Country selection in the COPD Index was informed by the importance of broad geographic representation, as well as the inclusion of countries able to represent the extent of the global COPD burden. A key inclusion criterion was the existence of a de jure or de facto universal health coverage scheme or statutory requirement for health insurance coverage for the national population. Notably, the United States was excluded for this reason.
Data availability also determined the inclusion of countries in order to ensure as complete a dataset as possible. Specifically, we selected countries that regularly publicly report data that has been validated by recognised international or supranational institutions. The number of countries included ensured that the size of the dataset was neither too small (which would not be sufficient to identify trends) nor too large (which would present challenges such as heterogenous availability of data and increased complexity of analysis/results).

A Steering Committee was established to validate the data and to lead decision-making regarding the design and content of the COPD Index. The committee includes eight global COPD and health policy experts. The members were selected in order to balance clinical knowledge in COPD, patient organisation leadership, and expertise in health policy development and implementation.

CIFS conducted a preliminary review of the literature regarding COPD to:

■ Develop a robust understanding of the condition, including its varying definitions,
reports on disease incidence and prevalence, risk factors, comorbidities, and overall
impact on individuals, societies, and health systems
■ Identify usual clinical practice including diagnosis, standard of care, and stratification
■ Determine access and reimbursement of COPD management and care
■ Identify health policies addressing COPD and associated risk factors

These insights then informed the identification of potentially relevant and viable indicators to be included in the Index, as well as potential sources of data.

Insights from the literature review supported the identification of indicators, i.e., qualitative and quantitative variables both directly and indirectly linked to patient health outcomes or impacting the ability of country health systems to manage and prevent COPD among country populations. We identified over 70 potential indicators that were broadly grouped into five categories:

■ Policy Context
■ Access and Care Coverage
■ Health System Characteristics
■ Disease Burden
■ Environmental Factors

The indicator categories were structured to facilitate a multifaceted analysis of health system performance concerning COPD. As a result, COPD was examined not only as a clinical issue, but also as a disease impacted by public policy, health system design, comorbidities, and environmental factors.

The draft indicators were prioritised and validated by the COPD Index Steering Committee through two rounds of review. Review of the indicator list first took place in a group workshop with the Steering Committee and then through individual written feedback.
The process resulted in a final list of 45 indicators across the five indicator categories (see Appendix II for the list of indicators and category assignments). The exclusion and addition of indicators was based on an assessment of conceptual goodness of fit, data availability, and convertibility, i.e., whether the raw indicator data could be feasibly and meaningfully quantified in the index data model.

Data collection commenced upon receiving validation of the prioritised list of indicators.
Data collection took place between February and July 2024, and was conducted in several ways:

Desktop research
The research team identified and collected relevant data points from credible, publicly available sources such as the OECD, WHO, World Bank, and Eurostat databases as well as from peer-reviewed articles and reports and other official documents authored or approved by relevant public authorities in each country included in the index.

Expert questionnaire
To supplement desktop research, the research team designed a two-round questionnaire for the collection of a wide range of COPD specific information. The first round of the questionnaire was a mixed e-Delphi study, i.e., several sections exclusively contained questions and statements seeking the expert opinion of respondents to identity whether a degree of consensus existed among the group (e.g., “The burden of COPD in my country will place significantly more strain on my country’s health care system by 2035.”), whereas other questions sought to collect information of a purely factual nature (e.g., “Does your country have an action plan for COPD?”). The second round of the questionnaire focused solely on consensus-seeking questions.
The questionnaire forms were validated by the COPD Index Steering Committee before being submitted to respondents (see Appendix IV for the questionnaire form).
The questionnaire was distributed online to over 300 potential respondents. The response period ran from April to August 2024.
Respondents were selected based on the following occupational/professional criteria with the intention of maximising the diversity of responses:

■ Civil servant with a role in a national public health institution or equivalent body
■ Medical respiratory specialist, preferably with an affiliation or assignment with a
national health institution or research institution
■ Primary care physician with a background in respiratory health
■ COPD patient advocacy group representative
■ COPD patient
■ Carer for COPD patients

96 responses covering 24 COPD Index countries were received. Responses to the factseeking questions in the first round of the e-Delphi were used to support the calculation of selected indicator scores where data from existing sources were assessed as having a low level of
reliability or were unavailable. Qualitative data collected in the first round of the e-Delphi, such as examples of challenges to and opportunities for COPD diagnosis, prevention, and management identified by respondents were not used to calculate indicator or country scores. However, they were used to provide additional context for individual country profiles (See Appendix I)

Raw data from desktop research and the questionnaire were matched with each of the validated indicators and then organised into the approved indicator categories. To maximise conceptual fit with some indicators, several data points were also combined to create compound variables. Qualitative data points were quantified through the application of scorecards designed by the research team. The scorecards associated different point values with a set of standardised qualitative characteristics, for example, whether a country has a set of national guidelines for COPD care and, if so, what the general level of adherence to the guidelines is among health care professionals. Indicators based on qualitative data have scorecards with different maximum values; these values depend on the characteristics examined in the COPD 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 qualitative data, all data points in the Index were normalised on a 0 to 10 scale using the min-max normalisation method. This approach allows for uniform analysis of many different types of data originally recorded on different scales.
On the normalised scale, a score of 10 always indicates a high level of fulfilment of the Index model’s criteria for a given indicator, while a score of 0 always indicates a low level of fulfilment. Minimum values were set at 0 (the theoretical minimum value of the raw dataset for each indicator), while maximum values were set at either the theoretical maximum (for example, 100 for raw data recorded as percentages), three standard deviations above the mean of the raw dataset for each quantitative indicator (in the case of data recorded as absolute values), or the maximum scorecard value for each qualitative indicator. In the case of extreme outliers in the dataset, the maximum value was set at the value of the greatest outlier.
Following normalisation, country scores for each indicator category were averaged and then multiplied by 10 to produce a score out of 100 points. The purpose of the conversion to a 100-point scale on the category level is to reflect smaller differences in country scores that would otherwise be expressed as decimals.

