How much does it cost to retain antiretroviral therapy (ART) clients in care? Routine financial costs of retention interventions at Lighthouse Trust’s Martin Preuss Centre (MPC) in Lilongwe, Malawi

Introduction Antiretroviral therapy (ART) improves the health of people living with HIV (PLHIV). However, a high loss to follow-up, particularly in the first year after ART initiation, is problematic. The financial expenses related to client retention in low- and middle-income countries (LMICs) in sub-Saharan Africa are not well understood. This study aimed to comprehensively assess and quantify the financial costs associated with routine ART retention care at Lighthouse Trust’s (LT) Martin Preuss Centre (MPC), a large, public ART clinic in Lilongwe, Malawi. Methods We performed activity-based microcosting using routine data to assess the expenses related to routine ART retention services at the MPC for 12 months, January-December 2021. MPC provides an “ART Buddy” from ART initiation to 12 months. The MPC’s Back-to-Care (B2C) program traces clients who miss ART visits at any time. Clients may be traced and return to care multiple times per year. We assessed client retention costs for the first 12 months of treatment with ART and conducted a sensitivity analysis. Results The total annual cost of ART retention interventions at the MPC was $237,564. The proactive Buddy phase incurred $108,504; personnel costs contributed $97,764. In the reactive B2C phase, the total cost was $129,060, with personnel expenses remaining substantial at $73,778. The Buddy unit cost was $34 per client. The reactive B2C intervention was $17 per tracing event. On average, the unit cost for ART retention in the first year of ART averaged $22 per client. Conclusion This study sheds light on the financial dimensions of ART retention interventions at the MPC of LTs. ART retention is both costly and critical for helping clients adhere to visits and remain in care. Continued investment in the human resources needed for both proactive and reactive retention efforts is critical to engaging and retaining patients on lifetime ART.


Introduction
Antiretroviral therapy (ART) has demonstrated remarkable e cacy in mitigating HIV/AIDS-related morbidity and mortality, particularly in resource-limited settings [1,2].However, the full realization of its bene ts has been impeded by the high loss to follow-up (LTFU) [3], especially within the rst year of ART [4].Newly initiated ART clients are particularly vulnerable to treatment interruptions due to a multitude of factors, including the severity of their illness, di culties in disclosing their HIV status, and adaptation to life with HIV and ART [5,6].Estimates across sub-Saharan Africa (SSA) report an average of 65% retained in care at 36 months [3,7].Despite the critical importance of client retention, only a few studies have explored the costs of retaining clients in routine ART care in low-and middle-income countries (LMICs) in the SSA [8][9][10][11][12][13].
The Lighthouse Trust (LT), a national ART Center of Excellence in Lilongwe, Malawi, operates with the Malawi Ministry of Health (MoH) to provide HIV care, treatment, and support across Malawi [14].In its two urban agship clinics in Lilongwe, the LT serves more than 35,000 clients on ART: 24,000 at the Martin Preuss Centre (MPC) and 11,000 at Lighthouse (LH) [15].Clients at all LT clinics receive the same services, including integrated care, retention support, and clinical management, using an electronic medical records system (EMRS) [16].Since 2006, LH and MPC have implemented a client retention program, "Back-to-Care" (B2C), that traces ART clients who miss a clinic visit by ≥ 14 days by phone or a home visit.B2C plays a critical role in reaching and retaining LT clients in care [17][18][19].B2C is also reactive, waiting for clients to miss visits before intervention.In 2016, in response to growing concern about treatment interruption during the early stages of treatment, LT also introduced the Start Safely to ART (START) program in 2020.This initiative pairs all newly initiating ART clients with Expert Client Treatment Buddies.Buddies are HIV-positive peer mentors who provide vital psychosocial support and closely monitor up to 15 clients during the rst 12 months of critical ART initiation.
To ll gaps in understanding the overall cost of client retention in routine LMIC settings, the primary goal of this costing study is to conduct a comprehensive assessment and quanti cation of the nancial cost associated with routine ART retention services at the MPC during 2021.Understanding the nancial implications of proactive and reactive ART retention interventions at a large, public ART clinic in Lilongwe, Malawi, will contribute to the broader discourse regarding both retention and ART program sustainability.
The ndings may also help identify potential areas for cost optimization and improvements in resource allocation at the MPC and other public ART clinics in LMIC settings.

Objective
This comprehensive cost study aimed to improve the understanding of the nancial and economic implications of routine proactive and reactive retention interventions for ART clients at the MPC clinic in Lilongwe, Malawi.

