Feasibility study for supporting medication adherence for adults with cystic fibrosis: mixed-methods process evaluation

Consolidated guidance for behavioral intervention pilot and feasibility studies

BACKGROUND

In the behavioral sciences, conducting pilot and/or feasibility studies (PFS) is a key step that provides essential information used to inform the design, conduct, and implementation of a larger-scale trial. There are more than 160 published guidelines, reporting checklists, frameworks, and recommendations related to PFS. All of these publications offer some form of guidance on PFS, but many focus on one or a few topics. This makes it difficult for researchers wanting to gain a broader understanding of all the relevant and important aspects of PFS and requires them to seek out multiple sources of information, which increases the risk of missing key considerations to incorporate into their PFS. The purpose of this study was to develop a consolidated set of considerations for the design, conduct, implementation, and reporting of PFS for interventions conducted in the behavioral sciences.

METHODS

To develop this consolidation, we undertook a review of the published guidance on PFS in combination with expert consensus (via a Delphi study) from the authors who wrote such guidance to inform the identified considerations. A total of 161 PFS-related guidelines, checklists, frameworks, and recommendations were identified via a review of recently published behavioral intervention PFS and backward/forward citation tracking of a well-known PFS literature (e.g., CONSORT Ext. for PFS). Authors of all 161 PFS publications were invited to complete a three-round Delphi survey, which was used to guide the creation of a consolidated list of considerations to guide the design, conduct, and reporting of PFS conducted by researchers in the behavioral sciences.

RESULTS

A total of 496 authors were invited to take part in the three-round Delphi survey (round 1, N = 46; round 2, N = 24; round 3, N = 22). A set of twenty considerations, broadly categorized into six themes (intervention design, study design, conduct of trial, implementation of intervention, statistical analysis, and reporting) were generated from a review of the 161 PFS-related publications as well as a synthesis of feedback from the three-round Delphi process. These 20 considerations are presented alongside a supporting narrative for each consideration as well as a crosswalk of all 161 publications aligned with each consideration for further reading.

CONCLUSION

We leveraged expert opinion from researchers who have published PFS-related guidelines, checklists, frameworks, and recommendations on a wide range of topics and distilled this knowledge into a valuable and universal resource for researchers conducting PFS. Researchers may use these considerations alongside the previously published literature to guide decisions about all aspects of PFS, with the hope of creating and disseminating interventions with broad public health impact.

A RCT to explore the effectiveness of supporting adherence to nebuliser medication in adults with cystic fibrosis: fidelity assessment of study interventions

BACKGROUND

A multi-component self-management intervention 'CFHealthHub' was developed to reduce pulmonary exacerbations in adults with Cystic Fibrosis (CF) by supporting adherence to nebuliser medication. It was evaluated in a randomized controlled trial (RCT) involving 19 CF centres, with 32 interventionists, 305 participants in the intervention group, and 303 participants in the standard care arm. Ensuring treatment fidelity of intervention delivery was crucial to ensure that the intervention produced the expected outcomes.

METHODS

Fidelity of the CFHealthHub intervention and standard care was assessed using different methods for each of the five fidelity domains defined by the Borrelli framework: study design, training, treatment delivery, receipt, and enactment. Study design ensured that the groups received the intended intervention or standard care. Interventionists underwent training and competency assessments to be deemed certified to deliver the intervention. Audio-recorded intervention sessions were assessed for fidelity drift. Receipt was assessed by identifying whether participants set Action and Coping Plans, while enactment was assessed using click analytics on the CFHealthHub digital platform.

RESULTS

Design: There was reasonable agreement (74%, 226/305) between the expected versus actual intervention dose received by participants in the CFHealthHub intervention group. The standard care group did not include focused adherence support for most centres and participants. Training: All interventionists were trained. Treatment delivery: The trial demonstrated good fidelity (overall fidelity by centre ranged from 79 to 97%), with only one centre falling below the mean threshold (> 80%) on fidelity drift assessments. Receipt: Among participants who completed the 12-month intervention, 77% (205/265) completed at least one action plan, and 60% (160/265) completed at least one coping plan. Enactment: 88% (268/305) of participants used web/app click analytics outside the intervention sessions. The mean (SD) number of web/app click analytics per participant was 31.2 (58.9). Additionally, 64% (195/305) of participants agreed to receive notifications via the mobile application, with an average of 53.6 (14.9) notifications per participant.

