HUI) etc. MAUs are composed of two elements. The first element contains questions to measure health, and the second is a preference-based formula which is used to derive utility values from the instrument’s score. Preferences are obtained to establish how to weight utility values in different ways. For example: standard gamble, time-trade off, person-trade off, discrete choice experiment.
Once a QALY has been obtained, it is incorporated into an incremental cost effectiveness ratio (ICER). The ICER is calculated by taking the ratio between the incremental cost and the incremental QALY, which gives you the cost per additional QALY gained.
What if a MAU instrument has not or cannot be used?
In some cases, utility values are not established during a study, e.g. a MAU instrument was not administered. In other cases, it might not be appropriate to administer a MAU instrument in a specific population and/or therapeutic indication. For example, in some rare diseases it is unclear whether the responsiveness of MAU instruments like the EQ-5D is adequate.
In cases where an MAU instrument has not or cannot be used, mapping is used to provide comparable utility values from a non-MAU instrument based on an MAU instrument such as the EQ-5D. Mapping refers to the process of estimating the relationship from a clinical outcome assessment (COA) to a utility value that can be derived from MAU instruments such as the EQ-5D. Essentially, it is a way of ‘bridging the evidence gap’ between the available study data and the need to establish a utility value for QALY analysis. This enables the results from a non-MAU instrument to be incorporated into cost-effectiveness analysis (CEA).
A unique tool to identify COAs mapped to a utility instrument
The Health Economics Research Centre’s (HERC) mapping database includes studies that conducted statistical mapping to predict EQ-5D utilities or responses from any source instrument, and reported the estimated algorithms in sufficient detail to allow other researchers to use them to predict EQ-5D in other studies*.
All COAs and MAUs with an identifiable development paper that are described in the University of Oxford’s HERC mapping database are described in PROQOLID™.
PROQOLID™ is a unique and comprehensive online database providing information about the development, validity, content, conditions of use, translations, and copyright of over 7,000 COAs.
In addition, any instrument (COA or MAU) from which a utility value can be established that is featured in a guideline described in PROINSIGHT™ is linked in the ‘Related data to consider’ section of the PROQOLID™ page. PROINSIGHT™ is a database from Mapi Research Trust that summarizes and centralizes regulatory recommendations COAs.
To discover MAUs as well as COAs that have been mapped to a MAU, please visit PROQOLID™.
Debates on QALY
There has been a pushback in the USA against the use of QALYs in CEA. This has led to the use of QALYs being prohibited in Medicare coverage/reimbursement decision-making by the Affordable Care Act. The main arguments against QALY have centered on the notion that it is discriminatory against certain populations, such as the elderly or terminally ill, since greater value is placed on years lived.
However, a recent collection of papers published in Value in Health refute these claims and outline why, whilst imperfect, the QALY remains an important part of CEA for health interventions and products worldwide. Further, more recently proposed alternatives such as the health years in total (HYT) or the Equal Value of Life Years Gained (evLYG) still present inconsistencies and are not yet viable alternatives to the QALY.
In sum, QALYs play a pivotal role in shaping healthcare decisions and resource allocation across the globe. While debates continue about their limitations and potential alternatives, QALYs remain a cornerstone of health economic evaluations. The development of mapping techniques and databases like PROQOLID™ demonstrates the ongoing efforts to refine and expand the utility of this metric and ultimately, benefit patients.
*Note: mapping algorithms to other preference-based measures that are reported in the same publication as algorithms mapping to EQ-5D are also presented.