Cost and Impact of Dried Blood Spot Versus Plasma Separation Card for Scale-up of Viral Load Testing in Resource-limited Settings

Clinical evaluation of patterned dried plasma spot cards to support quantification of HIV viral load and reflexive genotyping

Quantifying viral load, a key indicator required to achieve control and elimination of the HIV epidemic, requires cell-free plasma or serum to ensure measurements are not biased by proviral DNA contained in infected CD4 T lymphocytes. Plasma separation cards (PSC) collect and preserve a dried specimen, which makes them practical solutions for decentralized sample collection and transport in limited-resource settings. However, physiological variations in hematocrit levels can introduce significant variability in the quality of plasma generated by commercial PSCs and can lead to inaccurate test results and clinical decisions. In addition to hematocrit-dependent sampling, the Roche PSC, a standard for dried plasma collection, is known to induce considerable hemolysis, which further impacts specimen quality, concordance with liquid plasma, and the overall benefit of microsampling. We address these gaps with a patterned dried plasma spot (pDPS) card, which generates plasma with improved hematocrit independence and minimal hemolysis. This study directly compares pDPS cards to the Roche PSC to measure HIV viral load. Analysis of viral load from 75 donors revealed strong agreement in sensitivity, specificity, overall accuracy, and viral load band placement between devices, with quantitative metrics suggesting improved performance for pDPS cards. In reflexive genotyping, remnant dried blood from pDPS cards exhibited greater success than Roche PSC in amplification and sequencing (71% vs. 62%) and detecting drug resistance mutations (63% vs. 42%). Based on this performance, pDPS cards can be versatile across multiple analytical platforms, integrate seamlessly into existing clinical laboratory workflows, and aid clinicians in making accurate treatment decisions.

Clinical diagnosis of viral hepatitis: Current status and future strategies

Viral hepatitis (VH) is a significant public health issue with tremendous potential to aggravate into chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. Recent decade has witnessed remarkable uprising in the drug development and effective treatment of VH. An upsurge is seen in identification of antiviral therapies with low rates of viral resistance, the improvement of Hepatitis B Virus (HBV) vaccination and the development of direct-acting antivirals for Hepatitis C Virus (HCV). But unfortunately, the "2030 worldwide eradication" objective of World Health Organization (WHO) is still unmet. It can be largely attributed to the deficit faced by the healthcare system concerning screening and diagnosis. A timely, accurate and comprehensive screening; encompassing maximum population coverage is essential to combat this disease. However, advancements in VH diagnostics remain inadequate and with a marginal use in routine practice. This paper deliberates upon the lacunae in traditional and prevailing diagnostic methodology of viral hepatitis, especially their inadequacy in meeting the unique situations prevailing low- and middle-income countries (LMIC).

Performance of two plasma separation devices for HIV-1 viral load measurement in primary healthcare settings

IMPORTANCE

Burnett and HemaSpot are two novel technologies that allow whole blood collection and plasma separation and stabilization at room temperature without the need of additional equipment. Hence, these devices are potential alternatives to fresh plasma as a suitable specimen for viral load scale-up to monitor antiretroviral therapy in resource-limited settings.

Verification of dried blood spot as a sample type for HIV viral load and early infant diagnosis on Hologic Panther in Zambia

OBJECTIVE

Zambia has embarked on improving the diagnostic capacity by setting up high throughput and accurate machines in the testing process and introduction of dried blood spot (DBS) as a sample type. This was a cross sectional study to verify dried blood spot as a sample type for HIV viral load and early infant diagnosis (EID) on Hologic Panther platform and Evaluate the analytical performance (precision, linearity and measurement of uncertainty) of the Hologic Panther.