Setting: Lighthouse Trust (LT) Martin Preuss Center (MPC)
MPC is the largest public provider of ART services in Malawi.LT umbrella policy and practice are the same across clinics, including all retention interventions.LT staff rotate between the MPC and LH locations as needed.All client data is managed in real time using the EMRS.ART clinic visits are scheduled monthly during the rst six months and then every three or six months if the patient is stable and adherent.B2C forms, including location information via phone and address details for tracing, are collected at initiation and ideally updated annually.As an indication of MPC patient volume, between April and June 2023, of 18,842 scheduled ART visits, 1798 (~ 10%) missed visits by ≥ 14 days and were referred to B2C.

Client retention programs
Proactive efforts before a visit or within 13 days of missed visits: The ART Buddy program ART patients receive more intense, proactive retention support from ART initiation through 12 months, alongside routine B2C.Following the initiation process, newly enrolled clients receive support from Expert Client "Buddies" during their initial 12 months of care.Expert clients have ~ 15 new ARTs available for support.These buddies remind clients of their scheduled ART visits and follow up with clients immediately after a missed visit, within 1-13 days of the appointment.Buddies also updates locator forms for clients who change contact information, such as phone numbers or home locations.If clients fail to report for any scheduled visit by 14 or more days, they are referred to B2C.Expert client budget services are only provided for clients during their rst year on ART, at which point clients continue in B2C only.
Reactive retention efforts after a missed visit ≥ 14 days: Back-to-care (B2C) B2C traces clients who missed visits by ≥ 14 days in accordance with MoH policy.[20] EMRS is used to identify and refer potential LTFU clients to tracing.A dedicated team of B2C tracers manually reviewed the LTFU list to identify and correct any errors in the EMRS data, removing people who attended visits from the tracing list.Clients with completed locator forms are initially traced by phone through SMS or calls, with up to ve attempts made, and if necessary, up to three home visits are attempted.In cases where clients are successfully reached, the B2C team of eld tracers and/or health promoters encourages those who have missed appointments or defaulted on treatment to return to care.The B2C team also conducts semiformal interviews with clients to assess the outcomes of their ART treatment and records this information on paper-based B2C forms, which data clerks subsequently input into the EMRS.The EMRS helps determine if and when a client returns to care, allowing for the cessation of B2C client followup for that speci c event or month.

Data collection
In adherence to the Global Health Cost Consortium Reference Case guidelines [21], we performed activitybased microcosting to assess the expenses related to routine ART retention activities at the MPC clinic in Lilongwe, Malawi.Our data encompassed both nancial and economic cost estimations for all resources and activities essential for executing the routine retention intervention.Cost information was obtained from the MPC expenditure records, payroll information, and procurement records.We used routine program data to estimate the number of ART clients retained and the number of tracing events in 2021.
The nancial costs accounted for the direct expenses incurred in the process of retaining ART clients, whereas the economic costs took into consideration the opportunity cost linked to overhead expenses.Since the perspective of the analysis was from the LT organizational perspective (payer), we excluded costs that were not incurred by the clinic, such as medication costs, which are paid by the government, and study-speci c personnel that would not be transferable to routine program implementation.

Data analysis
We categorized our cost data into two main groups: xed costs and recurrent costs (as shown in Table 1).
Fixed costs encompassed speci c activities such as the initial training of retention personnel, a one-time motorcycle insurance premium payment, text messaging system subscriptions, and the procurement of equipment and motorcycles.These xed expenses were incurred only at the outset of the intervention, when the equipment was expected to have a useful life of 5 years.In contrast, variable costs were essential for sustaining the intervention over time.These variable expenses were further subdivided into distinct input categories, including personnel costs, communication expenses for reaching and following up with ART clients, general o ce supplies, motorcycle maintenance for client tracing, fuel costs, protective gear for motorcycle riders, and overhead costs representing opportunity costs.
For equipment costs in 2021, we applied a discount rate of 3% over an assumed lifespan of 5 years.To calculate the unit cost of the proactive Buddy intervention, we divided the total expenses incurred during a two-week period by the number of new ARTs initiated in 2021.Conversely, the unit cost for the reactive B2C intervention was determined by dividing the total expenses incurred for ART retention beyond the initial two weeks by the number of tracing events.
All costs were converted from Malawi Kwacha (MWK) to US dollars using the 2021 exchange rate of 1$=825 MWK.Our analyses were conducted using Microsoft Excel (version 16.76; Microsoft, Redmond, WA).We also conducted a sensitivity analysis to assess how changes in personnel costs, a signi cant component of the intervention's expenses, might impact overall costs.This analysis was prompted by the inherent challenge of distinguishing personnel expenses related to ART intervention from those associated with routine care.

