Christian Stock

CUNY Graduate Center, New York City, New York, United States

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Publications (4)21.52 Total impact

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    ABSTRACT: Clearly the benefits of a treatment must not be outweighed by the adverse effects. If researchers fail to incorporate adverse effects adequately in models, this could limit the validity of the results obtained. In the worst case, interventions that are cost-effective may be shown not to be. The aim of this research was to review current practice when incorporating adverse effects in economic models. A survey of HTA reports commissioned by the National Institute for Health Research (NIHR) Health Technology Assessment programme, published between 2004 and 2007 was conducted. All reports which investigated the clinical and cost-effectiveness of a health technology using a systematic review and an economic model framework were included. A total of eighty reports met the inclusion criteria. Of the models including adverse effects (43/80), 67 percent used a clinical adverse effects parameter, 79 percent a cost of adverse effects parameter, 86 percent used one of these, and 60 percent used both. Of the thirty-seven models that did not include adverse effects, eighteen justified this omission, most commonly lack of data; nineteen appeared to make no explicit consideration of adverse effects in the model. In many cases, poor reporting made it difficult to ascertain if there had been any consideration of adverse effects. We suggest that the findings of this survey support a call for much clearer and explicit reporting of adverse effects, or their exclusion, in decision models and for explicit recognition in future guidelines that "all relevant outcomes" should include some consideration of adverse events.
    International Journal of Technology Assessment in Health Care 07/2010; 26(3):323-9. · 1.55 Impact Factor
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    ABSTRACT: To identify methodological research on the incorporation of adverse effects in economic models and to review current practice. Major electronic databases (Cochrane Methodology Register, Health Economic Evaluations Database, NHS Economic Evaluation Database, EconLit, EMBASE, Health Management Information Consortium, IDEAS, MEDLINE and Science Citation Index) were searched from inception to September 2007. Health technology assessment (HTA) reports commissioned by the National Institute for Health Research (NIHR) HTA programme and published between 2004 and 2007 were also reviewed. The reviews of methodological research on the inclusion of adverse effects in decision models and of current practice were carried out according to standard methods. Data were summarised in a narrative synthesis. Of the 719 potentially relevant references in the methodological research review, five met the inclusion criteria; however, they contained little information of direct relevance to the incorporation of adverse effects in models. Of the 194 HTA monographs published from 2004 to 2007, 80 were reviewed, covering a range of research and therapeutic areas. In total, 85% of the reports included adverse effects in the clinical effectiveness review and 54% of the decision models included adverse effects in the model; 49% included adverse effects in the clinical review and model. The link between adverse effects in the clinical review and model was generally weak; only 3/80 (< 4%) used the results of a meta-analysis from the systematic review of clinical effectiveness and none used only data from the review without further manipulation. Of the models including adverse effects, 67% used a clinical adverse effects parameter, 79% used a cost of adverse effects parameter, 86% used one of these and 60% used both. Most models (83%) used utilities, but only two (2.5%) used solely utilities to incorporate adverse effects and were explicit that the utility captured relevant adverse effects; 53% of those models that included utilities derived them from patients on treatment and could therefore be interpreted as capturing adverse effects. In total, 30% of the models that included adverse effects used withdrawals related to drug toxicity and therefore might be interpreted as using withdrawals to capture adverse effects, but this was explicitly stated in only three reports. Of the 37 models that did not include adverse effects, 18 provided justification for this omission, most commonly lack of data; 19 appeared to make no explicit consideration of adverse effects in the model. There is an implicit assumption within modelling guidance that adverse effects are very important but there is a lack of clarity regarding how they should be dealt with and considered in modelling. In many cases a lack of clear reporting in the HTAs made it extremely difficult to ascertain what had actually been carried out in consideration of adverse effects. The main recommendation is for much clearer and explicit reporting of adverse effects, or their exclusion, in decision models and for explicit recognition in future guidelines that 'all relevant outcomes' should include some consideration of adverse events.
    Health technology assessment (Winchester, England). 12/2009; 13(62):1-71, 97-181, iii.