RESULTS

The specificity and sensitivity of EID performance of Aptima Quant Dx assay on Hologic panther machine against the gold standard machine COBAS Taqman (CAP/CTM) was 100% with an overall agreement of 100%. The quantitative HIV Viral Load (VL) accuracy had a positive correlation of (0.96) obtained against the gold standard (plasma samples) run on COBAS4800 platform. Analytical performance of the Hologic panther machine was evaluated; Precision low positive repeatability 3.50154 and within lab 2.268915 at mean 2.88 concentration and precision high positive repeatability 1.116955 and within lab 2.010677 at mean 5.09 concentration were obtained confirming manufacturers claims. Uncertainty of measurement for this study was found to be ± 71 copies/ml. Linearity studies were determined and all points were within acceptable limits. We therefore recommend DBS as a sample type alternative to plasma for the estimation of HIV-1 viral load and EID diagnosis on the Hologic panther machine.

Microsampling tools for collecting, processing, and storing blood at the point-of-care

In the wake of the COVID-19 global pandemic, self-administered microsampling tools have reemerged as an effective means to maintain routine healthcare assessments without inundating hospitals or clinics. Finger-stick collection of blood is easily performed at home, in the workplace, or at the point-of-care, obviating the need for a trained phlebotomist. While the initial collection of blood is facile, the diagnostic or clinical utility of the sample is dependent on how the sample is processed and stored prior to transport to an analytical laboratory. The past decade has seen incredible innovation for the development of new materials and technologies to collect low-volume samples of blood with excellent precision that operate independently of the hematocrit effect. The final application of that blood (i.e., the test to be performed) ultimately dictates the collection and storage approach as certain materials or chemical reagents can render a sample diagnostically useless. Consequently, there is not a single microsampling tool that is capable of addressing every clinical need at this time. In this review, we highlight technologies designed for patient-centric microsampling blood at the point-of-care and discuss their utility for quantitative sampling as a function of collection material and technique. In addition to surveying methods for collecting and storing whole blood, we emphasize the need for direct separation of the cellular and liquid components of blood to produce cell-free plasma to expand clinical utility. Integrating advanced functionality while maintaining simple user operation presents a viable means of revolutionizing self-administered microsampling, establishing new avenues for innovation in materials science, and expanding access to healthcare.

Identification of host biomarkers from dried blood spots for monitoring treatment response in extrapulmonary tuberculosis

There is a lack of objective tools for monitoring treatment response in extrapulmonary tuberculosis (EPTB). This study aimed to explore the utility of inflammatory biomarkers from the dry blood spots (DBS) as a tool for monitoring treatment response in EPTB. In a prospective cohort study, 40 inflammatory biomarkers were investigated in DBS samples from 105 EPTB cases using a Luminex platform. The samples were taken before, and, at the end of the 2nd and 6th months of treatment. A total of 11 inflammatory host biomarkers changed significantly with treatment in all EPTB patients. CXCL9/MIG, CCL20, CCL23, CXCL10/IP-10, CXCL1, CXCL2, and CXCL8 significantly declined in our cohort of EPTB (48 TB pleuritis and 57 TB lymphadenitis) patients at both time points. A biosignature consisting of MIG, CCL23, and CXCL2, corresponded with the treatment response in 81% of patients in the 2nd month and 79% of patients at the end of treatment. MIG, CCL23, IP-10, and CXCL2 changed significantly with treatment in all patients including those showing partial clinical response at the 2nd month of treatment. The changes in the levels of inflammatory biomarkers in the DBS correspond with the treatment success and can be developed as a routine test in low-resource settings.

Interventions to enhance testing and linkage to treatment for hepatitis C infection for people who inject drugs: A systematic review and meta-analysis

BACKGROUND

With the advent of direct acting antiviral (DAA) therapies for the treatment of hepatitis C virus (HCV), the World Health Organization recommended a goal to eliminate HCV as a public health threat globally by 2030. With the majority of new and existing infections in high income countries occurring among people who inject drugs, achieving this goal will require the design and implementation of interventions which address the unique barriers to HCV care faced by this population.

