Search strategy

Searches for economic studies were run on MEDLINE, EMBASE via Ovid and NHS Economic Evaluation Database using, where appropriate, relevant terms for economic studies along with terms for clinical populations. Examples of these strategies can be found in Appendix 1. These searches were supplemented with any further economic evaluations and cost studies identified during screening of the search yield in the clinical effectiveness review.

Study selection

All records were screened by two reviewers independently, and copies of potentially relevant articles were obtained for scrutiny against the full selection criteria, with any disagreements resolved by discussion. The inclusion criteria were the same as those for the clinical effectiveness review except that the study designs were full economic evaluations, partial economic evaluations and cost-effectiveness analyses alongside trials and economic modelling studies.

Data extraction and quality assessment strategy

Data on the following, where available, were extracted from included studies by one reviewer and checked by another:

• study characteristics, such as study question, form of economic analysis, population, interventions, comparators, perspective, time horizon and form of modelling used
• clinical effectiveness and cost parameters, such as effectiveness data, health state valuations (utilities), resource-use data, unit-cost data, price year, discounting and key assumptions
• results and sensitivity analyses.

Studies were to be quality-assessed using the Drummond checklist¹³² for economic evaluations and the checklist by Philips¹³³ for model-based analyses.

Summary of included studies

Both included studies conducted a cost analysis alongside a clinical study of domiciliary NIV in COPD patients.^40,134 Each study met at least eight of the 10 Drummond and Jefferson quality-assessment criteria (see Appendix 11).¹³² Neither study was sponsored by industry, although some potential conflicts of interested were declared by Tuggey et al. (2003).⁴⁰ The characteristics and main results of each study are summarised in Table 19.

TABLE 19

Summary of published economic evaluations

Tuggey et al. (2003)

Tuggey et al.’s (2003)⁴⁰ cost analysis was based on a before-and-after study of 13 patients offered domiciliary NIV in one UK hospital between 1995 and 2000. Patients were started on NIV if they had a history of recurrent COPD-related hospital admissions (mean of five per year) and had demonstrated prior tolerance of NIV during treatment of an acute exacerbation. As the clinical study enrolled a highly select group of COPD patients, the results are not necessarily transferable to a wider COPD population.

Outcomes were collected from case notes and as a result are potentially biased because of the risk of reporting errors. The study found a statistically significant reduction in admissions, which was the primary measure of effect considered in the subsequent cost analysis. Costs were collected retrospectively and the cost analysis was conducted from a hospital perspective, and thus did not include costs incurred by patients, carers, primary care or the wider society. Costs included acute and conventional hospital admissions, intensive care treatment, outpatient appointments and the cost of domiciliary NIV. The cost of trialled patients on NIV in hospital was not considered as an additional cost, as this was considered part of usual care.

A number of assumptions regarding the costs of acute and domiciliary NIV were drawn from Plant et al. (2003),¹³⁵ a published economic evaluation of NIV for managing acute exacerbation in COPD patients. In this analysis the provision of domiciliary NIV was estimated to cost £1060 per patient per year in 2003 NHS prices. This included £570 for ventilator equipment discounted over 5 years, £224 for mask and tubing with an assumed lifespan of 8 months, £179 for a warm air humidifier with an assumed lifespan of 1 year, £28 for annual servicing and £60 for access to a respiratory nurse specialist.

The results of this analysis found domiciliary NIV in COPD patients with recurrent exacerbation, implemented at discharge, to be cost-saving, resulting in a net saving of £8254 (95% CI £4013 to £12,495) per patient per year. A one-way sensitivity analysis was conducted by varying key assumptions from baseline between the 5th and 95th centiles, and in all scenarios domiciliary NIV was cost-saving compared with usual care alone.

In summary, this study suggests domiciliary NIV may be cost-effective in NIV patients with a history of readmission to hospital. Caution should be taken in interpreting these results, as they are based on a very small sample size and highly select group of patients.

Clini et al. (2009)

Clini et al. (2009)¹³⁴ presented the results of an Italian cost analysis, conducted alongside a RCT of domiciliary NIV, where 77 patients were followed up for 2 years. Patients with stable COPD, with a prior prescription of LTOT, were enrolled on the trial and randomised to NIV or usual care alone.

This cost analysis applied the mean reduction in hospital admissions and length of stay derived from the RCT. It should, however, be noted that, while the outcomes found in the RCT were in favour of NIV, the results applied were not statistically significant. The resources considered in the analysis included hospital admissions, drug therapy, LTOT and domiciliary NIV equipment and training. Neither the other primary-care resources and costs incurred by patients and their families nor the additional hospital and set-up costs to familiarise patients with NIV were included.

The study estimated the cost of domiciliary NIV to be €160 per month or €1920 per year based on 2008 prices. This estimate was based on a contract with a regional health-care provider and included the provision of equipment, a Respironics BiPAP^® ST-30 (Murrysville, PA, USA) device and warm air humidifier, as well as tubing and masks replaced every 6 months. The results suggest that the addition of domiciliary NIV to LTOT results in a similar cost per patient per day of €23.73 ± €16.18, compared with €21.42 ± €20.38 in the group with LTOT alone, from which the authors concluded that domiciliary NIV was likely to be cost-neutral, as the additional costs were offset by savings from reduced hospital admissions and shorter hospital stays.

In summary, this study suggests that domiciliary NIV may be cost-neutral in stable COPD patients. However, as this study was conducted in Italy, the costs and outcomes are not directly transferable to UK patients. The results should also be considered cautiously because of uncertainty around the effect.

Commentary on excluded studies

Two studies excluded from this review warrant comment.

Criner et al. (1995)¹³⁶ conducted a retrospective cost analysis of providing NIV to patients admitted to a ventilator rehabilitation unit for moderately severe respiratory failure in the USA. There was some ambiguity as to whether or not this met the inclusion criterion, as it was unclear if patients were discharged with NIV for home use. On balance, the decision was made to exclude the study, as it appeared to primarily assess the effect of NIV delivered in an acute setting. This study demonstrated the interdependence between acute and domiciliary NIV services when considering costs and outcomes.

Chandra et al. (2012)¹³⁷ published a Markov model developed as part of a series of papers to evaluate the effectiveness and cost-effectiveness of interventions in COPD populations sponsored by the Medical Advisory Secretariat, Canada. NIV in stable COPD patients was included in this series and the authors documented their intent to conduct a clinical review and economic evaluation.¹³⁷ However, after conducting the clinical review, they concluded that there was no evidence that domiciliary NIV was effective in COPD patients and thus did not conduct an economic analysis.