Weighting

To produce an overall Index score, both individual indicators and indicator categories were weighted. The budget allocation approach was applied to identify indicator and category weights: Each member of the COPD Index Steering Committee was tasked with individually assigning weights to the components. The results of the individual inputs were shared with the Steering Committee during a group workshop in June 2024. CIFS then provided a proposal for the component weighting based on the group discussion, which was approved by the Steering Committee in June 2024. The following weights were applied to each indicator category when calculating the overall Index score for each country:



Individual indicator weights are listed in the Indicator List in Appendix II.

The weighting approach emphasises elements of the Index that can be directly addressed by decisionmakers and key stakeholder groups. The Policy Context, Access and Care Coverage, Health System Characteristics, and Environmental Factors categories are therefore more heavily weighted in the Index because they include indicators that directly reflect factors which a country’s decisionmakers and stakeholders have control over. The Disease Burden category is less heavily weighted because it is linked to longerterm health outcomes and indirect factors impacting COPD management and outcomes.
The assigned weights aim to reflect the Index’s primary ambition to motivate concerted action among health care stakeholders and the adoption of best practices that stand to improve health outcomes, health system performance, and ultimately address factors affecting prevention, prevalence and severity of COPD among populations. However, all indicator categories are fundamental to supporting a multifaceted analysis of countries’ management and prevention of COPD

The results yielded by the Index data model were compared using descriptive statistics on both the aggregate and individual country levels. Correlation between several indicators was also investigated to determine whether significant relationships exist between any variables. Additional relationships between country indicator data and data not used to calculate country scores were also explored to further contextualise country results and identify future potential areas of inquiry regarding COPD prevention, diagnosis, and management.

Important note on scoring in the COPD Index data model
The COPD Index is constructed as an ideal and abstract model for COPD care and management. This means that 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 COPD.
Rather, the overall Index score and category scores should be understood as indications of how well country health system COPD approaches and performance fit the ideal model proposed by the COPD Index. Scores also highlight best practices that country health systems could learn from and adapt to their local needs as well as demonstrate potential areas for improvement.

The COPD Index is a powerful tool for identifying best practices in COPD care and analysing country health system performance against an ideal model for COPD care.
However, the index is still bounded by several important limitations that must be kept in mind when exploring its insights and the data on which they are built.

Country selection
Country selection is in part informed by data availability, leading to the exclusion of some countries, primarily in Africa, that reduces the global representativeness of the Index results. Furthermore, the key inclusion criterion, i.e., the existence of a de jure or de facto universal health coverage scheme or statutory requirement for health insurance coverage for the national population in the countries led to the notable exclusion of the United States.

Data availability and accuracy
There are significant limitations on the availability, accessibility, and accuracy of COPD related data. In some cases, differing definitions of COPD and COPD stages may be used, rendering exact comparison between countries difficult and, in some cases, impossible.
Data fragmentation and a lack of harmonised rules for data reporting and access across the Index countries creates barriers to collecting COPD-specific information. In addition, several sources of information may be used to build the dataset for a single indicator. It is also crucial to note that country-reported data may, in some cases, reflect a tendency to underreport or misreport some data or outcomes.

Time lag and time series
The inclusion of various kinds of data in the Index has necessitated the use of data that has been collected at different time points. The Index makes use of the latest data wherever possible, but there is still variance in the time series within and across indicators. Differences in time series in the dataset are always indicated in the COPD Index sources.

Missing data and imputation
Data points for some countries are not reported or 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 indicated in the Index.

Data reliability and inferred data
The reliability of data collected for a small number of indicators is contested. These data points are linked to sources that provide a direct indication of how the country indicator should be scored, but other sources and contextual information indicate that the value may not be accurate. These data points are indicated in the COPD Index data model as having lower reliability. For a small number of selected qualitative indicators, scores have been inferred based on an assessment of identified sources that do not provide direct indications of how a country indicator should be scored but do provide sufficient contextual information. Inferred data points are also explicitly identified in the COPD Index data model.

Proxy indicators and conceptual accuracy
Several proxy indicators have been developed, in part based on input from the Steering Committee, to approximate data that are not currently directly reported. These proxy indicators may, in some cases, be based on a composite of several sources of data. Proxy indicators and their method of calculation are always listed in the Index.

Intra-country differences and generalisation
The whole-country approach of the COPD Index may risk generalising intra-country differences such as urban/rural divides and differences in regional approaches to care, especially in geographically large countries, federalised countries, and countries with highly devolved health care systems.

Policy implementation and lived experience
Nuances related to how countries’ policies and conditions for care access function may not be fully expressed, as the Index framework takes a country-wide approach that assesses reported system characteristics rather than the day-to-day operational environment. It is also crucial to note that the lived experiences of patients and health care providers are not directly assessed, as these are reliant on often highly variable and subjective reports that do not lend themselves to reliable cross-country comparisons in the context of a quantitative index data model.