UK Researchers Push Back on Study Showing Cystic Fibrosis Outcomes Better in US Versus UK

A new editorial entitled “Comparing cystic fibrosis outcomes across the pond” was recently published online in the journal Thorax. In the editorial, David C Taylor-Robinson from the Department of Public Health and Policy, at the University of Liverpool in the United Kingdom along with colleagues discuss the results a study published in the same issue of Thorax, conducted by Goss and colleagues that found that children and young people with Cystic Fibrosis in the United States have better lung function than in young people from the United Kingdom.

As part of the original study, Goss and colleagues collected registry data from the UK and the US and compared the outcomes and use of treatments between the two countries, noting that the US reports better clinical outcomes and intervention treatments in terms of lung function in children. However, while Dr. Taylor-Robinson and colleagues acknowledge the importance of cross-country comparison studies in Cystic Fibrosis, the UK researchers regard these results with skepticism, stating that there might be some ascertainment bias in the results, especially in the variables of mean % predicted FEV₁.

The UK researchers state that variables such as measurements of lung function in CF, as well as variances in ethnic and genetic makeup may be different between the two countries, thus making it difficult to compare the two populations.

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Moreover, David C Taylor-Robinson and colleagues indicate that the way that data is collected between the two countries is fairly different. For example, in the UK, the registry is estimated to capture almost all of the CF population, and any patients attending the National Health Service clinics will have data routinely collected into the database. Conversely, the US registry collects data on patients seen in US accredited CF centers, which may offer lower coverage of the American CF patient population. Because of the high level of population coverage in the UK, the UK registry may represent more disadvantaged groups, leading the UK studies to reveal worse clinical outcomes when compared to the US studies.

The UK researchers suggest that alternatives to explaining the lung function gap could relate to organization of care, particularly frequency of access to centre-based care.

The researchers also pointed out that children attending large CF centers more frequently in the early years in the UK achieve better outcomes, while results from the US indicate that the highest lung function is associated with more clinic visits, more respiratory tract cultures and frequent antibiotic treatment of patients, particularly those considered to have mild lung disease. Since ideal treatment of pulmonary exacerbations is a key factor in terms of achieving better pulmonary outcomes, this may further explain the differences found in the study, however UK authors note that because of the different registry parameters in both countries, the results are not comparable.

David C Taylor-Robinson and colleagues indicate that longitudinal trials are necessary in young people before conclusions can be drawn between treatments and long-term outcomes using registry data. The authors concluded by stating the importance of cross-country comparisons, since then can highlight important differences in outcomes and care for people with CF between countries.