CONCLUSIONS

The study demonstrates high fidelity throughout the RCT, and the CFHealthHub intervention was delivered as intended. This provides confidence that the results of the RCT are a valid reflection of the effectiveness of the CFHealthHub intervention compared to standard care.

TRIAL REGISTRATION

ISRCTN registry: ISRCTN55504164 (date of registration: 12/10/2017).

Expert Perspectives on Pilot and Feasibility Studies: A Delphi Study and Consolidation of Considerations for Behavioral Interventions

Background

In the behavioral sciences, conducting pilot and/or feasibility studies (PFS) is a key step that provides essential information used to inform the design, conduct, and implementation of a larger-scale trial. There are more than 160 published guidelines, reporting checklists, frameworks, and recommendations related to PFS. All of these publications offer some form of guidance on PFS, but many focus on one or a few topics. This makes it difficult for researchers wanting to gain a broader understanding of all the relevant and important aspects of PFS and requires them to seek out multiple sources of information, which increases the risk of missing key considerations to incorporate into their PFS. The purpose of this study was to develop a consolidated set of considerations for the design, conduct, implementation, and reporting of PFS for interventions conducted in the behavioral sciences.

Methods

To develop this consolidation, we undertook a review of the published guidance on PFS in combination with expert consensus (via a Delphi study) from the authors who wrote such guidance to inform the identified considerations. A total of 161 PFS-related guidelines, checklists, frameworks, and recommendations were identified via a review of recently published behavioral intervention PFS and backward/forward citation tracking of well-know PFS literature (e.g., CONSORT Ext. for PFS). Authors of all 161 PFS publications were invited to complete a three-round Delphi survey, which was used to guide the creation of a consolidated list of considerations to guide the design, conduct, and reporting of PFS conducted by researchers in the behavioral sciences.

Results

A total of 496 authors were invited to take part in the Delphi survey, 50 (10.1%) of which completed all three rounds, representing 60 (37.3%) of the 161 identified PFS-related guidelines, checklists, frameworks, and recommendations. A set of twenty considerations, broadly categorized into six themes (Intervention Design, Study Design, Conduct of Trial, Implementation of Intervention, Statistical Analysis and Reporting) were generated from a review of the 161 PFS-related publications as well as a synthesis of feedback from the three-round Delphi process. These 20 considerations are presented alongside a supporting narrative for each consideration as well as a crosswalk of all 161 publications aligned with each consideration for further reading.

Conclusion

We leveraged expert opinion from researchers who have published PFS-related guidelines, checklists, frameworks, and recommendations on a wide range of topics and distilled this knowledge into a valuable and universal resource for researchers conducting PFS. Researchers may use these considerations alongside the previously published literature to guide decisions about all aspects of PFS, with the hope of creating and disseminating interventions with broad public health impact.

Nebuliser systems for drug delivery in cystic fibrosis

BACKGROUND

Nebuliser systems are used to deliver medications to the lungs, to control the symptoms and the progression of lung disease in people with cystic fibrosis (CF). There are many different nebulised-medications prescribed for people with CF and there are many different types of nebuliser systems. Some of these nebulised medications are licenced for, and can be taken via only one type of nebuliser system; some are licensed for, and can be taken via more than one type of nebuliser system. This is an update to a previous systematic review.