METHODS

In this systematic review and meta-analysis, we searched bibliographic databases and conference abstracts to July 21, 2020 for studies assessing interventions to improve the following study outcomes: HCV antibody testing, HCV RNA testing, linkage to care, and treatment initiation. We included both randomised and non-randomised studies which included a comparator arm. We excluded studies which enrolled only paediatric populations (<18 years old) and studies where the intervention was conducted in a different healthcare setting than the control or comparator. This analysis was restricted to studies conducted among people who inject drugs. Data were extracted from the identified records and meta-analysis was used to pool the effect of interventions on study outcomes. This study was registered in PROSPERO (CRD42020178035).

FINDINGS

Of 15,342 unique records, 45 studies described the implementation of an intervention to improve HCV testing, linkage to care and treatment initiation among people who inject drugs. These included 27 randomised trials and 18 non-randomised studies with the risk of bias rated as "critical" for most non-randomised studies. Patient education and patient navigation to address patient-level barriers to HCV care were shown to improve antibody testing uptake and linkage to HCV care respectively although patient education did not improve antibody testing when restricted to randomised studies. Provider care coordination to address provider level barriers to HCV care was effective at improving antibody testing uptake. Three different interventions to address systems-level barriers to HCV care were effective across different stages of HCV care: point-of-care antibody testing (linkage to care); dried blood-spot testing (antibody testing uptake); and integrated care (linkage to care and treatment initiation).

INTERPRETATION

Multiple interventions are available that can address the barriers to HCV care for people who inject drugs at the patient-, provider-, and systems-level. The design of models of care to improve HCV testing and treatment among people who inject drugs must consider the unique barriers to care that this population faces. Further research, including high-quality randomised controlled trials, are needed to robustly assess the impact these interventions can have in varied populations and settings.

Optimising courier specimen collection time improves patient access to HIV viral load testing in South Africa

BACKGROUND

South Africa uses a courier network for transporting specimens to public laboratories. After the daily collection of specimens from the facility by the courier, patients not yet attended to are unlikely to receive same-day blood draws, potentially inhibiting access to viral load (VL) testing for HIV patients.

OBJECTIVE

We aimed to design an optimised courier network and assess whether this improves VL testing access.

METHODS

We optimised the specimen transport network in South Africa for 4046 facilities (November 2019). For facilities with current specimen transport times (n = 356), we assessed the relationship between specimen transport time and VL testing access (number of annual VL tests per antiretroviral treatment patient) using regression analysis. We compared our optimised transport times with courier collection times to determine the change in access to same-day blood draws.

RESULTS

The number of annual VL tests per antiretroviral treatment patient (1.14, standard deviation: 0.02) was higher at facilities that had courier collection after 13:36 (the average latest collection time) than those that had their last collection before 13:36 (1.06, standard deviation: 0.03), even when adjusted for facility size. Through network optimisation, the average time for specimen transport was delayed to 14:35, resulting in a 6% - 13% increase in patient access to blood draws.

CONCLUSION

Viral load testing access depends on the time of courier collection at healthcare facilities. Simple solutions are frequently overlooked in the quest to improve healthcare. We demonstrate how simply changing specimen transportation timing could markedly improve access to VL testing.

Direct Processing and Storage of Cell-Free Plasma Using Dried Plasma Spot Cards

Plasma separation cards represent a viable approach for expanding testing capabilities away from clinical settings by generating cell-free plasma with minimal user intervention. These devices typically comprise a basic structure of the plasma separation membrane, unconstrained porous collection pad, and utilize either (i) lateral or (ii) vertical fluidic pathways for separating plasma. Unfortunately, these configurations are highly susceptible to (i) inconsistent sampling volume due to differences in the patient hematocrit or (ii) severe contamination due to leakage of red blood cells or release of hemoglobin (i.e., hemolysis). Herein, we combine the enhanced sampling of our previously reported patterned dried blood spot cards with an assembly of porous separation materials to produce a patterned dried plasma spot card for direct processing and storage of cell-free plasma. Linking both vertical separation and lateral distribution of plasma yields discrete plasma collection zones that are spatially protected from potential contamination due to hemolysis and an inlet zone enriched with blood cells for additional testing. We evaluate the versatility of this card by quantitation of three classes of analytes and techniques including (i) the soluble transferrin receptor by enzyme-linked immunosorbent assay, (ii) potassium by inductively coupled plasma atomic emission spectroscopy, and (iii) 18S rRNA by reverse transcriptase quantitative polymerase chain reaction. We achieve quantitative recovery of each class of analyte with no statistically significant difference between dried and liquid reference samples. We anticipate that this sampling approach can be applied broadly to improve access to critical blood testing in resource-limited settings or at the point-of-care.

