Interventions:
The rationale for the selection of the comparators was clear and appropriate. Implanon was ranked as the most cost-effective LARC method in a recent NICE study and was compared with oral contraceptives.
Effectiveness/benefits:
The authors justified their selection of the study design, which was chosen to reflect everyday clinical practice. Thus, the data reflected the real-world pattern of care in the authors’ setting. The main drawback of this approach is that the retrospective use of an administrative database often does not provide the data appropriate to the objective of the study. Thus, some assumptions were required, which reduces the validity of the clinical findings. Despite matching the two samples, there were some differences in the clinical histories of the women. The benefit measure was the natural outcome of the contraceptive methods and was specific to these interventions. Therefore, it cannot be compared with the benefits of other health care strategies.
Costs:
The analysis of costs was consistent with the perspective of the Welsh NHS. The categories of costs were reported. Most of the economic data were derived from a previous analysis and the cost estimates were updated only for a few items. Thus, little information on the derivation of some cost estimates was provided. The price year was not reported and discounting would have been useful given the relatively long time frame of the analysis. The costs were treated deterministically and the impact of variations in individual items was not assessed.
Analysis and results:
The costs and benefits were not synthesised, but the more favourable clinical and economic outcomes showed the superior profile of the LARC. The issue of uncertainty was appropriately investigated using a probabilistic approach, but the methodology was not described. The authors stated that since the oral contraception group included both ongoing and new users, these might be more compliant and satisfied than a group of new users only. If this were the case, the results for the oral strategy would have been less cost-effective. The authors acknowledged some drawbacks of their study, mainly related to the source of clinical data.
Concluding remarks:
The study had some methodological limitations which might affect the validity of the authors’ conclusions.