Expectations and attitudes in primary care towards home-based testing for diagnosing asthma: a mixed-methods study

We thank the authors for their interest in our published work exploring primary care healthcare professionals' perspectives on home-based testing for asthma.¹

We agree with the authors' view that the challenges of home diagnostic testing in children mean that evaluations of test strategies are likely to place different emphasis on outcomes and priorities than those in adults. The authors also rightly point out that patient perspectives and the diagnostic accuracy of these tools in children should be evaluated separately from adults, as reference ranges are likely to differ.

To take this further, there are also important differences within paediatric age groups themselves. For example, preschool-aged children may face different challenges regarding test acceptability compared with school-aged children, while adolescents may encounter a different set of user barriers. From a healthcare professional perspective, although many of the barriers and enablers may be similar across age groups, the emphasis placed on factors such as training needs and support requirements may differ substantially by age, but may also be influenced by non-age-related factors such as limited digital literacy and dexterity, language barriers, or other additional needs. This is therefore not simply a question of children versus adults. As we have previously demonstrated in adults,² different individuals may face different barriers and therefore require different levels and types of support. We therefore agree that implementation must be carefully evaluated to maximise inclusivity for all, and that early stakeholder engagement is vitally important in this regard.

With advances in technology, however, we are in a unique era where many of these barriers may be more readily addressed through digital tools, at least for some patients. Remote video training and coaching of home spirometry can be delivered and have previously been shown to be feasible and effective in paediatric populations.³ Furthermore, digital technologies may help improve technique, or at least allow recordings or quality checks that enable suboptimal technique to be identified and appropriately accounted for. Results can also be logged automatically, representing a substantial improvement over traditional home peak flow meters and paper-based diaries. Because longitudinal home testing captures variability over time rather than a single static measurement, if variability metrics prove clinically useful, for example to demonstrate variable airflow obstruction using FEV1, a degree of technical imperfection may be acceptable, provided that technique remains consistent within an individual, although this requires further evaluation.

The authors were also right to highlight that FeNO is substantially influenced by growth and development during childhood, as we have also previously reported.⁴ Digital technology may help address some of these challenges, for example by automatically providing age-adjusted predicted values for interpretation, such as is done for spirometry. However, the first challenge is determining which reference equations should be used, as the Global Lung Function Initiative was unable to generate a universal equation because of substantial heterogeneity between datasets.⁵ Furthermore, home FeNO parameters, whether based on average values or measures of variability across multiple time points, should not necessarily be regarded in the same way as a one-off FeNO measurement when developing prediction equations, as FeNO demonstrates substantial variability.^6–8 These home-based parameters must therefore first be adequately evaluated and validated before reference equations specific to home FeNO monitoring can be developed.

It is important to highlight that home-based testing tools are unlikely to replace existing diagnostic approaches, but rather to complement them and hopefully help some patients. Given the heterogeneity of asthma and patient populations, home testing is unlikely to be suitable for everyone. For example, if home spirometry and FeNO are shown to capture asthma more effectively than one-off testing, whether in children, adults, or both, they could be incorporated into existing diagnostic pathways and potentially reduce the need for investigations such as bronchial challenge testing. This may be particularly valuable in children, where access to the test is even more limited than for adults, even in specialist care settings, and waiting times is prolonged.⁹ Furthermore, access to respiratory diagnostic testing disproportionately affects individuals from more deprived areas where respiratory illnesses are more prevalent, potentially widening existing health inequalities.¹⁰ Novel tools that provide alternative routes to specialist diagnostic testing may therefore help to improve access and reduce such inequalities if implemented correctly. Digital transformation is likely to play an increasing role in NHS service delivery,¹¹ although digital exclusion remains an important consideration and alternative diagnostic pathways must remain available.

In summary, we agree with the authors that children are not simply smaller adults and thank them for highlighting this important consideration. Indeed, the challenge may be even more nuanced, with important differences existing across paediatric age groups themselves, as well as other important non-age related factors. These considerations warrant specific attention in future studies evaluating diagnostic accuracy and patient acceptability. Nevertheless, the promise of digital home-based testing in asthma is clear, and careful evaluation is needed to generate the evidence required to improve the diagnosis of this highly prevalent condition.

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