903 Protein Saver cards: the best alternative for dried blood spot storage at room temperature for HCV RNA

Hepatitis C virus (HCV) infection remains a global health problem, detected only in the early stages by molecular tests. Molecular tests detect HCV RNA, which is very prone to degradation by ribonucleases, reason why blood samples must be transported and stored at − 20 °C, or even − 70 °C for long-term storage. Flinders Technology Associates (FTA) cards are a useful sampling collecting device for dry blood spot (DBS) storage, especially for low and middle-income countries (LMIC). In this study, we analyzed viral HCV RNA integrity for long-term storage at room temperature compared to − 20 °C using two different types of cards for DBS: FTA Classic and 903 Protein Saver cards. For this purpose, DBS were prepared on these cards using blood or plasma samples from HCV infected patients, and samples were analysed by conventional RT-PCR. Our results showed that 903 Protein Saver cards are the best and cheapest alternative for DBS storage at room temperature. In these conditions, we found that HCV RNA integrity lasted for up to 9 months.

The early-stage comprehensive costs of routine PrEP implementation and scale-up in Zambia

Pre-exposure prophylaxis (PrEP) is an effective HIV prevention option, but cost-effectiveness is sensitive to implementation and program costs. Studies indicate that, in addition to direct delivery cost, PrEP provision requires substantial demand creation and client support to encourage PrEP initiation and persistence. We estimated the cost of providing PrEP in Zambia through different PrEP delivery models. Taking a guidelines-based approach for visits, labs and drugs, we estimated the annual cost of providing PrEP per client for five delivery models: one focused on key populations (men-who-have-sex-with-men (MSM) and female sex workers (FSW), one on adolescent girls and young women (AGYW), and three integrated programs (operated within HIV counselling and testing services at primary healthcare centres). Program start-up and support costs were based on program expenditure data and number of PrEP sites and clients in 2018. PrEP clinic visit costs were based on micro-costing at two PrEP delivery sites (2018 USD). Costs are presented in 2018 prices and inflated to 2021 prices. The annual cost/PrEP client varied by service delivery model, from $394 (AGYW) to $655 (integrated model). Cost differences were driven largely by client volume, which impacted the relative costs of program support and technical assistance assigned to each PrEP client. Direct service delivery costs ranged narrowly from $205-212/PrEP-client and were a key component in the cost of PrEP, representing 35-65% of total costs. The results show that, even when integrated into full service delivery models, accessing vulnerable, marginalised populations at substantial risk of HIV infection is likely to cost more than previously estimated due to the programmatic costs involved in community sensitization and client support. Improved data on individual client resource usage and outcomes is required to get a better understanding of the true resource utilization, expected outcomes and annual costs of different PrEP service delivery programs in Zambia.

Eliminating HIV transmission through breast milk from women taking antiretroviral drugs

Ameena Goga and colleagues argue that frequent testing of maternal viral load is needed to eliminate HIV transmission through breast milk in low and middle income settings

Community-based delivery of HIV treatment in Zambia: costs and outcomes

OBJECTIVE

The aim is to determine the total annual cost per patient treated and total cost per patient retained on antiretroviral therapy in Zambia in conventional care in facilities and across community-based differentiated service delivery (DSD) models.

DESIGN

Economic evaluation was conducted using retrospective electronic record review.Twenty healthcare facilities (13 with DSD models and 7 as comparison sites) in six of Zambia's 10 provinces were considered.