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    ABSTRACT: To evaluate the clinical effectiveness (including adverse events) and cost-effectiveness of antivirals for the treatment of naturally acquired influenza for 'at-risk' and otherwise healthy populations. Eleven electronic databases (MEDLINE, EMBASE, Cumulative Index to Nursing and Allied Health Literature, Pascal, Science Citation Index, BIOSIS, Latin American and Caribbean Health Sciences, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Database of Abstracts of Reviews of Effects, and Health Technology Assessment Database) were searched from October 2001 to November 2007. A supplementary search was undertaken in June 2008 for information relating to drug resistance during the 2007-8 influenza season. Systematic reviews of the evidence on the clinical effectiveness and cost-effectiveness of antivirals for the treatment of influenza were undertaken. Twenty-nine randomised controlled trials comparing antivirals with each other, placebo, or best symptomatic care were included in the evaluation of clinical effectiveness in patients presenting with an influenza-like illness (ILI). Primary outcomes were measures of symptom duration (median time to alleviation of symptoms and median time to return to normal activity). Incidence of complications, mortality, hospitalisations, antibiotic use (as a surrogate for complications) and adverse events was also assessed. In addition, an independent decision model was developed to evaluate the cost-effectiveness of antiviral treatment from the perspective of the UK NHS. Amantadine was excluded at an early stage, owing to a lack of any new trials that met the inclusion criteria and the limitations of the existing evidence. The review therefore focused on the neuraminidase inhibitors (NIs) oseltamivir and zanamivir, both of which were found to be effective in reducing symptom duration (zanamavir by 0.5-1.0 days and oseltamivir by 0.5-1.5 days). However, the effect sizes were often small and unlikely to be clinically significant in many cases, particularly in healthy adults. For the at-risk subgroups, effect sizes for differences in symptom duration were generally larger, and potentially more clinically significant, than those seen in healthy adults (median duration of symptoms reduced by 1-2 days with zanamivir and 0.50-0.75 days with oseltamivir). However, there was greater uncertainty around these results, with estimates often failing to reach statistical significance. The most consistent data and strongest evidence related to antibiotic use, with both zanamivir and oseltamivir resulting in statistically significant reductions in antibiotic use. In general, the estimates from the cost-effectiveness model were more favourable in at-risk populations (including adults and children with comorbid conditions and the elderly) compared with otherwise healthy populations. Zanamivir was the optimal NI treatment in each of the at-risk populations considered, and oseltamivir was optimal for healthy populations (both adults and children). The clinical effectiveness data for population subgroups used to inform the multiparameter evidence synthesis and cost-effectiveness modelling were, in places, limited and this should be borne in mind when interpreting the findings of this review. Trials were often not designed to determine clinical effectiveness in population subgroups and hence, although the direction of effect was clear, estimates of differences in symptom duration tended to be subject to greater uncertainty in subgroups. Despite some concerns, the use of NIs in at-risk populations appeared to be a cost-effective approach for the treatment of influenza. Well-designed observational studies might also be considered to evaluate the clinical course of influenza in terms of complications, hospitalisation, mortality and quality of life, as well as the impact of NIs.
    Health technology assessment (Winchester, England). 11/2009; 13(58):1-265, iii-iv.
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    ABSTRACT: In publicly funded health systems with finite resources, management decisions are based on assessments of clinical effectiveness and cost-effectiveness. The UK National Institute for Health and Clinical Excellence commissioned a systematic review to inform their 2009 update to guidance on the use of antiviral drugs for the treatment of influenza. We searched databases for studies of the use of neuraminidase inhibitors for the treatment of seasonal influenza. We present the results for healthy adults (ie, adults without known comorbidities) and people at-risk of influenza-related complications. There was an overall reduction in the median time to symptom alleviation in healthy adults by 0.57 days (95% CI -1.07 to -0.08; p=0.02; 2701 individuals) with zanamivir, and 0.55 days (95% CI -0.96 to -0.14; p=0.008; 1410 individuals) with oseltamivir. In those at risk, the median time to symptom alleviation was reduced by 0.98 days (95% CI -1.84 to -0.11; p=0.03; 1252 individuals) with zanamivir, and 0.74 days (95% CI -1.51 to 0.02; p=0.06; 1472 individuals) with oseltamivir. Little information was available on the incidence of complications. In view of the advantages and disadvantages of different management strategies for controlling seasonal influenza in healthy adults recommending the use of antiviral drugs for the treatment of people presenting with symptoms is unlikely to be the most appropriate course of action.
    The Lancet Infectious Diseases 09/2009; 9(9):537-45. · 19.97 Impact Factor