Protocol for the economic evaluation of group interpersonal therapy for postnatal depression compared with high-quality standard care in Kenya and Lebanon (SUMMIT trial)

The SUMMIT trial

The SUMMIT trial is an individually randomised controlled superiority trial testing whether providing culturally adapted group-IPT to women with postnatal depression improves child cognitive development, maternal depression and the mother-child relationship. The recruitment of participants in the trial commenced on 2 January 2023 in Beirut, Lebanon and Nairobi, Kenya. It is anticipated the trial will end in June 2025. Participants were randomised to the intervention arm or the high-quality standard care (HQ-SC) control arm. All participants received HQ-SC, with participants in the intervention arm also receiving group-IPT. The trial will last for 52 weeks after screening and recruitment at baseline, with six points in time when study measures are collected over the duration of the trial, including baseline (T1), T2 at eight weeks, T3 at 13 weeks (end of group-IPT sessions), T4 at 24 weeks, T5 at 36 weeks and T6 at 52 weeks following baseline. The SUMMIT trial is described in detail elsewhere²³. Here, we outline the plan for the within-trial economic evaluation.

Objectives

We will carry out an economic evaluation of group-IPT compared with HQ-SC from a provider, patient and societal (sum of provider and patient) perspective to estimate the:

Patient and Public Involvement

Participants were involved in the piloting of economic evaluation measures during the feasibility phase of the study. Secondary outcome measures, the baseline questionnaire and the cross-sectional patient care-seeking and cost survey were tested during the feasibility trial. Participant feedback regarding acceptability and understanding helped inform measures subsequently included in the SUMMIT trial. The planned economic evaluation will not involve patients or the public in conceptualising other aspects of the study design or data analysis. However, relevant country stakeholders will be engaged during the dissemination of economic evaluation results.

Study setting and population

In Kenya, studies have generally found that between 13% and 19% of women experience postnatal depression, with some higher estimates^24,25. While many women do not seek care, most that do seek care go to public sector facilities. These range from level 1 community facilities, which primarily provide screening services and some basic treatment, up to level 6 National Referral Hospitals. SUMMIT study sites in Nairobi County include four level 3 facilities (Huruma Lions Health Centre, Riruta Health Centre, Githurai Health Centre, and Kangemi Health Centre), one level 5 (Mbagathi Hospital) and one level 6 facility (Mathari Teaching and Referral Hospital). Level 3 facilities in Kenya are prohibited from charging user fees²⁶ and are typically staffed with at least one doctor, clinical officers and nurses providing a comprehensive set of primary care services^26–28. Mbagathi and Mathari are large hospitals, both of which conduct research. Mbagathi is a secondary referral hospital while Mathari offers specialised mental health services.

Prevalence estimates for postnatal depression in Lebanon range between 12.8% and 21.8%^29,30, and a recent study has indicated that rates of postnatal depression are higher in Lebanon than in other countries³¹. The Beirut port explosion in 2020 and subsequent hyperinflation increased rates of mental health conditions generally³², while the conflict with Israel may have a further negative effect on mental health, and postnatal depression specifically. In Lebanon, all health facilities participating in the SUMMIT trial are primary health centres (PHCs), located in Beirut and affiliated with the Ministry of Public Health Network. These facilities include Makased Center PHC, Howard Karagheusian Commemorative Center, Dar Al Fatwa PHC, Dar El Hawraa PHC, and Hariri Foundation PHC.

In both countries, participants were screened using the Patient Health Questionnaire – depression module (PHQ-9)³³. Mothers aged 18 years or older, with an infant aged 6–35 weeks at the time of screening, were eligible to participate if they scored 12 or above on the PHQ-9 – defined as an indication of postnatal depression. Mothers with psychotic conditions including bipolar disorder, anorexia nervosa, or substance dependency, and mothers whose index infants had severe physical or neurodevelopmental problems, were excluded from the trial. All eligible mothers who consented to participate, were randomly allocated to the control or intervention arm, with 412 participants enrolled over a 10-month period in both countries (N=224 in the group-IPT arm, N=188 in the control arm). As mentioned previously, all participating mothers received HQ-SC, while mothers in the intervention arm also received group-IPT.

High-quality standard care (control) and group-IPT (intervention)

Standard care pathways for postnatal depression in Lebanon and Kenya differ between countries, with varying access and types of services provided. Overall, however, there is limited provision of care for postnatal depression in both settings and in some cases no services or activities are provided. In the SUMMIT trial, HQ-SC reflected standard care provision in each country with a guided psychoeducation intervention that consisted of two group sessions, each lasting 60–90 minutes, and a self-help book. The first group session focused both on psychoeducation and nutritional guidance. This was followed by an optional second session, during which mothers received an introduction to the WHO Doing What Matters in Times of Stress self-help workbook – on which the guided psychoeducation sessions were based.