METHODS

All individuals on antiretroviral therapy (ART) >18 years old at the study sites were enrolled in a DSD model or conventional care by site type, respectively, with at least 12 months of follow-up data. Accessing care through DSD models [community adherence groups (CAGs), urban adherence groups (UAGs), home ART delivery and care, and mobile ART services] or facility-based conventional care with 3-monthly visits. Total annual cost per patient treated and the annual cost per patient retained in care 12 months after model enrolment. Retention in care was defined as attending a clinic visit at 12 months ± 3 months.

RESULTS

The DSD models assessed cost more per patient/year than conventional care. Costs ranged from an annual $116 to $199 for the DSD models, compared with $100 for conventional care. CAGs and UAGs increased retention by 2 and 14%, respectively. All DSD models cost more per patient retained at 12 months than conventional care. The CAG had the lowest cost/patient retained for DSD models ($140-157).

CONCLUSIONS

Although they achieve equal or improved retention in care, out-of-facility models of ART were more expensive than conventional care.

Bringing Data Analytics to the Design of Optimized Diagnostic Networks in Low- and Middle-Income Countries: Process, Terms and Definitions

Diagnostics services are an essential component of healthcare systems, advancing universal health coverage and ensuring global health security, but are often unavailable or under-resourced in low- and middle-income (LMIC) countries. Typically, diagnostics are delivered at various tiers of the laboratory network based on population needs, and resource and infrastructure constraints. A diagnostic network additionally incorporates screening and includes point-of-care testing that may occur outside of a laboratory in the community and clinic settings; it also emphasizes the importance of supportive network elements, including specimen referral systems, as being critical for the functioning of the diagnostic network. To date, design and planning of diagnostic networks in LMICs has largely been driven by infectious diseases such as TB and HIV, relying on manual methods and expert consensus, with a limited application of data analytics. Recently, there have been efforts to improve diagnostic network planning, including diagnostic network optimization (DNO). The DNO process involves the collection, mapping, and spatial analysis of baseline data; selection and development of scenarios to model and optimize; and lastly, implementing changes and measuring impact. This review outlines the goals of DNO and steps in the process, and provides clarity on commonly used terms.

Dried blood spot cards: A reliable sampling method to detect human antibodies against rabies virus

Background

Although preventable by vaccination for more than a century, rabies virus still causes numerous fatalities every year. To determine antibody levels in humans, blood collected with a finger prick and applied on dried blood spot (DBS) cards is an alternative for venipuncture. The use of DBS is specifically valuable in remote areas, as it is easy to perform, store and transport. Therefore, the technique is frequently used for epidemiological studies of tropical diseases. Up to present, determination of rabies virus antibody levels on human DBS has not been validated.

Methodology/Principal findings

We evaluated the use of human DBS for rabies serology and analyzed 99 pre- or post-vaccination serum and DBS samples with a fluorescent antibody virus neutralization test (FAVNt), which is the gold standard to detect protective antibody levels, and a Bio-Rad Platelia Rabies II ELISA. Sensitivity and specificity of DBS eluates tested with the FAVNt were 97% and 92%, respectively and 87% and 96% when tested with the Platelia-II ELISA. Antibody levels measured in serum with the FAVNt, correlated best with antibody levels measured in DBS with the FAVNt (R = 0.88).

Conclusions/Significance

This is the first study that applies DBS for reliable detection of human antibodies against rabies virus. Both the FAVNt and Platelia-II ELISA demonstrate an acceptable performance on DBS, providing opportunities for rabies serology in remote areas. This technique could drastically ease studies evaluating (novel) rabies vaccination strategies and monitoring persisting immunity in humans at risk, living in rabies endemic regions.