OBJECTIVES

To assess the time efficiency, effectiveness, safety, cost and impact of use (e.g. burden of care, adherence, quality of life (QoL)) of different nebuliser systems, when used with different inhaled medications for people with CF.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearching of relevant journals and abstract books containing conference proceedings. We searched the reference lists of each study for additional publications and approached the manufacturers of both nebuliser systems and nebulised medications for published and unpublished data. We also searched online trial registries. Date of the most recent search: 9 August 2023.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing nebuliser systems, including conventional nebulisers, vibrating mesh technology (VMT) systems, adaptive aerosol delivery (AAD) systems and ultrasonic nebuliser systems.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion. They also independently extracted data and assessed the risk of bias. A third review author assessed studies where agreement could not be reached. They assessed the certainty of the evidence using GRADE.

MAIN RESULTS

The search identified 216 studies with 33 of these (2270 participants) included in the review. These studies compared the delivery of tobramycin, colistin, dornase alfa, hypertonic saline and other solutions through the different nebuliser systems in children and adults with CF. This review demonstrates variability in the delivery of medication depending on the nebuliser system used. The certainty of the evidence ranged from low to very low. Some conventional nebuliser systems providing higher flows, higher respirable fractions, and smaller particles decrease treatment time, increase deposition (the amount of drug reaching the lung), and may be preferred by people with CF, as compared to other conventional nebuliser systems providing lower flows, lower respirable fractions and larger particles. Newer nebuliser systems using AAD, or VMT (or both) reduce treatment time compared to conventional systems. Deposition (as a percentage of priming dose) with AAD is greater than with conventional systems. VMT systems may give greater deposition than conventional systems when measuring sputum levels. The available data indicate that these newer systems are safe when used with an appropriate priming dose, which may be different to the priming dose used for conventional systems. There is an indication that adherence is maintained or improved and that individuals prefer AAD or VMT systems, but also that some nebuliser systems using VMT may be subject to increased system failures. There is limited, unclear evidence on the impact of different nebuliser systems on lung function and a lack of data on the impact of different nebuliser systems on our outcomes of quality of life (QoL), adverse effects, respiratory exacerbations and related implications, adherence, satisfaction, cost and device reliability.

AUTHORS' CONCLUSIONS

Newer technologies e.g. AAD and VMT have advantages over conventional systems in terms of treatment time, deposition as a percentage of priming dose, preference and adherence. Data are lacking for all varieties of medications which are used in CF care, including different inhaled antibiotics or hypertonic saline, with all delivery (nebuliser system) possibilities. Long-term RCTs are needed to evaluate different nebuliser systems to determine patient-focused outcomes (such as QoL and burden of care), safe and effective dosing levels of a wide variety of medications, clinical outcomes (such as hospitalisations and need for antibiotics), and an economic evaluation of their use. There are insufficient data to establish whether one nebuliser system is better than another overall. Clinicians should be aware of the variability in the performance of different nebuliser systems, compatibility with specific nebulised medication, and they must work with their patients to choose the best nebuliser system for each individual. This is likely to be an ongoing process as the needs and circumstances of each individual change over time.

Digital technology for early identification of exacerbations in people with cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is a life-limiting genetic condition affecting various organ systems including the gastrointestinal tract, endocrine system and especially the respiratory tract. Pulmonary exacerbations in CF result in increased symptoms, an acceleration in the rate of lung decline and an increased need for treatment. Early detection of infections or clinical worsening provides an opportunity for proactive treatment that may affect clinical outcomes.

OBJECTIVES

To evaluate whether digital technology can effectively predict pulmonary exacerbations to allow earlier intervention and improved health outcomes without increasing the burden of treatment in people with CF.

SEARCH METHODS

We used standard, extensive Cochrane search methods. We searched the Cochrane Cystic Fibrosis Trials Register and the reference lists of relevant articles and reviews on 13 October 2022. We searched Embase and the clinical trial registries on 3 January 2023.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) or quasi-RCTs in people with CF looking at whether digital technology can effectively predict pulmonary exacerbations to allow earlier intervention and improved health outcomes without increasing the burden of treatment.  DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. Our primary outcomes were 1. pulmonary exacerbations and 2. quality of life (QoL). Our secondary outcomes were 3. lung function, 4. hospitalisations, 5. intravenous (IV) antibiotics, 6. microbiology, 7. cost-effectiveness and 8.

