Diagnostic tools for soil-transmitted
helminths control and elimination programs:
A pathway for diagnostic product
Mark D. Lim
*, Simon J. Brooker
, Vicente Y. Belizario, Jr.
, Franc¸oise Gay-Andrieu
, Bruno Levecke
, Lisette van Lieshout
, Graham F. Medley
, Greg Mirams
, Sammy M. Njenga
, Maurice R. Odiere
, Lieven Stuyver
, Jozef Vercruysse
, Johnny Vlaminck
, Judd L. Walson
the Annecy STH diagnostic experts group
1Global Health Division, The Bill & Melinda Gates Foundation, Seattle, United States of America, 2College
of Public Health, University of Philippines, Manila, Philippines, 3bioMe
´rieux, Marcy l’Etoile, France, 4Faculty
of Veterinary Medicine, University of Calgary, Calgary, Canada, 5Faculty of Veterinary Medicine, Gent
University, Merelbeke, Belgium, 6Department of Parasitology, Leiden University Medical Center, Leiden, the
Netherlands, 7Department of Global Health and Development, London School of Hygiene and Tropical
Medicine, London, United Kingdom, 8Jimma University Institute of Health, Jimma, Ethiopia, 9Techion
Group Ltd, Dunedin, New Zealand, 10 Kenya Medical Research Institute, Nairobi, Kenya, 11 Centre for
Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya, 12 Janssen Diagnostics,
Beerse, Belgium, 13 Departments of Global Health, Medicine (Infectious Disease), Pediatrics and
Epidemiology, University of Washington, United States of America, 14 Natural History Museum, London,
¶ Membership of the Annecy STH diagnostic experts group is listed in the Acknowledgments.
The 2020 Roadmap goals endorsed by the World Health Organization (WHO) for soil-trans-
mitted helminths (STHs) (Ascaris lumbricoides,Ancylostoma duodenale,Necator americanus,
Trichuris trichiura) are focused on mass drug administration (MDA) of anthelmintics to con-
trol morbidity associated with moderate- and heavy-intensity infection . As the STH com-
munity approaches the 75% coverage target for preschool- and school-aged children, there is
increasing interest in exploring post-2020 goals that transition from simply monitoring pro-
gram coverage to strengthened monitoring of a program’s impact on transmission of infection
and determining whether enhanced MDA can break STH transmission with minimal risk of
Diagnostics play a critical role in guiding both the deployment of existing STH program
resources and the implementation and evaluation of STH intervention strategies. Currently
used coproscopic methods to detect and quantify STH-specific eggs, such as the Kato-Katz
method, have practical advantages; test kits are inexpensive and relatively easy to perform in
low-resourced field settings. They also have significant disadvantages, including moderate
labor costs, lower than optimal sensitivity, and poor reproducibility in most program settings.
Several academic and small-business efforts continue to develop tools with improved diagnos-
tic performance [5–7]. However, an objective assessment on the value proposition offered by
these tools has been complicated, as the diagnostic needs of a multiphased STH program have
not been defined .
PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.0006213 March 1, 2018 1 / 18
Citation: Lim MD, Brooker SJ, Belizario VY, Jr.,
Gay-Andrieu F, Gilleard J, Levecke B, et al. (2018)
Diagnostic tools for soil-transmitted helminths
control and elimination programs: A pathway for
diagnostic product development. PLoS Negl Trop
Dis 12(3): e0006213. https://doi.org/10.1371/
Editor: Haruhiko Maruyama, Miyazaki Daigaku
Igakubu Daigakuin Ikagaku Kangogaku Kenkyuka,
Published: March 1, 2018
Copyright: ©2018 Lim et al. This is an open access
article distributed under the terms of the Creative
Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in
any medium, provided the original author and
source are credited.
Funding: The authors received no specific funding
for this work.
Competing interests: Three of the coauthors are
employed by commercial companies. Franc¸oise
Gay-Andrieu is employed by bioMerieux, Greg
Mirams is employed by Techion Group Ltd, and
Lieven Stuyver is employed by Janssen
Diagnostics. None of these individuals received any
form of compensation contributing to this
manuscript, nor are any products/patents
developed by their affiliated companies described
within the manuscript.
This report shares a user-centered framework developed by a diverse group of key opinion
leaders convened over the past year by the Bill & Melinda Gates Foundation to define circum-
stances in which population-level diagnostic data could guide an STH program manager’s
decision to transition a program to the next phase. The use-cases and companion target prod-
uct profiles (TPPs) are intended to provide the community with a pathway for the research,
development, evaluation, and implementation of diagnostic tools designed for STH programs.
This framework can also be used to prioritize research or product development resources
based on immediate and anticipated program needs.
Current landscape of STH program diagnostics
The number of adult STH worms harbored by an individual determines both their risk of mor-
bidity and contribution to overall transmission . Worm expulsion studies required to quan-
tify worm burden have suboptimal accuracy, are laborious, and are rarely done. Thus, STH
programs employ indirect methods to infer worm burden, such as microscopy-based technol-
ogies for visual identification and quantification of STH-specific eggs from a stool sample.