Intervention arm participants received culturally adapted group-IPT in addition to HQ-SC, following the completion of HQ-SC sessions. Group-IPT aims to address interpersonal triggers of depression and consists of an initial individual session lasting up to 2 hours, followed by weekly group sessions and a concluding individual session lasting a further 2–3 hours. Sessions are in-person and involve one or more facilitators talking with and supporting participants to identify links between depression and problems in life, encouraging group learning while developing the communication and interpersonal skills required to manage problems more effectively. In addition to initial and concluding sessions, group-IPT in the SUMMIT trial included eight weekly group sessions as per the WHO group-IPT manual¹⁵. Sessions took place in a room within the health facilities participating in the trial. Each group comprised 6–10 participants and lasted 90 minutes. Group-IPT sessions in Lebanon were facilitated by a licensed psychologist, while sessions in Kenya were facilitated by two community health workers per group. Group-IPT was adapted for cultural relevance and appropriateness in each country as part of the SUMMIT trial and more detail is provided on both group-IPT and HQ-SC in the main trial protocol paper²³.

Outcome measurement

The primary outcome of the SUMMIT trial is the cognitive development of the index child, as measured by the Malawi Developmental Assessment Tool (MDAT)³⁴. The MDAT will be administered at the trial endline, at 52-weeks (T6) following baseline measurement. Secondary trial outcomes include levels of depression among participating mothers, measured using the PHQ-9³³, and two measures to assess the general health and well-being of participating mothers, the EuroQoL-5 Dimensions (EQ-5D-5L) questionnaire and the ICEpop CAPability measure for Adults (ICECAP-A)^35,36. The PHQ-9 is administered at every timepoint, while the EQ-5D-5L and ICECAP-A are administered at four points in time during the trial, at baseline and then at 13, 24 and 52 weeks respectively. Measures at baseline and at the end of group-IPT intervention delivery, 13 weeks after baseline, will enable us to estimate the immediate effect of group-IPT on depression, general health and wellbeing compared with the HQ-SC control. Follow-up measures after the end of group-IPT intervention delivery, at 24 weeks and 52 weeks following baseline, will enable us to assess whether any effects of group-IPT on secondary outcomes persist or ‘fade out’ over time. Where required, permission was obtained to use measures prior to their inclusion in the SUMMIT trial.

Identification, measurement and valuation of resource use

Activity-based micro-costing will be carried out and supplemented with a top-down approach where required due to available data (e.g. facility overheads). A time horizon of 52 weeks (12 months) will be adopted. This is in line with the main trial duration for outcome measurement, where the final timepoint is 52 weeks after participant recruitment at baseline. Direct and indirect cost data are being collected from providers and patients, in line with the societal perspective of the study. Cost categories and data sources are summarised in Table 1.

Provider costs are being incurred by local trial partners and the facilities developing and implementing group-IPT within the trial. Financial costs from trial partner project accounts will be entered into a costing tool in Microsoft Excel. The tool will capture cost structures during start-up and implementation of HQ-SC and group-IPT and estimate costs of different intervention components such as manual adaptation, group facilitation and supervision. Interviews with project staff and monthly staff timesheets will inform the allocation of costs across intervention components. Economic costs will be estimated by assigning current market value to any donated or volunteer time reported in project records or interviews with project and facility staff.

Facility capital and overhead costs will be informed by data collected during facility visits, from observations, facility records, and staff interviews. Data collected from facilities will be inputted into an Excel-based cost-capture tool which separately captures surface area use, utilities and other costs. All study facilities have been visited in Lebanon except for Dar El Hawraa PHC, as it is similar in size and function to other included PHC facilities. In Kenya, Mathari Teaching Referral Hospital and Huruma Lions Health Centre were not visited as they are, respectively, largely comparable to Mbagathi Hospital and other included level 3 facilities.

To capture costs from the patient perspective, a cross-sectional survey was administered to study participants at the end of group-IPT intervention delivery, 13 weeks after baseline. The survey asks about costs related to sessions that participants attended and about any health problems or care-seeking in the preceding month. This includes questions to capture the direct and indirect costs of attending sessions, such as travel costs or lost income, as well as any direct or indirect costs of subsequent referrals or care-seeking.

