Dynamic modulation of spatially structured polarization fields for real-time control of ultrafast laser-material interactions

The polarization state of an ultrafast laser is dynamically controlled using two Spatial Light Modulators and additional waveplates. Consequently, four states of polarization, linear horizontal and vertical, radial and azimuthal, all with a ring intensity distribution, were dynamically switched at a frequency ν = 12.5 Hz while synchronized with a motion control system. This technique, demonstrated here for the first time, enables a remarkable level of real-time control of the properties of light waves and applied to real-time surface patterning, shows that highly controlled nanostructuring is possible. Laser ablation of Induced Periodic Surface Structures is used to directly verify the state of polarization at the focal plane.

What is the clinical effectiveness and cost-effectiveness of using drugs in treating obese patients in primary care? A systematic review

BACKGROUND

Obesity [defined as a body mass index (BMI) ≥ 30 kg/m(2)] represents a considerable public health problem and is associated with a significant range of comorbidities and an increased mortality risk. The primary aim of the management of obesity is to achieve weight reduction in the interests of health. For obese patients who cannot achieve or maintain a healthy weight by non-pharmacological means, drug therapy is recommended in combination with non-pharmacological interventions such as dietary modifications and exercise.

OBJECTIVE

To evaluate the clinical effectiveness and cost-effectiveness of three pharmacological interventions in obese patients.

DATA SOURCES

Clinical effectiveness data used in the meta-analysis were sourced from articles identified in a systematic review of the literature. Data used to inform transitions to obesity-related comorbidities were derived from the General Practice Research Database (GPRD). The results of the meta-analysis and GPRD analyses informed the economic model supplemented by data from the Health Survey for England and other UK-specific data sourced from the literature.

REVIEW METHODS

A systematic literature review was conducted of the clinical effectiveness and cost-effectiveness of orlistat, sibutramine and rimonabant within their licensed indications for the treatment of obese patients. Electronic bibliographic databases including MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, EMBASE, The Cochrane Library databases and Cumulative Index to Nursing and Allied Health Literature (CINAHL) were searched in January 2009, and the reference lists of relevant articles were checked. Studies were included if they compared orlistat, sibutramine or rimonabant with lifestyle and/or exercise advice (standard care), placebo or metformin.

RESULTS

Overall, 94 studies involving 24,808 individuals were included in the clinical meta-analysis. Eighty-three trials included data on weight change, 41 included data on BMI change and 45 and 36 studies reported on 5% and 10% body weight loss, respectively. Overall, the results show that the active drug interventions are all effective at reducing weight and BMI compared with placebo. In the case of sibutramine, the higher dose (15 mg) resulted in a greater reduction than the lower dose (10 mg). Generally, the data quality of the trials included was low with poor reporting of standard errors and standard deviations. Results from the BMI risk models derived from the GPRD showed consistent increases in risk with increasing BMI. Adjustments for key confounders, such as age, sex and smoking status, were found to be statistically significant at the 5% level, in all risk models. Applying linear models to estimate BMI trajectories, for the diabetic cohort, an average increase in BMI of 0.040 per year for both men and women was observed. The non-diabetic cohort model showed an increase in BMI of 0.175 per year for women and 0.145 per year for men. The results of the cost-effectiveness analyses suggest that sibutramine 15 mg dominates the other three active interventions and the net benefit analyses show that sibutramine 15 mg is the most cost-effective alternative for thresholds > £2000 per quality-adjusted life-year (QALY). However, both sibutramine and rimonabant have been withdrawn because of safety concerns relating to potential treatment-induced fatal adverse events. If the proportion of patients who experienced a fatal adverse event was > 1.8% (1.5%, 1.0%) for sibutramine 15 mg (sibutramine 10 mg, rimonabant) the treatment would not be considered cost-effective when using a threshold of £20,000 per QALY.

LIMITATIONS

The clinical review did not include all possible lifestyle comparators, with the inclusion limited to only those trials included one of the active drug interventions. We also excluded all studies not reported in English. Although the clinical review included data from 94 studies, the quality of data was generally low, particularly in terms of the reporting of standard deviation. There was also inconsistency between the results of the mixed-treatment comparison (MTC) and the pair-wise analyses.