ADVERSE EVENTS

We used GRADE to assess certainty of evidence.

MAIN RESULTS

We included three studies (415 participants) in people with CF aged 15 to 41 years over a 12-month period. One was a multicentre RCT, whilst two were single-centre RCTs.  The three studies were mostly similar in their risk of bias, having low or unclear risk of selection bias but a high risk of detection bias, due to the unblinded design of these studies. The studies used a variety of digital technologies to monitor symptoms such as a digital symptom diary either with or without home spirometry monitoring. As the trials only included adults and older children, we are not certain that the results would apply to younger children. One of our primary outcomes was to assess time to detection of pulmonary exacerbation and number of pulmonary exacerbations identified between the intervention and routine care groups. We were largely unable to pool results in a meta-analysis due to the variety of methodologies and ways of reporting data. Two studies noted a shorter time to detection of exacerbations in the intervention group and one of these also reported that the intervention group had a shorter time to first exacerbation (hazard ratio for time to first exacerbation 1.45, 95% confidence interval (CI) 1.09 to 1.93), whilst a further study reported a shorter time to detection of exacerbations in the intervention group requiring oral or IV antibiotics compared to the control group (median: 70 (interquartile range (IQR) 123) days with intervention versus 141 (IQR 140) days with control; P = 0.02). However, all three studies were concordant in finding no probable effect on spirometry in the intervention groups when compared with their routine care groups over a 12-month period.  We found that there is probably no difference between groups with regard to QoL scores across most domains except for Weight and Body Image, which favoured the usual care group. There is also probably no difference in the number of days of additional IV antibiotics needed or newly detected pathogens. No studies reported serious adverse events directly linked to the intervention and one study reported their smartphone application was generally well received.

AUTHORS' CONCLUSIONS

Pulmonary exacerbations are universally accepted to be detrimental to progression of CF-related lung disease, therefore, it is intuitive that early detection and intervention would help to improve outcomes. Digital technology provides an opportunity to detect physiological and symptomatic changes to identify exacerbations early.  Our review found that digital technologies based on recording physiological change (spirometry) and symptoms probably allow earlier identification of exacerbations as a group. However, this may not reduce the number of exacerbations warranting IV antibiotics and there is probably no effect on lung function. This may be partly due to inconsistent definitions of pulmonary exacerbations and discrepancy in the management strategies for pulmonary exacerbations. Overall, the intervention may make little or no difference to QoL scores.  The adherence to and uptake of digital technologies, especially those which include physiological measurements, are not well sustained and the costs of these need to be balanced against the clinical efficacy.

Psychological interventions for improving adherence to inhaled therapies in people with cystic fibrosis

BACKGROUND

Adherence to treatment, including inhaled therapies, is low in people with cystic fibrosis (CF). Although psychological interventions for improving adherence to inhaled therapies in people with CF have been developed, no previous published systematic review has evaluated the evidence for efficacy of these interventions.

OBJECTIVES

The primary objective of the review was to assess the efficacy of psychological interventions for improving adherence to inhaled therapies in people with cystic fibrosis (CF). The secondary objective was to establish the most effective components, or behaviour change techniques (BCTs), used in these interventions.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis Trials Register, which is compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched databases (PubMed; PsycINFO; EBSCO; Scopus; OpenGrey), trials registries (World Health Organization International Clinical Trials Registry Platform; US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov), and the reference lists of relevant articles and reviews, with no restrictions on language, year or publication status. Date of search: 7 August 2022.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing different types of psychological interventions for improving adherence to inhaled therapies in people with CF of any age, or comparing psychological interventions with usual care. We included quasi-RCTs if we could reasonably assume that the baseline characteristics were similar in both groups.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility and completed data extraction, risk of bias assessments, and BCT coding (using the BCT Taxonomy v1) for all included trials. We resolved any discrepancies by discussion, or by consultation with a third review author as necessary. We assessed the certainty of the evidence using GRADE.