WHO recommends the use of the Kato-Katz method, a low-cost, simple, and standardized
tool that provides sufficient sensitivity for morbidity control programs aiming to reduce preva-
lence of moderate- and heavy-intensity infections to less than 1% . A key limitation of the
method is its suboptimal sensitivity, particularly in low transmission settings where egg counts
are typically low . Alternatives to Kato-Katz include the Mini-FLOTAC and McMaster
methods, although these tools lack WHO recommendations for programs and thus have been
limited to research use [5,11–13]. Recent technology development efforts have also focused on
improved analytical sensitivity, such as molecular assays [6,14–17] and enhanced visualization
of helminth eggs [7,18]. Another early area of investigation includes serological and urine-
based measurements [19,20]. However, all these methods potentially incur additional costs-
per-test and resource requirements for STH programs that need to be considered, relative to
the benefits of enhanced efficiency and accuracy . Table 1 highlights other opportunities to
improve coproscopic methods.
Starting from the end: STH diagnostic use-cases and TPPs
Diagnostics are required at different decision points in STH programs, ranging from mapping
endemic geographies to monitoring and evaluation, assessing whether MDA can be stopped,
and post-MDA surveillance . Use-cases depict the link between a specific program deci-
sion to the interpretation of a diagnostic test result, regardless of the technology or method
used to make the measurement . A group of key opinion leaders represented the voice of
the diagnostic user by describing and predicting scenarios faced by STH programs, creating a
Table 1. Limitations and opportunities for improving coproscopy, with the Kato-Katz method as a predicate
• Low sensitivity for very low-intensity infections
• Variable test results impact prevalence
measurements, particularly if eggs are highly clustered
or in low abundance
• Intra-individual variation in egg excretion during
the day and between consecutive days
• Operator-based variability in test results
• Exposure of operator to infectious agents in stool
• Need to process stool samples quickly after
collection, particularly for hookworm analysis
Opportunities for improvement
• Integrated quality control/quality assurance for
preparation (homogenization) and analysis of stool
• Increased throughput
• Electronic connectivity, test results accessible for
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series of problem statements and decisions that each can be addressed by a hypothetical diag-
nostic. Each solution is further detailed in a TPP as a list of technical characteristics, such as
type of measurement and implementation requirements.
One practical use of a TPP is to provide an objective framework for evaluating existing tech-
nologies and innovations to determine opportunities for product development (Table 2). The
breakdown of an STH program into diagnostic use-cases also ensures that research and prod-
uct development resources are aligned with program time lines by considering global progress
of STH programs and goals (controlling morbidity, interruption of transmission), maturity of
technology landscape, and time lines when technologies will be needed. This framework is not
intended to prevent the development of a single technology that addresses multiple use-cases;
however, a platform must meet the requirements described in each of the various TPPs.
Previous works by Solomon et al.  and Hawkins et al.  have provided high-level
TPPs. This report builds on these efforts by providing a more comprehensive framework that
links program decision points to detailed use-cases and TPPs. The diagnostic end user is the
STH program manager who requires a population-wide diagnostic assessment to determine
the transition of a program to the next planned phase. This introduces a unique challenge for
developing diagnostic TPPs for population-based intervention programs, as performance
requirements for individual-level assays are in context of decisions informed by population-
Following previous work , four broad decision points were used to categorize each use-
case against a hypothetical reduction in population-level infection resulting from program
intervention, as shown in Fig 1. Embedded within this illustration is a spectrum of program
Table 2. Planning processes for product development.
Output Objective Stakeholders responsible for definition
Use-cases • Requires understanding of program workflow; infrastructure; resources to identify needs,
preferences, limitations for implementation
• Define link between phase of program and criteria, with implications of diagnostics-based
• Frame epidemiological/biological characteristics
• Identify stakeholders (data users, test implementers, policy, payors)
• WHO STH program guidelines or
With input from:
• Research (laboratory, epidemiology,
TPP • Requires defined use-case
• Define “must-have” criteria for a diagnostic to meet program needs for each use-case
• Assess feasibility of meeting TPP requirements via landscape of existing research/methods/
technologies/available patient specimens
• Define evaluation criteria and methods for assessing new products and regulatory pathway
• Account for cost-effectiveness, scalability, manufacturability
• Product development
With input from:
• WHO STH program guidelines or
• Requires use-case and TPP
• Define regulatory pathway
• Define requirements in accordance with existing or new STH program policies/guidelines/
• Define pathway for translating existing reagents/methods into prototype
• Define verification criteria that prototype meets TPP to lock/freeze design
• Define validation criteria to evaluate adherence to TPP in actual operating conditions
• Define product launch plan
• Define payors/donors for program’s diagnostic infrastructure
• Define user-support, quality assurance, monitoring, supply chain requirements
• Define manufacturing and distribution plans
• Product development
• WHO STH program guidelines or
With input from:
• Country programs
• Representatives from Ministries of
• Program donors
• Implementing nongovernment
Abbreviations: STH, soil-transmitted helminth; TPP, target product profile.
PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.0006213 March 1, 2018 3 / 18
decisions to initiate, continue, suspend, or transition to the next planned program phase, in
the context of a program’s goal of morbidity control or elimination of transmission. Those
decisions that are hypothetically guided by diagnostic test results are described in the algo-
rithm shown in Fig 2 and form the basis of the use-case categories:
•use-case #1. Determine STH transmission and identify type of MDA,
•use-case #2. Assess progress against program goals,
•use-case #3. Confirm a decision to stop intervention and transition to surveillance,
•use-case #4. Verify sustained break in transmission.
An additional level of detail is provided in the spreadsheet within the supplementary mate-
rials of this article (S1 File).
Several factors were considered in prioritizing a diagnostic that confirms a break in trans-
mission (use-case #3). There is strong interest in leveraging the successes of increased MDA
coverage to further reduce STH transmission beyond the level of morbidity control toward
interruption of transmission [2,3]. Achievement of this goal would allow programs to stop
regular MDA with minimal risk of recrudescence, but there currently lacks a reliable tool to
confirm this end point. However, as discussed later, evidence from research is needed to
develop a rigorous TPP for such a diagnostic. On the shorter term, there may be opportunities
to strengthen STH programs by providing access to technologies that are superior to the Kato-
Katz method (Table 1) for monitoring impact on transmission (use-case #2) .
Fig 1. Hypothetical prevalence curve (dots) for a successful STH elimination program, overlaid with program phase (diamond for transition points) and
diagnostic use-cases. MDA, mass drug administration; STH, soil-transmitted helminth.
PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.0006213 March 1, 2018 4 / 18
The development of a TPP for use-case #4 was felt to be premature and not to be pur-
sued until evidence demonstrates that a strategy for sustained interruption of transmis-
sion is feasible and can be scaled for STH programs. The biomarker landscape that would
meet this context of use is also at its early stages, and resources required to implement the
scale and coverage for this type of surveillance infrastructure need to be further defined
Across all use-cases is an option to integrate and leverage the resources of other public
health programs. For instance, many STH programs are integrated with schistosomiasis con-
trol efforts due to co-endemicity [8,26], with the Kato-Katz method also able to detect infec-
tion by Schistosoma mansoni and S.japonicum. Non–stool-based biomarkers may provide
opportunities for simultaneous detection of infection by S.haematobium. Post-elimination
surveillance would likely leverage multiple disease surveillance programs through centralized
Use-case #1—Initiate and determine type of MDA
The assay described in this use-case provides results that identify populations that warrant
MDA and determines the frequency of MDA and the frequency of future monitoring. These
decisions are currently based on measurements of two parasitological indicators in school-
aged children: overall prevalence of any STH infection and proportion of individuals harbor-
ing an infection of moderate to heavy intensity .
The first indicator relies on aggregated results from individual-level diagnostic tests to
determine whether the prevalence of STH infection is below 20%, exceeds 20%, or is 50%
and above. These thresholds have been defined by WHO and are based on fecal egg counts
(FECs) derived from a Kato-Katz measurement to guide an STH control program in not
providing MDA or providing annual or biannual MDA. Because these programs are cur-
rently focused on controlling morbidity from moderate- to heavy-intensity infection, there
are no recommendations for prevalence less than 20%, nor is the Kato-Katz method suitable
for measuring low FEC. However, a “low transmission” category was included in the popu-
lation stratification (Fig 2) in the hypothetical event that STH elimination programs would
be initiated in lower transmission settings and that a tool that detects lighter infections
would be available.
To meet the needs of the second indicator, a test provides individual-level quantitative
results that are combined to estimate the proportion harboring moderate to heavy intensities
of infection by any STH, thresholds currently based on species-specific FEC (Table 3, ).
Fig 2. Diagnostic use-cases, described by program decision algorithm. Dashed box indicates a decision not described under current
WHO guidelines for controlling STH morbidity but that may be important for a program aiming to eliminate transmission of STH. Dx,
diagnostic; KK, Kato-Katz; MDA, mass drug administration; SAC, school-aged children; STH, soil-transmitted helminth.
Table 3. Classes of intensity, based on Kato-Katz measurements .
STH Individual intensity of infection (in eggs per gram of stool)
Light Moderate Heavy
Ascaris lumbricoides 1–4,999 5,000–49,999 50,000
Trichuris trichiura 1–999 1,000–9,999 10,000
Hookworms 1–1,999 2,000–3,999 4,000
Abbreviation: STH, soil-transmitted helminth.
PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.0006213 March 1, 2018 6 / 18
These test results also provide a baseline measurement for monitoring the impact of an inter-
vention, as described in latter use-cases.