CONCLUSION

The MTC of anti-obesity treatments shows that all the active treatments are effective at reducing weight and BMI. The economic results show that, compared with placebo, the treatments are all cost-effective when using a threshold of £20,000 per QALY, and, within the limitations of the data available, sibutramine 15 mg dominates the other three interventions. This work has highlighted many areas of methodological research that could be explored, including assessing inconsistencies within a network to determine differences between the results of pair-wise and MTC analyses; the use of meta-regression methods to look for effect modifiers; exploring the effect of local publication bias; and the use of joint models to analyse the repeated measures of BMI and the time-to-event processes simultaneously.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

A systematic review and mixed treatment comparison of pharmacological interventions for the treatment of obesity

The study aims to compare anti-obesity interventions in a single evidence synthesis framework. Electronic databases were searched for randomized controlled trials of orlistat, rimonabant or sibutramine reporting weight or body mass index (BMI) change from baseline at 3, 6 or 12 months. A mixed treatment comparison was used to combine direct and indirect trial evidence. Ninety-four studies involving 24,808 individuals were included; 83 trials included data on weight change and 41 on BMI change. All results are in comparison with placebo. The active drugs were all effective at reducing weight and BMI. At 3 months, orlistat reduced weight by -2.65 kg (95% credibility interval -4.00 kg, -1.31 kg). For sibutramine, 15 mg gave a greater reduction than 10 mg at 12 months, -6.35 kg versus -5.42 kg, respectively. Rimonabant reduced weight by -11.23 kg at 3 months and -4.55 kg at 12 months. Lifestyle advice alone also reduced weight at 6 and 12 months, but was less effective than the pharmacological interventions. In conclusion, modest weight reductions were seen for all pharmacological interventions. Those interventions which have now been withdrawn from use (sibutramine and rimonabant) seem to be the most effective, implying that there may be a place in clinical practice for similar drugs if side effects could be avoided.

Sotrastaurin, a novel small molecule inhibiting protein-kinase C: randomized phase II study in renal transplant recipients

Sotrastaurin, a selective protein-kinase-C inhibitor, blocks early T-cell activation through a calcineurin-independent mechanism. In this study, de novo renal transplant recipients with immediate graft function were randomized 1:2 to tacrolimus (control, n = 44) or sotrastaurin (300 mg b.i.d.; n = 81). All patients received basiliximab, mycophenolic acid (MPA) and steroids. The primary endpoint was the composite of treated biopsy-proven acute rejection (BPAR), graft loss, death or lost to follow-up at month 3. The main safety assessment was estimated glomerular filtration rate (eGFR); modification of diet in renal disease (MDRD) at month 3. Composite efficacy failure at month 3 was higher for the sotrastaurin versus control regimen (25.7% vs. 4.5%, p = 0.001), driven by higher BPAR rates (23.6% vs. 4.5%, p = 0.003), which led to early study termination. Median (± standard deviation [SD]) eGFR was higher for sotrastaurin versus control at all timepoints from day 7 (month 3: 59.0 ± 22.3 vs. 49.5 ± 17.7 mL/min/1.73 m(2) , p = 0.006). The most common adverse events were gastrointestinal disorders (control: 63.6%; sotrastaurin: 88.9%) which led to study-medication discontinuation in two sotrastaurin patients. This study demonstrated a lower degree of efficacy but better renal function with the calcineurin-inhibitor-free regimen of sotrastaurin+MPA versus the tacrolimus-based control. Ongoing studies are evaluating alternative sotrastaurin regimens.

Etanercept, infliximab and adalimumab for the treatment of psoriatic arthritis: a systematic review and economic evaluation

BACKGROUND

Etanercept, infliximab and adalimumab are licensed in the UK for the treatment of active and progressive psoriatic arthritis (PsA) in adults who have an inadequate response to standard treatment.

OBJECTIVE

To determine the clinical effectiveness, safety and cost-effectiveness of these biologic agents in the treatment of active and progressive PsA.

DATA SOURCES

Systematic reviews were performed, with data sought from 10 electronic databases (MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Science Citation Index, Conference Proceedings Citation Index - Science, ClinicalTrials.gov, metaRegister of Current Controlled Trials, NHS Economic Evaluation Database, Health Economic Evaluations Database and EconLit) up to June 2009.

REVIEW METHODS

Full paper manuscripts of titles/abstracts considered relevant were obtained and assessed for inclusion by two reviewers according to criteria on study design, interventions, participants and outcomes. Data on study and participant characteristics, efficacy outcomes, adverse effects, costs to the health service and cost-effectiveness were extracted, along with baseline data where reported. The primary efficacy outcomes were measures of anti-inflammatory response, skin lesion response and functional status, and the safety outcome was the incidence of serious adverse events. The primary measure of cost-effectiveness was incremental cost per additional quality-adjusted life-year (QALY). Standard meta-analytic techniques were applied to efficacy data. Published cost-effectiveness studies and the economic analyses submitted to the National Institute for Health and Clinical Excellence (NICE) by the biologic manufacturers were reviewed. An economic model was developed by updating the model produced by the York Assessment Group for the previous NICE appraisal of biologics in PsA.