Currencies and years of cost data are being recorded and will be adjusted for inflation to a base year of analysis (2023) separately for each country. The number of sessions attended per participant is being captured through trial participant case report forms and will be used to estimate annual costs per participant. Each session recorded in participant case report form attendance data will be costed based on the type of session (HQ-SC session or a group-IPT initial, group or concluding session) and the facility where the session took place. Costs will be captured and presented separately by trial arm, and for Kenya and Lebanon. To improve comparability between countries, costs will be presented both in local currencies (Kenyan Shillings and Lebanese Liras) and international dollars (Int$) adjusted for purchasing power parity.

Economic evaluation

In line with the main trial analysis²³, the cost-effectiveness analysis will be carried out on an intention-to-treat (ITT) basis. We will adhere to the Consolidated Health Economic Evaluation Reporting Standards (2022) and draw on best-practice guidance outlined in relevant economic evaluation reference cases^37,38. Start-up and implementation costs will be included in the main analysis, which will report financial and economic costs of group-IPT, along with incremental cost-effectiveness ratios (ICERs) compared with HQ-SC. An ICER will be calculated for the trial primary outcome, which is child cognitive development measured by the MDAT at endline (T6, 52-week follow-up). The ICER will be equal to the arithmetic mean difference in cost between group-IPT and HQ-SC divided by the arithmetic mean difference in effect (MDAT score). Given the 52-week time horizon of analysis, costs and outcomes will not require conversion to present value using a discount rate.

We will also calculate ICERs for secondary trial outcomes on which the trial is shown to have a significant effect. If the trial is found to have a significant effect on depression levels of participating mothers, an ICER will be calculated based on the PHQ-9. To facilitate comparison with other economic evaluations of health interventions, we will report an ICER for the incremental cost per quality-adjusted life year (QALY) gained. QALYs will be calculated based on participant responses to the EQ-5D-5L self-reported questionnaire. Given that group-IPT has the potential to impact more than just health-related quality of life, we will also report the incremental cost per year of full capability (YFC) based on participant responses to the ICECAP-A, which uses Sen’s capability approach to measure general wellbeing³⁹. This may not only better capture intervention effects but also enable comparison against other public policy interventions outside health⁴⁰.

Two-way sensitivity analyses will investigate the impact on ICERs of varying key cost drivers (e.g. staff) as well as uncertainty around effectiveness. Sensitivity analyses will also test for variations in ICERs of statistically significant adult outcomes at different timepoints, mainly at the end of group-IPT intervention delivery 13 weeks after baseline (T3) and follow-ups at 24 weeks (T4) and 52 weeks (T6) after baseline. To inform policymakers on the likely cost-effectiveness of group-IPT relative to HQ-SC, estimated ICERs, namely incremental costs per QALY gained, will be evaluated against country cost-effectiveness thresholds for Kenya and Lebanon⁴¹.

Interventions can be cost-effective, but this does not guarantee they are affordable or feasible in a given context. Information on the total cost required to scale up an intervention is needed for policymakers deciding how best to allocate resources. We will therefore estimate the total implementation costs to providers of scaling up group-IPT provision nationally. Total costs will be estimated separately for Kenya and Lebanon, based on national prevalence estimates of postnatal depression. The total cost to providers will also be expressed as a percentage of national health spending and gross domestic product to enable policymakers in each country to assess whether group-IPT is affordable in their context.

Equity impact

To assess whether some population groups benefit disproportionately from group-IPT, we will investigate how group-IPT outcomes are distributed across socioeconomic groups. This will be done by analysing the marginal mean difference in outcomes between trial arms within socioeconomic groups. Socioeconomic quintiles will be constructed based on household income, assets, participant and household characteristics. Quintiles will be generated using data collected through a questionnaire administered to participating mothers at baseline.

In addition to the distribution of group-IPT outcomes across quintiles, we will estimate whether participants experienced financial hardship due to costs they incurred. Catastrophic health expenditure is a commonly used measure of financial hardship, defined as when patient costs exceed a specified proportion of their income or capacity to pay (non-essential spending or consumption)^42,43. Costs incurred by SUMMIT participants, which will be captured through the cross-sectional patient care-seeking and cost survey mentioned above, will be defined as catastrophic if they exceed the commonly used cut-off of 10% of their income⁴⁴.

Study status

The SUMMIT trial is ongoing and planned to finish in June 2025. Group-IPT sessions and high-quality standard care provision have been completed, and data collection is ongoing for the trial endline. Following this the data will be locked and analyses will begin.