Use-case #2—Assess progress against program goals
This use-case applies to STH programs that have initiated intervention and seek to evaluate
progress in reducing prevalence and intensity of infection . By comparing population-level
results from previous or baseline measurements, programs that meet their milestones would
continue the intervention strategy as planned. However, an under-performing program would
conduct additional evaluations to determine potential causes, such as assessments of popula-
tion migration, environment, workforce, drug quality, treatment adherence, and anthelmintic
Decisions made from these quantitative tests are dependent on the type of program and
this use-case was divided into two. Morbidity control programs are initiated in moderate- to
high-prevalence settings and rely on two indicators, overall prevalence of infection by any
STH and the proportion of individuals with moderate and heavy infections (e.g., use-case #2A,
as described in S1 File). An STH program targeting interruption of transmission would initiate
or continue efforts in lower transmission settings and would be focused solely on monitoring
the reduction of overall prevalence (e.g., use-case #2B), because it is unlikely that there will be
any moderately to heavily infected individuals .
The Kato-Katz method provides sufficiently reliable analytical data to meet use-case #2A
and is suitable for morbidity control programs focused on moderately to heavily infected indi-
viduals, but improvements to FEC measurements that address reproducibility and throughput
challenges (Table 1) would enhance program efficiency as well as create opportunities for pro-
grams to proceed beyond morbidity control [30,31]. Technologies that meet the needs of use-
case #2B can also be used in moderate and high transmission settings by STH control pro-
grams but offer greater value in lower transmission settings, where the Kato-Katz method fails
to provide reliable data. For practical considerations, a preferred technology would be a plat-
form that addresses multiple use-cases by meeting the requirements described in each of the
Use-case #3—Confirm a decision to stop intervention and transition to
This use-case applies to programs aiming to interrupt transmission of any STH in low- to
very-low- prevalence settings. In this circumstance, program progress and other transmission
measurements would lead a program manager to initiate a test that confirms that a program
can stop MDA and/or other population-directed interventions. Diagnostic results that confirm
a break in transmission with minimal risk of recrudescence would transition program goals
from active intervention to surveillance for recrudescence (use-case #4) or, in the event of dis-
cordant results, would initiate additional assessments.
The low- to very-low-prevalence threshold that describes the transmission breakpoint is
species specific and has yet to be established, although it can be approximated through mathe-
matical and animal models . Based on studies with A.lumbricoides, worm dynamics
behave differently at low worm burdens compared to high burdens, such that the number of
fertile eggs no longer have a linear relationship to worm burden, making any individual-level
coproscopic measurement unreliable for determining very light intensities of infection rele-
vant to the population-level transmission breakpoint . Nonmicroscopy biomarkers with a
linear relationship to low worm burden, detectable within a dynamic range relevant to the
PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.0006213 March 1, 2018 7 / 18
transmission breakpoint, are needed. Table 4 provides a high-level overview of desired charac-
teristics for any biomarker meeting this use-case.
Use-case #4—Verify sustained break in transmission
This use-case applies to programs that have successfully interrupted STH transmission (use-
case #3) and seek to verify sustained elimination of transmission  or have reason to believe
that there may be a risk of recrudescence. A program would investigate the potential causes of
unexpected results if qualitative test results indicate ongoing transmission. Ideally, the test
detects other diseases under surveillance and requires a specimen that is easier to collect than
stool, such as urine, saliva, or blood, to encourage participation in screening events, with anal-
ysis performed in a centralized laboratory.
The aspirational list of biomarker characteristics described in Table 4 are similar for use-
cases #3 and #4, and stricter definitions warrant further discussion. Similar tests for other dis-
eases have relied on detecting host-response antibodies of infection , a class of biomarker
convenient for integrated surveillance. These biomarkers of host response should ideally be
specific for active infection, not exposure. Alternatively, exposure-based biomarkers could be
measured within indicator subpopulations born after transmission has been broken, as these
groups should not have been exposed to STH infection in geographies remaining absent of
transmission . Although species-specific detection is listed in Table 4, it remains unclear if
a pan-STH biomarker would suffice for this use-case.
Use-cases to TPPs
The TPP describes technical performance and implementation requirements for an assay to
meet the decision needs of a program’s specific use-case. Each requirement is defined in a TPP
as minimal or optimal criteria, reflecting a consensus of accepted compromises. To reduce
risks and time lines for developing a product and accelerating adoption, criteria should con-
sider the capacity, resources, and diagnostic workflows of STH programs in the context of
existing research, methodology, and technology landscape.
Requirements for technology performance and implementation are linked and criteria con-
sider trade-offs for supporting a new test within an existing diagnostic system versus costs for
adapting or creating infrastructure. Implementation considerations include: survey design
(population targeted for testing, sampling size), available workforce, workflow (specimen col-
lection and transportation, sample preparation and analysis), throughput and turnaround
time for test results, data requirements, and criteria for reimbursing test costs. Other consider-
ations include external quality assurance requirements and regulatory pathway as well as pro-
gram recommendations, policies, and guidelines.