RESULTS

Pooled estimates of effect demonstrated a significant improvement in patients with PsA for all joint disease and functional status outcomes at 12-14 weeks' follow-up. The biologic treatment significantly reduced joint symptoms for etanercept [relative risk (RR) 2.60, 95% confidence interval (CI) 1.96 to 3.45], infliximab (RR 3.44, 95% CI 2.53 to 4.69) and adalimumab (RR 2.24, 95% CI 1.74 to 2.88), with 24-week data demonstrating maintained treatment effects. Trial data demonstrated a significant effect of all three biologics on skin disease at 12 or 24 weeks. Evidence synthesis found that infliximab appeared to be most effective across all outcomes of joint and skin disease. The response in joint disease was greater with etanercept than with adalimumab, whereas the response in skin disease was greater with adalimumab than with etanercept, although these differences are not statistically significant. Under base-case assumptions, etanercept was the most likely cost-effective strategy for patients with PsA and mild-to-moderate psoriasis if the threshold for cost-effectiveness was £20,000 or £30,000 per QALY. All biologics had a similar probability of being cost-effective for patients with PsA and moderate-to-severe psoriasis at a threshold of £20,000 per QALY.

LIMITATIONS

Limited available efficacy data and difficulty in assessing PsA activity and its response to biologic therapy.

CONCLUSIONS

The data indicated that etanercept, infliximab and adalimumab were efficacious in the treatment of PsA compared with placebo, with beneficial effects on joint symptoms, functional status and skin. Short-term data suggested that these biologic agents can delay joint disease progression and evidence to support their use in the treatment of PsA is convincing. Future research would benefit from long-term observational studies with large sample sizes of patients with PsA to demonstrate that beneficial effects are maintained, along with further monitoring of the safety profiles of the biologic agents.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

The effectiveness and cost-effectiveness of biomarkers for the prioritisation of patients awaiting coronary revascularisation: a systematic review and decision model

OBJECTIVE

To determine the effectiveness and cost-effectiveness of a range of strategies based on conventional clinical information and novel circulating biomarkers for prioritising patients with stable angina awaiting coronary artery bypass grafting (CABG).

DATA SOURCES

MEDLINE and EMBASE were searched from 1966 until 30 November 2008.

REVIEW METHODS

We carried out systematic reviews and meta-analyses of literature-based estimates of the prognostic effects of circulating biomarkers in stable coronary disease. We assessed five routinely measured biomarkers and the eight emerging (i.e. not currently routinely measured) biomarkers recommended by the European Society of Cardiology Angina guidelines. The cost-effectiveness of prioritising patients on the waiting list for CABG using circulating biomarkers was compared against a range of alternative formal approaches to prioritisation as well as no formal prioritisation. A decision-analytic model was developed to synthesise data on a range of effectiveness, resource use and value parameters necessary to determine cost-effectiveness. A total of seven strategies was evaluated in the final model.

RESULTS

We included 390 reports of biomarker effects in our review. The quality of individual study reports was variable, with evidence of small study (publication) bias and incomplete adjustment for simple clinical information such as age, sex, smoking, diabetes and obesity. The risk of cardiovascular events while on the waiting list for CABG was 3 per 10,000 patients per day within the first 90 days (184 events in 9935 patients with a mean of 59 days at risk). Risk factors associated with an increased risk, and included in the basic risk equation, were age, diabetes, heart failure, previous myocardial infarction and involvement of the left main coronary artery or three-vessel disease. The optimal strategy in terms of cost-effectiveness considerations was a prioritisation strategy employing biomarker information. Evaluating shorter maximum waiting times did not alter the conclusion that a prioritisation strategy with a risk score using estimated glomerular filtration rate (eGFR) was cost-effective. These results were robust to most alternative scenarios investigating other sources of uncertainty. However, the cost-effectiveness of the strategy using a risk score with both eGFR and C-reactive protein (CRP) was potentially sensitive to the cost of the CRP test itself (assumed to be 6 pounds in the base-case scenario).