MPC ART clients
In 2021, there were 3,280 new ARTs initiated.Among these clients on ART, 7,588 had tracing events.All new ART clients are expected to have an initial encounter with a promoter to receive support during their rst year of treatment, ensuring their continued care.Additionally, the B2C approach encompasses tracing activities for individuals who missed appointments or defaulted on their treatment.

Retention costs
The total cost of ART retention interventions at the MPC is $237,564 (Table 2).The early retention buddy phase incurred a total cost of $108,504, with personnel costs being the most signi cant at $97,764, followed by training at $6,592.In the reactive retention B2C phase, the total cost was $129,060, with personnel expenses remaining substantial at $73,778.Overhead, fuel, and vehicle costs emerged as signi cant contributors, amounting to approximately $12,518, $10,427, and 9,105, respectively.

Per unit cost
The unit cost of ART retention care at the MPC for the Buddies, covering care for 3,280 new clients, was $34 (Table 4).In contrast, B2C, with 7,588 tracing events, yielded a lower unit cost of $17. Combining both Buddies and B2C, the overall unit cost for ART retention care at the MPC in 2021 averaged $22 per client/tracing event.

Cost drivers
Figures 1-2 provide an overview of the primary cost drivers for ART retention intervention in both the Buddy and B2C phases.In the proactive Buddy intervention (Fig. 1), personnel costs constitute the largest portion, accounting for 86% of the total expenses, while training and protective gear costs represent 6% and 3%, respectively.Moreover, during the reactive B2C intervention, personnel costs remained substantial but decreased to 57% (Fig. 2).Overhead and equipment costs become more prominent at 10% each, followed by fuel and protective gear costs, which make up 8% and 6%, respectively.

Sensitivity analysis
Considering the signi cant impact of personnel costs on both proactive Buddy and reactive B2C retention interventions, coupled with the ongoing trend of rising personnel expenses, the need for sensitivity analysis becomes paramount.We performed a univariate sensitivity analysis to evaluate the total and unit costs of the interventions.adjusting for a 25% increase in personnel costs, the proactive Buddy intervention increased from $108,000 to $136,000, a unit cost increase in Buddies from $33 to $42.Similarly, the cost of B2C intervention also increased from $129,000 to $147,000, resulting in a per-tracing cost increase from $17 to $19. The ndings indicate that proactive intervention is more personnelintensive and susceptible to changes in personnel costs than B2C intervention, as evidenced by the greater increase in cost per client retained.

Discussion
In this study, we provide a comprehensive breakdown of the routine costs associated with proactive and reactive ART retention interventions at the large, public ART clinic in Lilongwe, Malawi.This cost analysis provides valuable insights into the nancial aspects of an ART retention intervention conducted in a resource-constrained setting.In the proactive Buddy program, expenses totaled $108,504, with personnel costs being the largest contributor.The late retention programme, B2C, incurred a total cost of $129,060, where personnel expenses remained substantial but overhead, fuel, and vehicle expenses also played a signi cant role.The study highlights the critical cost drivers across retention phases, offering important information for LMIC policymakers and healthcare administrators to consider for retention service allocations and program planning.
Although this analysis was not speci cally a cost-effectiveness analysis, the unit cost analysis offers insights into the drivers of effective retention interventions.For the proactive retention programme, the unit cost per client (covering 3,280 new clients) was $34, while the late retention programme had a lower unit cost of $17 per tracing event (involving 7,588 tracing episodes).Although these numbers might suggest that proactive retention is more expensive and therefore less cost-e cient, this may be misleading.Early retention initiatives such as Buddies prevent or reduce the likelihood of missed visits, keep contact information updated, and may help foster engagement in care beyond the rst 12 months when Buddy supports sunset.Moreover, these ndings suggest that the $17 per tracing event is likely a reasonable cost to retain clients in care, suggesting continued investment in B2C.Overall, it appears that the combination of proactive and late program retention activities may be the most cost-e cient model, averaging $22 per client/tracing event.The average retention cost, $22, may serve as a valuable benchmark for evaluating cost e ciency and informing resource allocation decisions.
Retention efforts are recognized as critical but costly aspects of quality ART programs at scale.However, retention efforts at the MPC are lower, or far lower, than those reported previously, suggesting cost e ciency.For example, a recent costing study of three HIV retention models in SSA found that improving ART retention by 25% could cost between $93 and $6518/client [8].These retention costs pose sustainability challenges.MPC costs are more in line with lower-cost retention models, with retention efforts at $36.56 USD per client.According to a community-based tracing model in Tanzania, client tracing services had a unit cost of $47.56 USD, while support for the client returning to care was $206.77USD.For tracing services, B2C has a lower cost than this lower impact model [22].
Retention intervention costs at the MPC should not be used to overlook pervasive and persistent funding gaps that reduce Buddy or B2C effectiveness.Although retention at LT clinics, including the MPC, is consistently more than 75% at 12 months, retention at LT clinics still falls short: an average of 63% of ART clients are retained at 24 months.This is far below the 90% retention target needed for client VLSs and epidemic control.[22]Second, current resources provide resources only for clients during their rst 12 months of care, shortchanging clients who may bene t from longer-term support.Third, additional resources are needed to help update accurate location information.In 2021, 1,803 clients (29%) remained untraceable due to lack of actualized address information, preventing efforts to return clients to care.Furthermore, approximately 1,184 clients (19%) returned to the facility after the tracing list was generated and veri ed, leading to wasted tracing resources.Finally, gaps in B2C grow as client volume increases while funds decrease [23].At the MPC clinic from April to June 2023, only 40% (719/1798) of potential LTFU patients were successfully identi ed.Additional proactive retention efforts, such as LT's recent twoway texting system to improve early retention support [24,25], are needed to reduce LTFU before it happens.

