Case-finding with the anxiety sub-scale of the Edinburgh Postnatal Depression Scale in an observational cohort:sensitivity, specificity, and cost-effectiveness

Background The Edinburgh Postnatal Depression Scale (EPDS) is effective and cost-effective for identifying postnatal depression. Postnatal anxiety is also common and can be identified by three questions on the EPDS (anxiety sub-scale). We aimed to compare EPDS score alone with EPDS score and sub-scale score together (EPDS+) to identify common mental illness (depression or anxiety) in postnatal women. Methods The sensitivity and specificity of the EPDS and sub-scale were explored. We developed a decision tree to compare costs and health outcomes associated with case-finding for postnatal depression or anxiety over one year. Model parameters were derived from secondary data analysis, published literature, and expert consultation. Costs included case-finding and treatment. Health benefit was measured as quality-adjusted life years (QALYs). We explored the cost-effectiveness of using EPDS alone and EPDS+ (versus no case-finding). Results The greatest number of true positive outcomes and smallest number of false negative outcomes were seen with EPDS+. However, the number of false positives is also higher for EPDS+. Compared with no case-finding, EPDS alone costs £3,365/QALY gained and EPDS+ costs £6,405/QALY gained. The additional health gain from EPDS+ (versus EPDS alone) costs £22,104/QALY. Limitations The model does not include long-term impacts of maternal mental illness or impacts on other family members. Conclusions Case-finding for common mental illness in the postnatal period is cost-effective. Compared to no case-finding, EPDS alone is more cost-effective than EPDS+. If decision-makers want to maximise identification of cases, EPDS+ could be cost-effective depending on how much they are willing to pay.