CONCLUSIONS

Formally employing more information in the prioritisation of patients awaiting CABG appears to be a cost-effective approach and may result in improved health outcomes. The most robust results relate to a strategy employing a risk score using conventional clinical information together with a single biomarker (eGFR). The additional prognostic information conferred by collecting the more costly novel circulating biomarker CRP, singly or in combination with other biomarkers, in terms of waiting list prioritisation is unlikely to be cost-effective.

The clinical effectiveness and cost-effectiveness of enzyme replacement therapy for Gaucher's disease: a systematic review

OBJECTIVES

The aim of this review is to determine the clinical effectiveness and cost-effectiveness of enzyme replacement therapy (ERT) in the treatment of symptomatic Gaucher's disease.

DATA SOURCES

Major electronic databases were searched from their inception to August 2003; and updated from January 2003 to July/August 2004.

REVIEW METHODS

Databases were searched for studies that met the criteria and selected data were extracted and evaluated. Studies were assessed for their relevance to the UK context and the review objective. The bibliographic databases were also searched to identify existing cost studies, economic evaluations and models. A Markov decision model was constructed based on patients moving between states defined by the modified Severity Score Index (SSI). Most of the parameters were derived from the published literature. ERT was assumed to restore patients to full health in the base case.

RESULTS

Sixty-three studies were included, all suggestive of benefit with ERT. However, the way in which the effects translate into patient well-being and survival or the need for services and resources has not been reliably estimated. Quality of life improvements with ERT have been reported. Nonetheless, studies based on the Short Form 36 (SF-36) indicate that patients treated with ERT continue to have reduced health-related quality of life (HRQoL) compared with the general population. No study attached utility values to quality of life measures for ERT-treated patients. Thirty-one studies relevant to the natural history of the disease were found. Sixteen looked at multiple clinical characteristics of a cohort of patients with type I Gaucher's disease. There was considerable within-study and between-study heterogeneity, but all showed that Gaucher's disease was a progressive condition. Some suggested that the disease may become more indolent in adulthood; however, studies were discrepant on this point. Most disease is diagnosed in adulthood, although about one-quarter presented in childhood, these patients having the most severe symptoms and greatest rate of progression. Modelling of natural history was undertaken using the five papers that reported the SSI for each patient, along with patient-level data on age, age at diagnosis, splenectomy status and genotype, to address the question of whether disease stabilises in adulthood and the degree of correlation between phenotype and genotype. Analysis of the available data suggested that disease progression is likely to slow markedly in adulthood and that genotype is a useful predictor of clinical expression of the disease. Five studies looked at quality of life. Data on this topic were also obtained from the registries. The evidence suggests that the vast majority of the clinical characteristics of type I Gaucher's disease have little impact on subjective HRQoL and that therefore for the majority of people with type I Gaucher's disease this may not be a severe condition. Bone and skeletal symptoms contribute most to the morbidity of the disease and can lead to severe pain and immobility. The mean cost per patient treated was approximately pounds sterling 86,000 per annum in England and Wales. The cost per patient varied considerably by dose. Four existing economic evaluations were found, all of which calculated a very high cost per quality-adjusted life-year (QALY). Using the Markov decision model, ERT was assumed to restore patients to full health in the base case. The estimated incremental cost per QALY [incremental cost-effectiveness ratio (ICER)] in the base case ranged from pounds sterling 380,000 to pounds sterling 476,000 per QALY, depending on genotype. Univariate sensitivity analyses examined ERT not restoring full health, more severe disease progression in the untreated cohort, and only treating the most severely affected patients. These produced ICERs of approximately pounds sterling 1.4 million, pounds sterling 296,000 and pounds sterling 275,000 per QALY, respectively. The base-case unit cost of the drug is pounds sterling 2.975. The unit cost would have had to be reduced ten-fold, to pounds sterling 0.30, to obtain an ICER of pounds sterling 30,000 per QALY. At a unit cost of pounds sterling 1 the ICER would be pounds sterling 120,000 per QALY.