Limitations
for complementary retention activities were not included; costs for activities such as Expert Client escorts from HIV testing sites were ignored; optional Buddy companionship during routine ART visits occurred in year 1; and additional adherence counseling with Expert Clients occurred, as they are outside the scope of routine retention in other LMIC settings.Other complementary Lighthouse programmes that enrich the client experience are outside the scope of retention-speci c activities but are likely to improve engagement in care.These initiatives include call center services designed to enhance client support and engagement, psychosocial counseling, and referral services for clients who have been exposed to GBV.This likely underestimates MPC retention costs.Moreover, the analytic approach has several limitations due to the use of routine data and funding limitations, including the focus on a single-center analysis, the assumption of linear sensitivity, the reliance on clinical records, and the absence of time-in-motion analysis to estimate the actual personnel cost.Finally, we did not cost the resources needed to return clients to care, an area for further expansion of this analysis in the future.Despite these limitations, this study provides valuable insights into the nancial aspects of ART retention interventions at the MPC, emphasizing the critical role of personnel expenses and the distribution of xed and variable costs across both the proactive and late program stages.

Conclusion
These ndings signi cantly contribute to our understanding of the nancial landscape surrounding ART retention interventions.To ensure the long-term sustainability and e ciency of the ART retention care program at the MPC, it is imperative to explore resource optimization strategies for both proactive and late retention programs while maintaining continuous cost monitoring and evaluation.To improve retention e ciency, focusing scarce retention resources on clients at the highest risk of LTFU and during time periods when the risk of LTFU is highest (e.g., ART initiation) may be advisable.Additionally, linkages between EMRSs between facilities, such as via a National Health Management Information System (HMIS), could reduce the impact of silent transfers (clients moving clinics informally) and those who receive emergency ART supplies while traveling.Overall, these results reinforce calls for healthcare policymakers and administrators to continue to advocate for retention resources to ensure the wellness of both PLHIV on ART and the overall ART program.

Figure 1 Cost
Figure 1

Table 2
Activity and input cost of ART retention care at the MPC in 2021 (USD)

Table 3
) costs were signi cantly greater at $98,587, accounting for 91% of the total cost.The overall cost of early intervention was $108,504.In contrast, B2C incurred higher xed (start-up) costs at $16,757, comprising 13% of the total cost, with variable (recurrent) costs of $112,303, making up 87% of the total cost.The total cost of B2C was $129,060.This breakdown offers valuable insights into the allocation of resources and the nancial aspects of ART retention care at the MPC.
provides a comprehensive breakdown of the xed and variable costs associated with ART retention care at the MPC, classi ed into proactive Buddy and reactive B2C interventions.For the Buddy activities, the xed (start-up) costs amounted to $9,647, representing 9% of the total cost, while the variable (recurrent

Table 4
Unit cost of ART retention care at the MPC in 2021 (USD)