What Does "Success” Mean in the Cost-Effectiveness of Fetal Fibronectin Testing? [Response to Letter]

Résumé fourni par la source

We thank Dr. Sarıoğlu for his careful and constructive appraisal of our study and for recognizing the importance of generating real-world, Qatar-specific evidence on the clinical and economic implications of fetal fibronectin (fFN) testing.We appreciate the opportunity to clarify the three issues raised regarding the definition and interpretation of the effectiveness endpoint, the relationship between the decision-analytic model and observed clinical practice, and the costing calculations presented in Table 2.These points are addressed individually below. 1 Definition and Interpretation of the Effectiveness EndpointWe thank Dr. Sarıoğlu for emphasizing the importance of clearly defining and specifying the direction of the effectiveness endpoint.In our economic model, the effectiveness event was defined as delivery occurring within 48 hours of admission.This definition was applied consistently throughout the underlying analysis and served as the basis for the decision-analytic model.The model included six patient pathways across two comparator arms: fFN testing and no-fFN testing.Within the fFN arm, pathways were further categorized by whether the fFN result was positive or negative, and whether delivery took place within 48 hours.Similarly, Table 3 reported delivery within 48 hours as the primary clinical endpoint.This occurred in 94% of women in the fFN group and 80% in the no-fFN group, whereas delivery beyond 48 hours was reported as a secondary outcome.The probabilities and costs incorporated in the economic model were derived using this endpoint definition.We acknowledge, however, that the wording used to describe this outcome was not consistent across the manuscript.Specifically, the terms "successful delivery within 48 hours" and "successful prolongation of delivery within 48 hours" were used in the Methods, while the Discussion referred to "successful prolongation of pregnancy beyond 48 hours."We agree that these phrases are not equivalent and could create confusion about the intended direction of the endpoint.To clarify, the endpoint analyzed in the study was delivery within 48 hours, rather than prolongation of pregnancy beyond 48 hours.The references to "prolongation" in the narrative did not reflect a different definition or coding of the endpoint used in the analysis.We appreciate the opportunity to clarify this distinction and the intended interpretation of the reported outcome.We also agree that delivery within 48 hours should not be interpreted as a therapeutic effect attributable to fFN testing itself.fFN is a diagnostic and risk-stratification tool, not an intervention designed to accelerate or delay delivery.Its main clinical value is to inform the short-term risk of preterm delivery and to guide subsequent management decisions.In particular, the high negative predictive value of fFN may help identify women at low risk of imminent delivery, potentially reducing unnecessary interventions such as hospitalization, transfer, corticosteroid use, or tocolytic treatment.

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