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 compared a low calorie diet (LCD) with a very low calorie diet (VLCD) for obese and severely obese patients who needed to lose weight prior to surgery that required a general anaesthetic. The LCD, which provided 800 kcal/day (53% carbohydrate, 24% protein and 23% lipids), consisted of a preparation (Optifast, Novartis Nutrition) that was combined with normal food. The VLCD comprised a preparation (Modifast, Novartis Nutrition) that provided 458 kcal/day (39.3% carbohydrate, 45.4% protein and 13.7% lipids), taken in three meals.

Treatment.

Cost-effectiveness analysis.

The study population comprised obese or severely obese patients (body mass index > 40 kg/m2) who had failed to lose weight following a conventional diet and who required surgery under general anaesthetic.

The setting was tertiary care. The economic was carried out in Alicante, Spain.

The dates to which the effectiveness and resource use data referred were not reported. No price year was reported.

The effectiveness data were derived from a single study.

The costing was carried out on the same patient sample that provided the clinical effectiveness data.

Sixty-seven patients were included in this study. Of these, 26 were in the VLCD group and 41 in the LCD group. The sample appears to have been a convenience sample, made up of those patients who presented at the institute during the study period and who met the inclusion criteria. No sample size or power calculations were reported.

From the information provided in this paper it would seem that the study was a non-randomised controlled trial. Patients presenting during the first 8 months of the study were allocated to the VLCD group, while those presenting in the last 8 months were allocated to the LCD group. The duration of follow-up was 4 weeks in the VLCD group and 12 weeks in the LCD group. The paper indicated that there was no loss to follow-up.

The analysis was undertaken on an intention to treat basis. The primary health outcomes were the mean weight loss, ponderal weight loss, glycaemia, systolic blood pressure, diastolic blood pressure, insulin resistance, total cholesterol and triglycerides, ureic acid, renal function and serum albumin. The two patient groups were shown to be comparable at baseline.

The mean weight loss was 9.28 kg in the VLCD group and 8.7 kg in the LCD group.

Ponderal weight loss was 7.2% in the VLCD group and 6.8% in the LCD group.

The reduction in total cholesterol in the VLCD group was greater than that in the LCD group (37.7 versus 8.1 mg/dL, p=0.002).

There were no statistically significant differences in changes in the other measurements between the two treatment groups.

Patients in the VCDL group experienced a higher number of minor adverse events than patients in the LCD group. They also experienced two major adverse events (cardiac arrhythmias and transitory ischaemic attack). There were no major adverse events in the LCD group.

The authors concluded that the LCD was safer than the VLCD.

No summary measure of health benefit was used in the economic analysis. In effect, a cost-consequences analysis was performed.

The direct costs to the hospital were included in the analysis. These covered health care personnel assistance, hospitalisations, medication costs, biochemical and hormonal analysis, electrocardiogram and emergency analysis. The resource use data were taken from the patient sample that provided the clinical effectiveness data, but the source of the unit costs was not reported. No price year was reported and discounting was not conducted.

The cost data was treated deterministically.

The indirect cost of sick leave was included in this study. The quantity of sick leave was taken from the clinical study that provided the effectiveness data, but the source of the unit cost was not stated. No price year was reported.

Euros (EUR).

No sensitivity analyses were undertaken.

See the 'Effectiveness Results' section.

The total costs were EUR 3,018.9 in the VLCD group compared with EUR 582.6 in the LCD group.

Not relevant.

The low calorie diet (LCD) was safer and more cost-effective than the very low calorie diet (VLCD).

This study compared an LCD and a VLCD for weight loss among obese and severely obese patients requiring surgery. No rationale for this choice of regimens was provided in the paper. You should consider how these options compare with usual practice in your own setting prior to applying the results of this study.

The measure of clinical effectiveness was taken from a prospective study. However, the paper did not contain sufficient detail to determine the internal validity of the study. The two patient groups were shown to be comparable at baseline, but the authors did not compare their patient sample with the wider patient population. As no sample size or power calculations were reported, it was unclear whether the study had sufficient power to identify statistically significant differences between the outcomes in the two treatment groups. The data analysis was performed on an intention to treat basis. Details of adverse events, in addition to the effectiveness results, were presented in full.

No summary measure of health benefit was used in the economic analysis. In effect, a cost-consequences analysis was performed.

The paper stated that the study was undertaken from a societal perspective, although it appears that direct non-medical costs have not been included in the analysis. It is not clear how this might have impacted on the study results. A breakdown of resource use and unit costs was provided and this will enhance the generalisability of the study. No statistical or sensitivity analyses were undertaken, which means that the uncertainty around the cost parameters has not been evaluated and the impact of this uncertainty on the results obtained has not been quantified. The price year was not reported, which will prevent any future reflation exercises.

The authors do not appear to have presented their results selectively and their conclusion reflected the scope of the analysis. They noted that their clinical findings were similar to other studies but did not compare their cost data with other published work. The authors did not consider whether their study findings could be generalised to other settings.

The authors did not make any recommendations for further research or changes in practice.

None stated.

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.