Rabies is a nearly 100% fatal disease in humans. However, available vaccines are effective in preventing rabies infection. To investigate if a person is protected against rabies, rabies virus neutralizing antibody levels in the blood are determined. The World Health Organization defines protective immunity as a rabies virus antibody concentration of at least 0.5 IU/ml detected in serum using a virus neutralization test. Yet, in remote areas serum may be rather difficult to collect, process and transport. Whole blood collected with a finger prick and applied on filter paper cards, also known as dried blood spots (DBS), are an easier alternative. This collection method is frequently used for serology of several tropical infectious diseases, but never studied for rabies serology in humans. Therefore, we compared antibody levels measured in serum with those measured in DBS eluates, using the gold standard FAVNt and related it to another commonly used test for human rabies serology, the Platelia-II ELISA. We found that both assays had a good performance on DBS eluates. The reported high specificities provide confidence that unprotected individuals will rarely be missed. Therefore, the DBS is a promising sampling technique for evaluations of vaccination strategies and monitoring persisting immunity after vaccination in populations at risk for rabies.

HIV-1 viral load testing in resource-limited settings: Challenges and solutions for specimen integrity

HIV-1 viral load (VL) testing is a crucial element in providing an antiretroviral treatment monitoring program. The success of these programs depends on the availability and quality of the VL testing services. There are several pre-analytic factors which can affect the quality of VL testing. Many of the challenges faced by resource-limited countries result in a compromise of specimen integrity, thus limiting widespread access to VL monitoring. The various logistic and financial challenges that exist are not insurmountable and several innovative solutions currently exist to overcome these barriers to providing widespread VL testing. This review summarizes the VL testing challenges in resource-limited settings and provides an overview of potential solutions including testing dried blood spots, dried plasma spots, plasma separation cards and the use of point of care tests.

SNAPflex: a paper-and-plastic device for instrument-free RNA and DNA extraction from whole blood

Nucleic acid amplification tests (NAATs), which amplify and detect pathogen nucleic acids, are vital methods to diagnose diseases, particularly in cases where patients exhibit low levels of infection. For many blood-borne pathogens such as HIV or Plasmodium falciparum, it is necessary to first extract pathogen RNA or DNA from patient blood prior to NAAT analysis. Traditional nucleic acid extraction methods are expensive, resource-intensive and are often difficult to deploy to resource-limited areas where many blood-borne infections are widespread. Here, we describe a portable, paper-and-plastic device, called SNAPflex, for instrument-free nucleic acid extraction from whole blood, which builds upon our previous work for RNA extraction using a pressure-driven extraction system. SNAPflex shows improved HIV RNA extraction from simulated patient samples compared to traditional extraction methods as well as long-term stability of extracted RNA without the need for cold storage. We further demonstrated successful extraction and recovery of P. falciparum DNA from cultured parasites in whole blood. SNAPflex was designed to be easily manufacturable and deployable to resource-limited settings.

Uptake of routine viral load testing among people living with HIV and its implementation challenges in Yangon region of Myanmar: a mixed-methods study

OBJECTIVES

In 2017, Myanmar implemented routine viral load (VL) monitoring for assessing the response to antiretroviral therapy (ART) among people living with HIV (PLHIV). The performance of routine VL testing and implementation challenges has not yet assessed. We aimed to determine the uptake of VL testing and factors associated with it among PLHIV initiated on ART during 2017 in ART clinics of Yangon region and to explore the implementation challenges as perceived by the healthcare providers.

DESIGN

An explanatory mixed-methods study was conducted. The quantitative component was a cohort study, and the qualitative part was a descriptive study with in-depth interviews.

SETTING

Six ART clinics operated by AIDS/sexually transmitted infection teams under the National AIDS Programme.

PRIMARY OUTCOME MEASURES

(1) The proportion who underwent VL testing by 30 March 2019 and the proportion with virological suppression (plasma VL <1000 copies/mL); (2) association between patient characteristics and 'not tested' was assessed using log binomial regression and (3) qualitative codes on implementation challenges.

RESULTS

Of the 567 PLHIV started on ART, 498 (87.8%) retained in care for more than 6 months and were eligible for VL testing. 288 (57.8%, 95% CI: 53.3% to 62.2%) PLHIV underwent VL testing, of which 263 (91.3%, 95% CI: 87.1% to 94.4%) had virological suppression. PLHIV with WHO clinical stage 4 had significantly higher rates of 'not being tested' for VL. Collection of sample for VL testing only twice a month, difficulties in sample collection and transportation, limited trained workforce, wage loss and out-of-pocket expenditure for patients due to added visits were major implementation challenges.

