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.

Fortification of grain with folic acid to prevent neural tube defects (spina bifida and anencephaly).

Primary prevention.

Cost-effectiveness analysis.

Women of child-bearing age (11 to 50 years).

Community. The economic study was carried out in California, USA.

Data on the effectiveness of folic acid fortification was taken from two studies published in 1989 and 1991. The data related to"domestic food disappearance" (a measure of human consumption representing the difference between total supply and other uses) were from 1991. The date of data related to other resources used were not systematically reported. The fiscal year was 1991.

Effectiveness data were based on a review of previously published studies and reports.

Effectiveness of folic acid assessed by the reduction in the risk of neural tube defects, proportion of target population with adequate folate intake at baseline, and effect of fortification on folate intake.

The authors claimed to have carried out a comprehensive review of the literature and reported on all known studies of relevance. Thus selection criteria were determined by relevance to the topic. The literature review included studies with different designs: three randomised controlled trials, four non-randomised controlled trials, six case-control studies and one cohort study.

Not reported.

Not stated.

Criteria to judge relevance were not explicitly stated by the authors. However, American studies were thought to be more relevant to the study population. A summary finding of the studies was reported.

The literature review included at least fourteen studies directly relevant to the outcomes assessed in the review.

Studies were combined using the narrative method.

Differences between the studies were discussed according to different criteria (such as studies having been conducted in high prevalence areas).

The authors chose to use a lower estimate of 50% for the effectiveness rate, provided by the Centers for Disease Control and Prevention. Literature based sensitivity limits of 67% and 20% were used. The proportion of target population with adequate folate intake at baseline was 33% (13% to 40%). The effect of fortification on folate intake was 17% (33% to 50%) with low-level fortification and 42% (33% to 75%) with high-level fortification .

The benefit measures were the percentage of patients shifted from high risk to low risk due to fortification, and cases of spina bifida and anencephaly averted for the population of 4,111,000 live births in the USA in 1991.

Costs were discounted. Quantities were not systematically reported separately from the costs. The cost components were reported separately. Total direct cost of fortification was the sum of food production costs (costs associated with the folate itself, labelling of products, assays to test folate levels and surveillance) and costs of adverse effects due to folic acid fortification (costs of cases of neurologic disease including the costs of hospitalisation, drugs, nursing home care, appliance and other professional services). The costs saved due to cases of spina bifida averted consisted of the costs of medical care, developmental services, special education, and human capital costs. Costs were calculated from a societal perspective. The quantity of folic acid required was calculated using assumptions of levels required as well as past data on grain consumption (1991). The sources of cost data were different national or local institutions. 1991 price data were used.

Costs were discounted. Quantities were not systematically reported separately from the costs. The indirect cost items were not reported. The indirect cost of adverse health effects due to folic acid fortification were considered. The source of the indirect cost estimation was a study published in 1985. 1991 price data were used.

US dollars ($).

One-way sensitivity analysis was performed on the discount rate, the baseline level of folate intake in the target population, the effectiveness of dietary folate in preventing neural tube defects, the threshold dose of folic acid that minimises the risk of an affected child and the cost of comprehensive surveillance.

The percentage of patients shifted from high risk to low risk due to low-level and high-level fortifications were 17% and 42%, respectively. Cases of spina bifida and anencephaly averted for the population of 4,111,000 live births in the USA in 1991 were 191, and 113 for low-level fortification; and 473, and 280 for high-level fortification, respectively.

The total direct costs of the intervention were estimated at $27.94million for low-level and $49.20 million for high-level fortification in 1991. The adverse effects caused by fortification (additional neurologic disease) were estimated to cost $16.4 million ($33,000 per case). The cost saved due to averted cases of spina bifida and anencephaly in 1991 were $121.5 million and $300.9 million with low-and high-level fortification, respectively. The net cost saving dueto low- and high-level fortification amounted to $93.6 million and $251.7 million, respectively. The discount rate was 4% (2.5% to 6%).

Costs and benefits were not required to be synthesized since the fortification strategies were dominant relative to both the alternative options. The direct cost per neural tube defect averted was estimated as a measure of synthesis of costs and benefit to compare the fortification strategies with the policy of promoting voluntary use of folate supplements. This measure amounted to $132,000 for the supplement use versus $92,000 and $65,000 for low-and high-level fortification, respectively.

By averting costly birth defects, folic acid fortification of grain in the US may yield substantial economic benefit.

The reason for the choice of the comparators is clear. The fortification strategies under investigation have been presented to the FDA's Folic Acid Subcommittee. You, as a database user, should consider whether these strategies are relevant in your own setting.

The authors provided insufficient details about the methods of identification of studies. Therefore, it is not clear whether the estimate of measure of benefit was based on a systematic review of the literature. Most of the studies are US-based and some of their findings might be specific to their country of origin.

Quantities were not systematically reported separately from the costs. However, adequate details of methods of cost estimation were given. Cost results might not be generalizable to other settings or countries.

The study was considered to be a cost-benefit analysis, but the measure of benefit in this study was "cases of spinabifida/anencephaly averted"; it should, therefore, be classified as a cost-effectiveness analysis.

Supported by the California Birth Defects Monitoring Program, a public health program funded by the California Department of HealthServices and administered by the March of Dimes Birth Defects Foundation.

Comments in: American Journal of Public Health 1995;85(11):1587-8, and American Journal of Public Health 1996;86(4):593-4.