Insights
Data from the Severe Asthma Index revealed the following key insights about severe asthma care across the 29 OECD countries evaluated.
Severe Asthma Index
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Severe Asthma Index Table
Policy Context
Guidelines, strategies, and policies related to the management of severe asthma and health outcomes.
Access and Care Coverage
Regulations and practices concerning public payor coverage for and availability of diagnostic and treatment services for severe asthma.
Health System Characteristics
Indicators related to clinical management and economic impact of severe asthma and recording of patient health data.
Disease Burden
Information about the health impact of severe asthma and severe asthma comorbidities.
Environmental Factors
Factors impacting prevention, management, and exacerbations of severe asthma.
Data scoring and normalisation
Raw data collected from desktop research and the questionnaire were matched with each of the validated indicators and then organised into the approved indicator categories. Qualitative data points were quantified through the application of scorecards designed by the research team. The scorecards associate different point values to a set of standardised qualitative characteristics, for example, whether a country has a set of national guidelines for severe asthma care. Indicators based on qualitative data have scorecards with different maximum values; these values depend on the characteristics being examined in the Severe Asthma Index.
Several qualitative indicators are dichotomised in the Index, i.e., 1 point may be assigned if a given condition is fulfilled, while a score of 0 is assigned if the condition is not fulfilled.
Following the scoring of the quantitative data, all data points in the Index were normalised on a 0 to 10 scale using a min-max normalisation method. This approach allows for uniform analysis of many different types of data that have originally been recorded on different scales. On the normalised scale, a score of 10 indicates a high level of fulfilment of the Index model’s criteria for a given indicator, while a score of 0 indicates a low level of fulfilment.
Following normalisation, country scores for each indicator category were averaged and then multiplied by 10 to give a score out of 100 points. The conversion to a 100-point scale on the category level is to reflect smaller differences in country performance that would otherwise be expressed as decimals.
To produce an overall Index score, country performance in each of the indicator categories was averaged and weighted. The following weights were applied to each indicator category when calculating the overall Index score for each country:
Category/Description
Weight
Policy Context
30%
Access and Care Coverage
25%
Health System Characteristics
20%
Disease Burden
15%
Environmental Factors
10%
The weighting approach emphasises elements of the Index that can be directly addressed by decisionmakers and key stakeholders/stakeholder groups. The Policy Context and Access and Care Coverage categories are therefore more heavily weighted in the Index because they include indicators that directly reflect or are expressions of conditions over which country decisionmakers and stakeholders have control. The remaining categories in the Index are less heavily weighted because they are either linked to longer-term health outcomes and health system performance and/or indirect factors impacting severe asthma management and outcomes. The assigned weights aim to reflect the Index’s primary ambition to motivate policy actions and adoption of best practices that should improve health outcomes, health system performance, and ultimately address factors affecting the prevalence and severity of asthma among populations.
Important note on scoring in the Severe Asthma Index data model
The Severe Asthma Index is constructed as an ideal and abstract model for severe asthma care and management. In this way, no country is expected to receive a perfect score in the Index. Crucially, the scoring system should not be understood as an expression of how objectively “good” or “bad” a country health system is at managing and preventing severe asthma. Rather, the overall Index score and category scores should be understood as indications of how well the country health system approaches and performance concerning severe asthma fit the ideal model that the Severe Asthma Index proposes.
Limitations
The Severe Asthma Index is a powerful tool for identifying best practices in severe asthma care and analysing a country's health system performance against an ideal model for severe asthma care, but it is still bounded by several important limitations that must be kept in mind when exploring the Index insights and the data on which they are built:
Data availability and accuracy
There are significant limitations on the availability and accuracy of severe asthma-related data. In many cases, there is a lack of disaggregation in health data indicating asthma severity. Therefore, several sources of information may be used to build the dataset for a single indicator.
Time lag and time series
Inclusion of many different kinds of data in the Index has necessitated the use of data that has been collected at different periods in time. The Index makes use of the latest data wherever possible, but there is still variance in the time series within and across indicator data. Differences in time series in the dataset are always indicated in the Index.
Missing data and imputation
Data points for some countries are not reported or are non-existent. In such instances, data has been imputed by calculating the average value for the given indicator using the reporting countries’ data. Imputed values are always indicated in the Index.
Proxy indicators and conceptual accuracy
Several proxy indicators have been developed to approximate data that are not currently directly reported. These proxy indicators may in some cases be based on a composite of several variables. Proxy indicators and their method of calculation are always listed in the Index.
Generalisation
The whole-country approach of the Severe Asthma Index may risk generalising intra-country differences such as urban/rural divides and differences in regional approaches to care, especially in federalised countries and countries with highly devolved healthcare systems.
COVID-19
Several data points may be influenced by the impact of the COVID-19 pandemic on health system capacity, performance, planning, and access.
Index Score Weighting
The weighting approach emphasises elements of the Index that can be directly addressed by decision makers and stakeholders.
Overall Index Score
The weighting approach emphasises elements of the Index that can be directly addressed by decision makers and stakeholders.
The Index Goal
To give change makers the information they need to take action toward improving the standard of care in severe asthma.