CONCLUSIONS

The VL test uptake was low, with only six out of ten PLHIV tested. The VL testing uptake needs to be improved by strengthening sample collection and transportation, adopting point-of-care VL tests, increasing trained workforce, providing compensation to patients for wage loss and travel costs for additional visits.

Monitoring viral load for the last mile: what will it cost?

INTRODUCTION

Routine viral load testing is the WHO-recommended method for monitoring HIV-infected patients on ART, and many countries are rapidly scaling up testing capacity at centralized laboratories. Providing testing access to the most remote populations and facilities (the "last mile") is especially challenging. Using a geospatial optimization model, we estimated the incremental costs of accessing the most remote 20% of patients in Zambia by expanding the transportation network required to bring blood samples from ART clinics to centralized laboratories and return results to clinics.

METHODS

The model first optimized a sample transportation network (STN) that can transport 80% of anticipated sample volumes to centralized viral load testing laboratories on a daily or weekly basis, in line with Zambia's 2020 targets. Data incorporated into the model included the location and infrastructure of all health facilities providing ART, location of laboratories, measured distances and drive times between the two, expected future viral load demand by health facility, and local cost estimates. We then continued to expand the modelled STN in 5% increments until 100% of all samples could be collected.

RESULTS AND DISCUSSION

The cost per viral load test when reaching 80% patient volumes using centralized viral load testing was a median of $18.99. With an expanded STN, the incremental cost per test rose to $20.29 for 80% to 85% and $20.52 for 85% to 90%. Above 90% coverage, the incremental cost per test increased substantially to $31.57 for 90% to 95% and $51.95 for 95% to 100%. The high numbers of kilometres driven per sample transported and large number of vehicles needed increase costs dramatically for reaching the clinics that serve the last 5% of patients.

CONCLUSIONS

Providing sample transport services to the most remote clinics in low- and middle-income countries is likely to be cost-prohibitive. Other strategies are needed to reduce the cost and increase the feasibility of making viral load monitoring available to the last 10% of patients. The cost of alternative methods, such as optimal point-of-care viral load equipment placement and usage, dried blood/plasma spot specimen utilization, or use of drones in geographically remote facilities, should be evaluated.

Optimizing viral load testing access for the last mile: Geospatial cost model for point of care instrument placement

INTRODUCTION

Viral load (VL) monitoring programs have been scaled up rapidly, but are now facing the challenge of providing access to the most remote facilities (the "last mile"). For the hardest-to-reach facilities in Zambia, we compared the cost of placing point of care (POC) viral load instruments at or near facilities to the cost of an expanded sample transportation network (STN) to deliver samples to centralized laboratories.

METHODS

We extended a previously described geospatial model for Zambia that first optimized a STN for centralized laboratories for 90% of estimated viral load volumes. Amongst the remaining 10% of volumes, facilities were identified as candidates for POC placement, and then instrument placement was optimized such that access and instrument utilization is maximized. We evaluated the full cost per test under three scenarios: 1) POC placement at all facilities identified for POC; 2)an optimized combination of both on-site POC placement and placement at facilities acting as POC hubs; and 3) integration into the centralized STN to allow use of centralized laboratories.

RESULTS

For the hardest-to-reach facilities, optimal POC placement covered a quarter of HIV-treating facilities. Scenario 2 resulted in a cost per test of $39.58, 6% less than the cost per test of scenario 1, $41.81. This is due to increased POC instrument utilization in scenario 2 where facilities can act as POC hubs. Scenario 3 was the most costly at $53.40 per test, due to high transport costs under the centralized model ($36 per test compared to $12 per test in scenario 2).

CONCLUSIONS

POC VL testing may reduce the costs of expanding access to the hardest-to-reach populations, despite the cost of equipment and low patient volumes. An optimal combination of both on-site placement and the use of POC hubs can reduce the cost per test by 6-35% by reducing transport costs and increasing instrument utilization.