MAIN RESULTS

We included 10 trials (1642 participants) in the review (children and adolescents in four trials; adults in five trials; and children and adults in one trial). Nine trials compared a psychological intervention with usual care; we could combine data from some of these in a number of quantitative analyses. One trial compared a psychological intervention with an active comparator (education plus problem-solving (EPS)). We identified five ongoing trials. Psychological interventions were generally multi-component and complex, containing an average of 9.6 BCTs (range 1 to 28). The two most commonly used BCTs included 'problem-solving' and 'instruction on how to perform the behaviour'. Interventions varied in their type, content and mode of delivery. They included a problem-solving intervention; a paper-based self-management workbook; a telehealth intervention; a group training programme; a digital intervention comprising medication reminders and lung function self-monitoring; a life-coaching intervention; a motivational interviewing (MI) intervention; a brief MI intervention (behaviour change counselling); and a digital intervention combined with behaviour change sessions. Intervention duration ranged from 10 weeks to 12 months. Assessment time points ranged from six to eight weeks up to 23 months. Psychological interventions compared with usual care We report data here for the 'over six months and up to 12 months' time point. We found that psychological interventions probably improve adherence to inhaled therapies (primary outcome) in people with CF compared with usual care (mean difference (MD) 9.5, 95% confidence interval (CI) 8.60 to 10.40; 1 study, 588 participants; moderate-certainty evidence). There was no evidence of a difference between groups in our second primary outcome, treatment-related adverse events: anxiety (MD 0.30, 95% CI -0.40 to 1.00; 1 study, 535 participants), or depression (MD -0.10, 95% CI -0.80 to 0.60; 1 study, 534 participants), although this was low-certainty evidence. For our secondary outcomes, there was no evidence of a difference between groups in terms of lung function (forced expiratory volume in one second (FEV1) % predicted MD 1.40, 95% CI -0.20 to 3.00; 1 study, 556 participants; moderate-certainty evidence); number of pulmonary exacerbations (adjusted rate ratio 0.96, 95% CI 0.83 to 1.11; 1 study, 607 participants; moderate-certainty evidence); or respiratory symptoms (MD 0.70, 95% CI -2.40 to 3.80; 1 study, 534 participants; low-certainty evidence). However, psychological interventions may improve treatment burden (MD 3.90, 95% CI 1.20 to 6.60; 1 study, 539 participants; low-certainty evidence). The overall certainty of the evidence ranged from low to moderate across these outcomes. Reasons for downgrading included indirectness (current evidence included adults only whereas our review question was broader and focused on people of any age) and lack of blinding of outcome assessors. Psychological interventions compared with an active comparator For this comparison the overall certainty of evidence was very low, based on one trial (n = 128) comparing an MI intervention to EPS for 12 months. We are uncertain whether an MI intervention, compared with EPS, improves adherence to inhaled therapies, lung function, or quality of life in people with CF, or whether there is an effect on pulmonary exacerbations. The included trial for this comparison did not report on treatment-related adverse events (anxiety and depression). We downgraded all reported outcomes due to small participant numbers, indirectness (trials included only adults), and unclear risk of bias (e.g. selection and attrition bias).

AUTHORS' CONCLUSIONS

Due to the limited quantity of trials included in this review, as well as the clinical and methodological heterogeneity, it was not possible to identify an overall intervention effect using meta-analysis. Some moderate-certainty evidence suggests that psychological interventions (compared with usual care) probably improve adherence to inhaled therapies in people with CF, without increasing treatment-related adverse events, anxiety and depression (low-certainty evidence). In future review updates (with ongoing trial results included), we hope to be able to establish the most effective BCTs (or 'active ingredients') of interventions for improving adherence to inhaled therapies in people with CF. Wherever possible, investigators should make use of the most objective measures of adherence available (e.g. data-logging nebulisers) to accurately determine intervention effects. Outcome reporting needs to be improved to enable combining or separation of measures as appropriate. Likewise, trial reporting needs to include details of intervention content (e.g. BCTs used); duration; intensity; and fidelity. Large trials with a longer follow-up period (e.g. 12 months) are needed in children with CF. Additionally, more research is needed to determine how to support adherence in 'under-served' CF populations.