Table 4. General desired characteristics of use-case #3 and #4 biomarkers.
• Biomarker measurement correlates to active infection by specific species-level STH
• Biomarker clears within 1 year of last prescribed intervention, in absence of reinfection
• Specific for each STH, no cross-reactivity with other pathogens
• Detected in populations residing in geographies with less than 2% prevalence of any STH infection
• Detected in infected individuals who are Kato-Katz negative
• Sufficient abundance in readily accessible body fluid (nonstool)
• Detection maximizes cost-efficiencies (e.g., amenable to pooling, simplified collection and shipment, testing in
young children born after presumed transmission breakage)
• Easily translatable to accessible diagnostic platforms
Abbreviation: STH, soil-transmitted helminth.
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Because diagnostics only approximate a true state of infection, mathematical models can be
used to further inform performance requirements by estimating the impact of different levels
of uncertainty on the accuracy of program decision-making and ultimately on health out-
comes . Models can also provide a health economics framework to justify performance
requirements by weighing the predicted health outcomes against costs incurred by a program
to conduct a survey as well as resources deployed in the event of an incorrect decision .
Minimum criteria describe performance characteristics that must be achieved for a test to
be used by most STH programs. Optimal criteria describe attributes that expand the value of
the assay but would not be required by most STH programs. Simply, minimum criteria
describe “must-have” requirements, whereas “nice-to-have” options are listed as optimal,
details that guide product development and evaluation priorities as well as resource allocation.
In addition to setting targets for technology development, these requirements are also criteria
for clinical and field trials and should consider availability and access to patient specimens
from geographies representing the epidemiological and individual context of intended-use
populations. These specimens must naturally represent the diversity and range of biomarkers
to validate the performance claims of a prototype assay, with appropriate analytical and clinical
benchmarks. Excessive technical complexity beyond actual program needs should be avoided,
as each claim needs to be validated with available patient samples.
For example, qualitative yes/no results may be a sufficient level of detail that most programs
require from a test result, such as presence or absence of transmission within a population
(e.g., use-case #3). In this instance, the minimum requirement listed in a TPP would be a quali-
tative test result, for interpretation by a program manager. It is important to differentiate the
presentation of a test result from the method of analysis, as this qualitative output could be
derived from the quantitative analysis of aggregated individual-level data or pooled specimens.
If some programs have the resources and capacity to also act on test results that provide spe-
cies-specific intensities of infection, then quantitation could be listed as optimal criteria. How-
ever, validating that a test reliably provides quantitative test results for each STH species also
requires access to statistically powered quantities of accessible patient specimens that contain
the natural dynamic range of intensities for each STH.
As mentioned earlier, the use-case for monitoring program impact was divided into two
similar use-cases, #2A and #2B, to address programs that intend to reduce transmission
beyond morbidity control (S1 File). However, a TPP for use-case #2B was not developed, as a
lower limit of detection (LOD) would approximate the transmission breakpoint, a species-spe-
cific indicator that requires further definition. At these lower transmission settings, a program
manager might be solely interested in prevalence, unlike morbidity control programs, in
which intensities of infection are an additional program metric.
Two TPPs were developed and finalized by this group of STH stakeholders. Use-cases #1
and #2A were combined because there is little demand for a diagnostic dedicated to use-case
#1, with the current pace of coverage by STH programs (S2 File). Diagnostic tools that address
both use-cases would likely be similar, given the current landscape of coproscopy technologies.
There was agreement on current WHO recommendations for using the Kato-Katz method in
morbidity control programs, but this technique would not meet all requirements described in
this new TPP. With an intent to strengthen a program’s ability to monitor impact, new diag-
nostic products must satisfy all minimum requirements described in this joint TPP.
The second TPP described a tool to confirm a sustained break in transmission, a use-case
that only requires a qualitative test result (S3 File). Conceptually, a platform that meets the
needs of use-case #3 might also satisfy use-case #1–#2 if the test offered quantitative test results
with appropriate upper limits of quantitation, but this warrants further discussion in the
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context of this type of multi-parametric test result. The complete TPPs are available as supple-
mental materials that accompany this article, with key sections for use-case #3 discussed
Discussion on select components of use-case #3 TPP—Confirming break in
Section 1: Intended use. This diagnostic confirms that transmission of each STH has
been sustainably suppressed below its breakpoint, a qualitative population-level test result pro-
vided by statistical analysis of pooled specimens or data aggregated from multiple individual-
level tests. A negative test result confirms the decision to wind down an active intervention
and transition program goals to surveillance for recrudescence (use-case #4). A positive test
result indicates that transmission has not been broken, requiring the program to investigate
causes of confounding results. An STH program manager would use this test when other met-
rics indicate that the intervention has likely met its end point and seeks confirmation with a
diagnostic survey of a targeted population. These nondiagnostic indicators to initiate testing
have yet to be defined and will be clarified through ongoing research assessing the strategy for
interrupting transmission .