CONCLUSIONS

Although ERT for treating the 'average' Gaucher's disease patient exceeds the normal upper threshold for cost-effectiveness seen in NHS policy decisions by over ten-fold, some argue that since orphan drug legislation encouraged the manufacture of Cerezyme, and Gaucher's disease can be defined as an orphan disease, the NHS has little option but to provide it, despite its great expense. More information is required before the generalisability of the findings can be determined. Although data from the UK have been used wherever possible, these were very thin indeed. Nonetheless, even large errors in estimates of the distribution of genotype, genotype--phenotype associations, effectiveness and numbers of patients will not reduce the ICER to anywhere near the upper level of treatments usually considered cost-effective. Further research could help to clarify the many uncertainties that exist. However, although doing so will be of clinical interest, it is questionable whether, within the current pricing environment, such research would have any substantive impact on policy decisions. It is highly improbable that, whatever the findings of such research, the ICER could be brought down by the orders of magnitude required to make ERT an efficient use of health service resources. (The possible exception to this would be investigating the most efficient alternative treatment strategies for using ERT in a paediatric population only.) Moreover, if under equity considerations for orphan diseases the NHS feels it is important to provide this drug, regardless of its cost-effectiveness, then refining the precision of the ICER estimate also becomes superfluous.

Optimizing a canine survival model of orthotopic lung transplantation

INTRODUCTION

While acute models of orthotopic lung transplantation have been described in dogs, the technical considerations of developing a survival model in this species have not been elaborated. Herein, we describe optimization of a canine survival model of orthotopic lung transplantation.

METHODS

Protocols of orthotopic left lung transplantation and single lung ventilation were established in acute experiments (n=9). Four dogs, serving as controls, received autologous, orthotopic lung transplants. Allogeneic transplants were performed in 16 DLA-identical and 16 DLA-mismatched unrelated recipient dogs. Selective right lung ventilation was utilized in all animals. A Malecot tube was left in the pleural space connected to a Heimlich valve for up to 24 hours. To date, animals have been followed up to 24 months by chest radiography, pulmonary function tests, bronchoscopy with lavage, and open biopsies.

RESULTS

Long-term survival was achieved in 34/36 animals. Two recipients died intraoperatively secondary to cardiac arrest. All animals were extubated on the operating table, and in all cases the chest tube was removed within 24 hours. Major complications included thrombosis of the pulmonary artery and subcritical stenosis of bronchial anastamosis. One recipient underwent successful treatment of a small bowel intussusception.

CONCLUSIONS

We report our experience in developing a survival canine model of orthotopic single lung transplantation. While short-term survival following canine lung transplantation is achievable, we report particular considerations that facilitate animal comfort, early extubation, and lung reexpansion in the immediate postoperative period, further optimizing use of this species for experimental modeling of long-term complications after lung transplantation.

Cost-effectiveness of alternative strategies for the initial medical management of non-ST elevation acute coronary syndrome: systematic review and decision-analytical modelling

OBJECTIVES

To identify and prioritise key areas of clinical uncertainty regarding the medical management of non-ST elevation acute coronary syndrome (ACS) in current UK practice.

DATA SOURCES

Electronic databases. Consultations with clinical advisors. Postal survey of cardiologists.

REVIEW METHODS

Potential areas of important uncertainty were identified and 'decision problems' prioritised. A systematic literature review was carried out using standard methods. The constructed decision model consisted of a short-term phase that applied the results of the systematic review and a long-term phase that included relevant information from a UK observational study to extrapolate estimated costs and effects. Sensitivity analyses were undertaken to examine the dependence of the results on baseline parameters, using alternative data sources. Expected value of information analysis was undertaken to estimate the expected value of perfect information associated with the decision problem. This provided an upper bound on the monetary value associated with additional research in the area.

RESULTS

Seven current areas of clinical uncertainty (decision problems) in the drug treatment of unstable angina patients were identified. The agents concerned were clopidogrel, low molecular weight heparin, hirudin and intravenous glycoprotein antagonists (GPAs). Twelve published clinical guidelines for unstable angina or non-ST elevation ACS were identified, but few contained recommendations about the specified decision problems. The postal survey of clinicians showed that the greatest disagreement existed for the use of small molecule GPAs, and the greatest uncertainty existed for decisions relating to the use of abciximab (a large molecule GPA). Overall, decision problems concerning the GPA class of drugs were considered to be the highest priority for further study. Selected papers describing the clinical efficacy of treatment were divided into three groups, each representing an alternative strategy. The strategy involving the use of GPAs as part of the initial medical management of all non-ST elevation ACS was the optimal choice, with an incremental cost-effectiveness ratio (ICER) of 5738 pounds per quality-adjusted life-year (QALY) compared with no use of GPAs. Stochastic analysis showed that if the health service is willing to pay 10,000 pounds per additional QALY, the probability of this strategy being cost-effective was around 82%, increasing to 95% at a threshold of 50,000 pounds per QALY. A sensitivity analysis including an additional strategy of using GPAs as part of initial medical management only in patients at particular high risk (as defined by age, ST depression or diabetes) showed that this additional strategy was yet more cost-effective, with an ICER of 3996 pounds per QALY compared with no treatment with GPA. Value of information analysis suggested that there was considerable merit in additional research to reduce the level of uncertainty in the optimal decision. At a threshold of 10,000 pounds per QALY, the maximum potential value of such research in the base case was calculated as 12.7 million pounds per annum for the UK as a whole. Taking account of the greater uncertainty in the sensitivity analyses including clopidogrel, this figure was increased to approximately 50 million pounds.