The CFHealthHub Learning Health System: Using Real-Time Adherence Data to Support a Community of Practice to Deliver Continuous Improvement in an Archetypal Long-Term Condition

CFHealthHub is a learning health system active in over 50% of adult CF Centres in England, supporting people with CF to develop habits of self-care around adherence to preventative inhaled therapy. This is achieved through the delivery of a behaviour change intervention, alongside collection of objective adherence data. As is common to long-term conditions, adherence to prescribed therapy is low, despite clear evidence of beneficial long-term impact on outcomes. This article explains how CFHealthHub is underpinned by coherent conceptual frameworks. We discuss how application of implementation and quality improvement strategies has facilitated CFHealthHub's progression from a pilot study to a large, randomised control trial and now to a learning health system, becoming embedded within routine care. CFHealthHub is now able to support real-time health technology assessments, quality improvement and research trials and is in the process of being implemented in routine clinical care across participating centres.

Modelling Successful Self-Management in Adults With Cystic Fibrosis: Vicarious Self-Efficacy From Videos of ‘People Like Me’

Background

Self-efficacy is an important determinant of treatment adherence, and peer modelling of success can provide vicarious self-efficacy. A series of patient stories (‘talking heads’ videos) were developed with people with cystic fibrosis (CF) as part of the CFHealthHub multi-component adherence intervention, aiming to demonstrate success with daily therapy in ‘people like me’.

Methodology

One-to-one semi-structured interviews exploring patients’ experiences, barriers and facilitators of nebuliser adherence were audio and video-recorded between October 2015 and August 2016. Interview transcripts were reviewed to identify descriptions of problem-solving and sustained treatment success. Positive stories potentially providing vicarious descriptions of success were selected as video clips.

Results

In total, 14 adults with CF were recruited from five UK CF centres. Each participant contributed a median of five (interquartile range: 3-6) video clips, and a total of 57 unique clips were uploaded onto the CFHealthHub digital platform. Nine of those clips spanned two categories, hence, there were 66 clips across 16 categories.

Conclusions

The videos were well received though some adults were concerned that comparisons with peers might create anxiety by highlighting the possibility of future decline or current relative underperformance. It is important to sensitively support choice when providing resources aiming to increase vicarious self-efficacy. Our experience may guide the development of similar videos for people with other long-term conditions.

An intervention to support adherence to inhaled medication in adults with cystic fibrosis: the ACtiF research programme including RCT

Background

People with cystic fibrosis frequently have low levels of adherence to inhaled medications.

Objectives

The objectives were to develop and evaluate an intervention for adults with cystic fibrosis to improve adherence to their inhaled medication.

Design

We used agile software methods to develop an online platform. We used mixed methods to develop a behaviour change intervention for delivery by an interventionist. These were integrated to become the CFHealthHub intervention. We undertook a feasibility study consisting of a pilot randomised controlled trial and process evaluation in two cystic fibrosis centres. We evaluated the intervention using an open-label, parallel-group randomised controlled trial with usual care as the control. Participants were randomised in a 1 : 1 ratio to intervention or usual care. Usual care consisted of clinic visits every 3 months. We undertook a process evaluation alongside the randomised controlled trial, including a fidelity study, a qualitative interview study and a mediation analysis. We undertook a health economic analysis using both a within-trial and model-based analysis.

Setting

The randomised controlled trial took place in 19 UK cystic fibrosis centres.

Participants

Participants were people aged ≥ 16 years with cystic fibrosis, on the cystic fibrosis registry, not post lung transplant or on the active transplant list, who were able to consent and not using dry-powder inhalers.