The minimum detection requirement is species-level infection by A.lumbricoides,T.tri-
chiura, and hookworms (A.duodenale,N.americanus). Hookworm differentiation is not
required because interventions are the same for the two species. However, some STH pro-
grams or the research community may be interested in differentiation between A.duodenale
and N.americanus or detection of infections by A.ceylanicum and Strongyloides stercoralis,
and these possibilities were listed as optimal criteria. It was noted that neither infections by A.
ceylanicum nor S.stercoralis are treated by MDA-based interventions . In addition to
hookworms, optimal requirements also considered integration of STH programs with those
focused on controlling schistosomiasis (S.mansoni,S.japonicum, and S.haematobium) [1,26].
The intended use of this assay also describes the ideal scenario for implementing a test.
These details are described in Section 4 of the TPP and must be realistic to the workflow and
resources available to an STH program. These considerations also define criteria for additional
methods and accessories required to support the use of the test, such as those for specimen col-
lection and preservation. Health economics and community-acceptability studies that provide
a cost-effectiveness and implementation framework for elimination programs are needed to
determine the ideal diagnostic scenario.
Section 2: Population needs and performance characteristics. The results from a test
meeting the needs of use-case #3 provide an indicator of worm and population dynamics to
determine if an intervention has reduced parasite reproduction to a point at which local
extinction is highly probable (i.e., transmission breakpoint) . In this use-case, criteria for
clinical sensitivity is based on an individual’s intensity of infection in relation to this transition
point in transmission dynamics, with a true positive test result identifying an individual who is
transmitting any STH infection . Phenotypic characteristics related to the number of worms
harbored by an individual who would be classified as positive under this use-case remain unde-
fined, as individuals classified as test negative may still be infected with STH but not contribut-
ing to transmission. Early-stage research is aimed at developing biomarkers that are fit for this
context of use and can be measured in non–stool-based specimens. As with any biomarker-
based measurement, it is important to assess the reliability of results by addressing potential
sources of interindividual variability, including age, nutritional status, and social dynamics.
These variables might be approximated by mathematical and animal modeling to guide bio-
marker and epidemiological research . The early-stage nature of these investigations is
PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.0006213 March 1, 2018 10 / 18
reflected in this version of the TPP and is subject to updates, as additional evidence justifies a
rigorous performance requirement.
Analytical sensitivity describes technical performance of the assay (e.g., with spiked sam-
ples) and defines the required minimum concentrations of a target analyte that must be mea-
sured reliably (95% confidence). Only the lower LOD needs to be defined for a qualitative test
and set below the confidence intervals for a diagnostic cutoff. Since this cutoff cannot yet be
defined, key opinion leaders agreed that a test must have superior analytical sensitivity com-
pared to current FEC methods. Given the current lack of validated analytical comparators in
this range of light infection, in the interim, the LOD was defined as less than 1 egg per 41.7 mg
of homogenized stool (equivalent to 24 eggs per gram). This section will be updated in future
TPPs as evidence becomes available to justify an appropriate unit of measurement related to
clinically relevant diagnostic cutoffs for this use-case, with validated analytical benchmarks
that are not egg-based measurements or limited to stool samples.
Quality control requirements address confidence in test results and consider costs for inte-
grating controls within an individual assay as well as costs and resources for external assess-
ments. For stool-based specimens, there was consensus that individual assays require internal
controls as a pre-analytical assurance that stool samples were uniformly homogenized and pre-
pared, addressing some of the challenges described in Table 1. There was also agreement that
external quality assessment programs would be needed to ensure that STH testing locations
that likely vary in infrastructure and workforce are providing consistent results [42,43].
Section 3: Regulatory and statutory needs. The regulatory pathway for global health
diagnostics was not defined when the Kato-Katz method was recommended by WHO in 1985
for schistosomiasis control programs . This method would likely not have passed current
regulatory requirements if introduced today, given the risk of variable test results and lack of
quality control. There was consensus that quality results and reproducibility will be required
for any new tests and that these products must be developed using design-control processes
 and standards defined by ISO13485 . The latter is an internationally recognized stan-
dard for developing medical devices through documented processes that ensure consistent
attention to quality considerations, from design and development to manufacture and
In addition to adherence to International Organization for Standardization (ISO) processes,
the product-development process will also be defined by the regulatory labeling of the tool for
research use only (RUO), investigational use only (IUO), or as an in vitro diagnostic (IVD).
Beyond ISO and design control requirements, the regulatory pathway for this assay is currently
not known and will be updated in future TPPs.
Tests that guide individual-level treatment decisions are typically classified as IVDs and
may also require WHO’s prequalification (PQ) for use in global health settings, in addition to
clearance by stringent national regulatory authorities, before they can be procured and used
within a program . Unlike traditional IVDs, STH programs do not make individual-level
treatment decisions but instead focus on MDA with albendazole or mebendazole. The assay
described in use-cases #1 and #3 guide treatment decisions that have population health impli-
cations for correct and incorrect results; premature cessation of population-based treatment
could result in recrudescence . An alternative consequence is overtreatment and wasted
program resources. These types of assays would likely be developed following a regulatory
pathway for an IVD, whereas RUO may be suitable for use-cases #2 and #4.
