This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn.

The study examined several smoking cessation interventions, including four nicotine replacement therapies (NRTs; gum, patch, inhaler and nasal spray) and three antidepressant medications (Zyban). Combinations of strategies were also considered. The full list of strategies was gum, patch, inhaler, nasal spray, Zyban, Zyban plus gum, Zyban plus patch, and gum plus patch. Zyban was given at a dose of 300 mg/day. Another two antidepressant drugs (clonidine 0.2 mg/day and nortriptyline 50 mg/day) were included in the analysis, but their cost-effectiveness was not fully assessed because they have significant side effects.

Primary prevention.

Cost-effectiveness analysis.

The study population comprised a hypothetical cohort of smokers.

The setting was primary care. The economic study was carried out in the USA.

The effectiveness and resource use data were derived from studies published in 1996 and 1999. The price year appears to have been 2004.

The clinical end point used in the model was treatment effectiveness. This was defined as the percentage of individuals not smoking at 6 months.

A simple decision model was constructed to evaluate the clinical and economic impact of the alternative smoking cessation interventions. The structure of the model was partially reported. The time horizon of the model was 6 months, but no other details of the model were given.

The clinical data were derived from the Surgeon General's Report, which analysed the cost-effectiveness of alternative smoking cessation strategies. It was unclear which sources were used in the Surgeon General's Report to estimate clinical data. Only data for the combination of Zyban and nicotine patch were derived from a published double-blinded randomised clinical trial. Data on the Zyban plus gum combination were not available, so its efficacy was based on author's assumptions.

The primary sources providing data on treatment success were identified selectively. No justification for their selection was reported.

The summary benefit measure was treatment success (percentage of individuals not smoking at 6 months). This was derived directly from the literature, as reported above.

The analysis of the costs was restricted to the costs to the Texas government. These included the costs of smoking cessation interventions, physician time and the pharmacy dispensing fee. The unit costs and the resource quantities were presented separately. Patterns of use of medications and other devices (duration and intensity) were derived from the Surgeon General's Report. The costs of pharmaceuticals came from the Drug Topics Red Book (average wholesale prices). A 15% Medicaid discount was applied. The cost of physician time was derived from the Texas Medicare reimbursement rate. Discounting was not relevant given the short time horizon of the analysis. The price year appears to have been 2004.

No statistical analyses of the costs were performed.

Productivity costs were not considered.

US dollars ($).

Sensitivity analyses were performed to assess the robustness of the cost-effectiveness ratios to variations in the clinical estimates and some costs. Alternative values were derived from the literature. In particular, a univariate sensitivity analysis investigated the effectiveness of the combined Zyban plus gum strategy (+/- 25% of the base-case estimate). A two-way sensitivity analysis tested the impact of simultaneous variations in effectiveness and prices.

The proportion of quitters at 6 months was:

0.237 with gum,

0.305 with Zyban,

0.330 with Zyban plus gum,

0.177 with patch,

0.286 with gum plus patch,

0.228 with inhaler,

0.330 with Zyban plus patch, and

0.305 with nasal spray.

The cost of each strategy was:

$77.5 with gum,

$230.6 with Zyban,

$292.2 with Zyban plus gum,

$226.6 with patch,

$398.3 with gum plus patch,

$468.7 with inhaler,

$551.4 with Zyban plus patch, and

$830.9 with nasal spray.

Incremental cost-effectiveness ratios were calculated to combine the costs and benefits of the alternative strategies.

After excluding dominated options (those with lower benefit and higher costs than at least one other strategy), the nicotine gum was the reference strategy. The incremental cost per successful patient was $2,251 with Zyban over gum and $2,466 with Zyban plus gum over Zyban alone.

The results of the sensitivity analysis did not alter the conclusions of the base-case analysis, as the relative ranking of the interventions did not change.

Nicotine gum appears to be the most cost-effective strategy for the general population. The value for money of Zyban was unclear due to the uncertain nature of the clinical data.

The rationale for the choice of the comparators was clear in that available strategies were selected for the analysis. The interventions were described and the reasons for excluding some were explained (e.g. clonidine and nortriptyline were excluded because they were not appropriate for widespread dissemination on account of their side effects). You should decide whether they are valid comparators in your own setting.

The effectiveness data were derived from studies that might have been identified selectively. Much of the clinical data came from a previous report, no details of which were provided. Thus, it was not possible to assess the validity of the clinical data given the information reported in the current study. Other data were derived from a clinical trial, which would usually have a high internal validity. Assumptions were made when no clinical data were available. Few sensitivity analyses were conducted, hence the clinical results should be treated with some caution.

The summary benefit measure was derived directly from the effectiveness analysis. It represents an intermediate measure that cannot be compared with the benefits of other health care interventions.

The analysis of the costs was consistent with the perspective adopted. Extensive information on the unit costs and resource quantities was provided, which will assist in replicating the analysis in other settings. The sources of the costs were reported for all items, and a clear description of the cost calculation was given. Discounting was considered. The impact of variations in prices and discounts was investigated in the sensitivity analysis. The price year was implicitly stated, which will enable the analysis to be replicated in other time periods. No statistical analysis of the costs was performed.

The author did not compare the findings with those from other studies, nor address the issue of the generalisability of the study results to other settings. Only limited sensitivity analyses were conducted, thus the external validity of the analysis was low. The author noted that the model was limited by the accuracy of the published data used. The costs and benefits of preventing smoking-related diseases were not considered and this appears to be an important limitation of the analysis, which was limited to the costs of smoking cessation interventions. The benefit measure used in the analysis meant that no firm conclusions on the cost-effectiveness of non-dominated strategies could be drawn.

The study results support the endorsement of nicotine gum as a cost-effective smoking cessation intervention.

No funding was received.

Because readers are likely to encounter and assess individual publications, NHS EED abstracts reflect the original publication as it is written, as a stand-alone paper. Where NHS EED abstractors are able to identify positively that a publication is significantly linked to or informed by other publications, these will be referenced in the text of the abstract and their bibliographic details recorded here for information.

Song F, Raftery J, Aveyard P, et al. Cost-effectiveness of pharmacological interventions for smoking cessation: a literature review and a decision analytic analysis. Med Dec Making 2002;22(5 Suppl):S26-37.

Croghan IT, Offord KP, Evans RW, et al. Cost-effectiveness of treating nicotine dependence: the Mayo Clinic experience. Mayo Clin Proc 1997;72:917-24.

Silagy C, Lancaster T, Stead L, et al. Nicotine replacement therapy for smoking cessation (Cochrane Review). In: The Cochrane Library, Issue 3, 2001. Oxford: Update Software.