CONCLUSIONS

This study suggests the use of GPAs in all non-ST elevation ACS patients as part of their initial medical management. Sensitivity analysis showed that virtually all of the benefit could be realised by treating only high-risk patients. Further clarification of the optimum role of GPAs in the UK NHS depends on the availability of further high-quality observational and trial data. Value of information analysis derived from the model suggests that a relatively large investment in such research may be worthwhile. Further research should focus on the identification of the characteristics of patients who benefit most from GPAs as part of medical management, the comparison of GPAs with clopidogrel as an adjunct to standard care, follow-up cohort studies of the costs and outcomes of high-risk non-ST elevation ACS over several years, and exploring how clinicians' decisions combine a normative evidence-based decision model with their own personal behavioural perspective.

Systematic review and economic decision modelling for the prevention and treatment of influenza A and B

OBJECTIVES

To establish the clinical and cost-effectiveness of amantadine, oseltamivir and zanamivir compared to standard care for the treatment and prevention of influenza.

DATA SOURCES

Electronic databases. Reference lists of identified articles and key publications. Relevant trials.

REVIEW METHODS

A systematic review and meta-analysis of the randomised evidence was undertaken to investigate the effectiveness of oseltamivir and zanamivir compared to standard care for treatment and prophylaxis use for influenza A and B. An additional systematic review of the effectiveness of amantadine for treatment and prophylaxis use for influenza A in children and the elderly was also undertaken. Economic decision models were constructed to examine the cost-effectiveness and cost-utility of the alternative strategies for treating and preventing influenza A and/or B. This was informed by the systematic reviews outlined above and additional sources of information where required.

RESULTS

The systematic review of the treatment of influenza found that oseltamivir reduced the median duration of symptoms in the influenza positive group by 1.38 days for the otherwise healthy adult population, 0.5 day for the high-risk population, and 1.5 days for the children population. This compared to 1.26 days, 1.99 days, and 1.3 for the similar groups for inhaled zanamivir. The systematic review of the prevention of influenza found that the relative risk reduction for oseltamivir was between approximately 75 and 90% and approximately 70 and 90% for inhaled zanamivir depending on the strategy adopted and the population under consideration. For the economic model a base case was constructed that focussed primarily on the health benefits generated by shortening the period of influenza illness. This base case found that, compared to standard care, the estimated cost per quality-adjusted life year ranged from pound 6190 to pound 31,529 for healthy adults, from pound 4535 to pound 22,502 for the 'high-risk' group, from pound 6117 to pound 30,825 for children, and from pound 5057 to pound 21,781 for the residential care elderly population. The base case model included valuations of the health effects of pneumonia (and otitis media in the children's model) based on observed rates in the trials. However it does not include the cost of hospitalisations as only very limited data was available for the effects of antivirals on hospitalisation rates. As for mortality rates, deaths from influenza were rare in trials of neuraminidase inhibitors (NIs). Therefore, suitable data on mortality were not available from these sources. As avoided hospitalisation costs and avoided mortality are potentially important we also carried out sensitivity analysis that involved extrapolating the observed reductions in pneumonias in the NI trials to hospitalisations and deaths. In all four models the cost-effectiveness of NIs is substantially improved by this extrapolation. For prophylaxis, antiviral drugs were compared with vaccination as preventative strategies. In all cases the cost-effectiveness ratios for vaccination were either low or cost-saving. In the base case the cost-effectiveness of antivirals was relatively unfavourable, there were scenarios relating to the elderly residential care model where antivirals as an additional strategy could be cost-effective.

CONCLUSIONS

The cost-effectiveness varies markedly between the intervention strategies and target populations. The estimate of cost effectiveness is also sensitive to variations in certain key parameters of the model, for example the proportion of all influenza-like illnesses that are influenza. The effectiveness literature that was used to inform the economic decision model spans many decades and hence great caution should be exercised when interpreting the results of indirect intervention comparisons from the model. Further randomised trials making direct comparisons would be valuable to verify the model's findings.