Intervention

People with cystic fibrosis used a nebuliser with electronic monitoring capabilities. This transferred data automatically to a digital platform. People with cystic fibrosis and clinicians could monitor adherence using these data, including through a mobile application (app). CFHealthHub displayed graphs of adherence data as well as educational and problem-solving information. A trained interventionist helped people with cystic fibrosis to address their adherence.

Main outcome measures

Randomised controlled trial – adjusted incidence rate ratio of pulmonary exacerbations meeting the modified Fuchs criteria over a 12-month follow-up period (primary outcome); change in percentage adherence; and per cent predicted forced expiratory volume in 1 second (key secondary outcomes). Process evaluation – percentage fidelity to intervention delivery, and participant and interventionist perceptions of the intervention. Economic modelling – incremental cost per quality-adjusted life-year gained.

Results

Randomised controlled trial – 608 participants were randomised to the intervention (n = 305) or usual care (n = 303). To our knowledge, this was the largest randomised controlled trial in cystic fibrosis undertaken in the UK. The adjusted rate of exacerbations per year (primary outcome) was 1.63 in the intervention and 1.77 in the usual-care arm (incidence rate ratio 0.96, 95% confidence interval 0.83 to 1.12; p = 0.638) after adjustment for covariates. The adjusted difference in mean weekly normative adherence was 9.5% (95% confidence interval 8.6% to 10.4%) across 1 year, favouring the intervention. Adjusted mean difference in forced expiratory volume in 1 second (per cent) predicted at 12 months was 1.4% (95% confidence interval –0.2% to 3.0%). No adverse events were related to the intervention. Process evaluation – fidelity of intervention delivery was high, the intervention was acceptable to people with cystic fibrosis, participants engaged with the intervention [287/305 (94%) attended the first intervention visit], expected mechanisms of action were identified and contextual factors varied between randomised controlled trial sites. Qualitative interviews with 22 people with cystic fibrosis and 26 interventionists identified that people with cystic fibrosis welcomed the objective adherence data as proof of actions to self and others, and valued the relationship that they built with the interventionists. Economic modelling – the within-trial analysis suggests that the intervention generated 0.01 additional quality-adjusted life-years at an additional cost of £865.91 per patient, leading to an incremental cost-effectiveness ratio of £71,136 per quality-adjusted life-year gained. This should be interpreted with caution owing to the short time horizon. The health economic model suggests that the intervention is expected to generate 0.17 additional quality-adjusted life-years and cost savings of £1790 over a lifetime (70-year) horizon; hence, the intervention is expected to dominate usual care. Assuming a willingness-to-pay threshold of £20,000 per quality-adjusted life-year gained, the probability that the intervention generates more net benefit than usual care is 0.89. The model results are dependent on assumptions regarding the duration over which costs and effects of the intervention apply, the impact of the intervention on forced expiratory volume in 1 second (per cent) predicted and the relationship between increased adherence and drug-prescribing levels.

Limitations

Number of exacerbations is a sensitive and valid measure of clinical change used in many trials. However, data collection of this outcome in this context was challenging and could have been subject to bias. It was not possible to measure baseline adherence accurately. It was not possible to quantify the impact of the intervention on the number of packs of medicines prescribed.

Conclusions

We developed a feasible and acceptable intervention that was delivered to fidelity in the randomised controlled trial. We observed no statistically significant difference in the primary outcome of exacerbation rates over 12 months. We observed an increase in normative adherence levels in a disease where adherence levels are low. The magnitude of the increase in adherence may not have been large enough to affect exacerbations.

Future work

Given the non-significant difference in the primary outcome, further research is required to explore why an increase in objective normative adherence did not reduce exacerbations and to develop interventions that reduce exacerbations.

Trial registration

Work package 3.1: Current Controlled Trials ISRCTN13076797. Work packages 3.2 and 3.3: Current Controlled Trials ISRCTN55504164.

Funding

This project was funded by the National Institute for Health Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 9, No. 11. See the NIHR Journals Library website for further project information.