Future discussions are needed to determine the regulatory pathway of tests described in all
four use-cases. One important consideration is the implication of a decision based on an incor-
rect test result and steps to mitigate unintended health outcomes. For use-case #3, an increased
risk of recrudescence due to premature wind-down of a program might be mitigated if tests
PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.0006213 March 1, 2018 11 / 18
described in use-case #4 are in place and populations remain under surveillance. Likewise, an
increased risk of overtreatment due to late wind-down of a program might be mitigated if
monitoring tests described in use-case #3 are in place. For use-cases #2 and #4, if the intended
purpose of monitoring and surveillance tests is to trigger confirmatory testing or initiate test-
ing to investigate inconsistent results, then these assays would only guide program testing, not
treatment decisions. These hypothetical scenarios exemplify the intertwining nature of pro-
gram guidelines with the regulatory pathway for developing an assay.
Section 4: Healthcare/program system needs. This section includes requirements for the
successful implementation of a diagnostic. Because targeted population-level data are required
for the program decision, minimum data requirements also include geospatial information.
There was no advantage for receiving the test result at the point of contact (e.g., rapid diagnos-
tic test) because population-level data is required for program decisions, with acceptable turn-
around time for results being over a period of weeks and months.
For the testing environment, key opinion leaders agreed that the testing site should be in
proximity to a community or school, preferably at a district-level health center or through a
mobile van campaign, to increase community participation and adherence in MDA events.
This was based on reports of community involvement in improving the health outcome
provided by MDA, particularly because STH infection is predominantly driven by an indi-
vidual’s interaction with their local environment, including access to clean water and sanita-
tion [49,50]. The global neglected tropical disease (NTD) agenda is also aligned with aims
to strengthen general healthcare services within impoverished communities, increasing
opportunities for developing an STH diagnostic on platforms that address other community
health needs .
District-level settings often have sufficient resources to perform simple diagnostic tests,
such as microscopy or rapid diagnostic tests, with access to running water and sufficient elec-
tricity during test operation and at least one individual who can be trained to perform a simple
test. These settings rarely have sterile work stations and minimal biosafety resources; thus,
TPP requirements address the safety of the test operator and local environment by reducing
exposure to biospecimens and reagents through design (e.g., self-containment and safety lock)
as well as simple disposal processes. Optimal requirements would be met if the test did not
require consistent electricity to operate, such as through a battery, and thus were operational
in less-resourced settings.
The success of the current WHO STH control strategy has catalyzed interest in moving beyond
coverage estimates and morbidity control to improving program efficiency and exploring the
prospect of breaking the transmission of STHs to reduce resources required for sustaining ver-
tical STH programs. These aspirations require surveys of the targeted populations, and the aim
of the hypothetical use-cases was to simulate STH program decisions requiring diagnostic
information. The context within these use-cases frame performance and implementation
requirements for the design and evaluation of existing and new tools. This approach ensures
that user needs are the destination of a research and product development road map, instead
of forcing the adoption of an imperfect technology. In the best-case scenario, one technology
is able meet the requirements of multiple TPPs.
The current TPP for use-case #1 and #2A addresses the needs of morbidity control pro-
grams but does not address the needs of elimination programs that would initiate or continue
in lower transmission settings (e.g., <20% apparent prevalence). The Kato-Katz method meets
most, but not all, of the minimum criteria in this TPP, as it offers sufficient analytical and
PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.0006213 March 1, 2018 12 / 18
clinical sensitivity but does not meet precision and reproducibility criteria (§2.5 and 2.6), nor
does it meet regulatory requirements (§3.1). New tools that meet all requirements described in
this TPP are needed as one step towards strengthening STH program efficiency. Opportunities
for improvement are also highlighted in Table 1, and as with any new tool, it is important to
consider manufacturability, use, and cost-effectiveness from the program perspective.
STH programs that aim to move beyond morbidity control towards interruption of trans-
mission are described in use-cases #2B, #3, and #4. Tests for use-case #2B will require a lower
LOD than use-case #2A, but there is insufficient information to provide definitive criteria, as
this approximates the transmission breakpoint. There is a need to define the epidemiological
characteristics of a transmission breakpoint to understand the risk criteria of an individual’s
contribution to STH transmission within a given population. This is challenging given the
wide range of contextual factors that define population heterogeneity, such as seasonality, indi-
vidual health/nutritional status, environmental exposure, and/or social behaviors. These fac-
tors may influence STH transmission and thus, also, breakpoints . Mathematical modeling
and animal studies can approximate the extent of these potential contributions to guide defini-
tions of phenotypic characteristics (§2.1), information necessary for defining clinical utility
requirements of biomarkers. A TPP for use-case #2B and #3 diagnostics also requires proof of
concept that programs can interrupt transmission in a scalable and cost-effective manner, with
a strategy that verifies decision points requiring diagnostic surveys and test implementation
scenarios (timing, sampling size, etc.).
Diagnostic needs will adjust over time as emerging research continues to evolve program
strategies. These TPPs and use-cases are living documents that capture the current trajectory
of STH programs to identify gaps that can be addressed through research and product
Key learning points
• The soil-transmitted helminth (STH) community has started exploring opportunities
to strengthen a control program’s ability to monitor changes in prevalence of infec-
tion, potentially to a reduction that is sustained below transmission breakpoints.
• Current global strategies have been successful with existing diagnostics, and more
ambitious program end points would likely require different tools to evaluate the
impact of population-directed interventions.
• Newly created target product profiles (TPPs) described in this article aim to direct the
development and evaluation of diagnostic tools that improve the efficiency of control
and elimination programs.
• The STH community lacks a tool to confirm a break in transmission, and based on the
new TPP, critical evidence to inform the development of this diagnostic is currently
unavailable. Additional research is needed to define species-specific transmission
breakpoints and guide the translation of individual-level test results to population-
level transmission indicators.
PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.0006213 March 1, 2018 13 / 18
S1 File. Overview of diagnostics use-cases for STH control and elimination programs.
STH, soil-transmitted helminth.
S2 File. Target product profile for STH use-case #1 and #2A diagnostic (mapping, moni-
toring population-level intervention). STH, soil-transmitted helminth.
S3 File. Target product profile for STH use-case #3 diagnostic (confirming decision to stop
population-level intervention). STH, soil-transmitted helminth.
Members of Annecy STH diagnostic experts group, Fondation Me
´rieux Les Pensières Center
for Global Health, Annecy, France, are:
Hafid Abaibou, bioMe
Vicente Belizario, University of Philippines, Manila, Philippines,
Mark Bradley, GlaxoSmithKline, UK,
Simon Brooker, Bill & Melinda Gates Foundation, USA,
Donald Bundy, Bill & Melinda Gates Foundation, USA,
Dan Campbell, Dan Campbell Consulting, USA,
William Colon, Janssen Diagnostics, Belgium,
Lauren Cutright, Bill & Melinda Gates Foundation, USA,
Marc Engelen, Janssen Diagnostics, Belgium,
Franc¸oise Gay-Andrieu, bioMe
Cristina Giachetti, Bill & Melinda Gates Foundation, USA,
John Gilleard, University of Calgary, Canada,
Jiagang Guo, NTD Department, World Health Organization, Switzerland,
John Hawdon, George Washington University, USA,
Deirdre Hollingsworth, University of Warwick, UK,
Sunny Jiang, University of California, Irvine, USA,
Peter Jourdan, Natural History Museum, UK,
Karine Kaiser, bioMe
Stella Kepha, London School of Hygiene and Tropical Medicine/Kenya Medical Research
Marianna Kim, BioFire Defense, USA,
Alejandro Krolewiecki, Universidad Nacional de Salta/Fundacion Mundo Sano, Argentina,
Zeleke Mekonnen, Jimma University, Ethiopia,
Bruno Levecke, Ghent University, Belgium,
Mark D. Lim, Bill & Melinda Gates Foundation, USA,
James McCarthy, QIMR Berghofer Medical Research, Australia,
Graham Medley, London School of Hygiene and Tropical Medicine, UK,
Rojelio Mejia, Baylor College of Medicine, USA,
Greg Mirams, Techion Group Limited, New Zealand,
Antonio Montresor, NTD Department, World Health Organization, Switzerland,
Molly Mort, Bill & Melinda Gates Foundation, USA,
PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.0006213 March 1, 2018 14 / 18
Sammy Njenga, Kenya Medical Research Institute, Kenya,
Maurice Odiere, Kenya Medical Research Institute, Kenya,
Kendra Palmer, Bill & Melinda Gates Foundation, USA,
Laura Rinaldi, University of Napoli Federico II, Italy,
Christine Rozand, bioMe
James Rudge, London School of Hygiene and Tropical Medicine, UK,
Steven Silber, Johnson & Johnson, Global Public Health, USA,
Erin Stuckey, Bill & Melinda Gates Foundation, USA,
Lieven Stuyver, Janssen Diagnostics, Belgium,
Rebecca Traub, The University of Melbourne, Australia,
Jurg Utzinger, Swiss Tropical and Public Health Institute, Switzerland,
Lisette van Lieshout, Leiden University Medical Center, the Netherlands,
Jozef Vercruysse, Ghent University, Belgium,
Johnny Vlaminck, Ghent University, Belgium,
Judd Walson, University of Washington, USA, and Natural History Museum, London, UK,
Joanne Webster, Royal Veterinary College, University of London, UK,
Steven Williams, Smith College and University of Massachusetts, USA.
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