Rapid Diagnosis of Malaria.
ABSTRACT Malaria's global impact is expansive and includes the extremes of the healthcare system ranging from international travelers returning to nonendemic regions with tertiary referral medical care to residents in hyperendemic regions without access to medical care. Implementation of prompt and accurate diagnosis is needed to curb the expanding global impact of malaria associated with ever-increasing antimalarial drug resistance. Traditionally, malaria is diagnosed using clinical criteria and/or light microscopy even though both strategies are clearly inadequate in many healthcare settings. Hand held immunochromatographic rapid diagnostic tests (RDTs) have been recognized as an ideal alternative method for diagnosing malaria. Numerous malaria RDTs have been developed and are widely available; however, an assortment of issues related to these products have become apparent. This review provides a summary of RDT including effectiveness and strategies to select the ideal RDT in varying healthcare settings.
[show abstract] [hide abstract]
ABSTRACT: The replacement of conventional antimalarial drugs with high-cost, artemisinin-based alternatives has created a gap in the successful management of malaria. This gap reflects an increased need for accurate disease diagnosis that cannot be met by traditional microscopy techniques. The recent introduction of rapid diagnostic tests (RDTs) has the potential to meet this need, but successful RDT implementation has been curtailed by poor product performance, inadequate methods to determine the quality of products and a lack of emphasis and capacity to deal with these issues. Economics and a desire for improved case management will result in the rapid growth of RDT use in the coming years. However, for their potential to be realized, it is crucial that high-quality RDT products that perform reliably and accurately under field conditions are made available. In achieving this goal, the shift from symptom-based diagnosis to parasite-based management of malaria can bring significant improvements to tropical fever management, rather than represent a further burden on poor, malaria-endemic populations and their overstretched health services.Nature Reviews Microbiology 10/2006; 4(9 Suppl):S7-20. · 21.18 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: Several attempts have been made to identify symptoms and signs based algorithms for diagnosing malaria. In this paper, we review the results of published studies and assess the risks and benefits of this approach in different epidemiological settings. Although in areas with a low prevalence the risk of failure to treat malaria resulting from the use of algorithms was low, the reduction in the wastage of drugs was trivial. The odds of wastage of drugs increased by 1.49 (95% confidence limit 1.45-1.51) for each 10% decrease in the prevalence of malaria. In highly endemic areas the algorithms had a high risk of failure to treat malaria. The odds of failure to treat increased by 1.57 (95% confidence limit 1.50-1.65) for each 10% increase in the prevalence. Furthermore, the best clinical algorithms for diagnosing malaria were site-specific. We conclude that the accuracy of clinical algorithms for diagnosing malaria is not sufficient to determine whether antimalarial drugs should be given to children presenting with febrile illness. In highly endemic areas where laboratory support is not available, the policy of offering antimalarial drugs to all children presenting with a febrile illness recommended by the integrated child management initiative is appropriate.Tropical Medicine & International Health 02/2002; 7(1):45-52. · 2.80 Impact Factor
Article: What is clinical malaria? Finding case definitions for field research in highly endemic areas.[show abstract] [hide abstract]
ABSTRACT: In non-endemic areas, the diagnosis of clinical malaria may be made on the basis of fever and a positive blood film. However, in areas of high endemicity, asymptomatic parasitaemia is very common: to assume that a child who presents with fever and parasitaemia is ill from malaria will result in overdiagnosis. In this article, Jo Schellenberg, Tom Smith, Pedro Alonso and Richard Hayes discuss the relationship between fever and parasite density in such areas, and show how the proportion of fevers due to malaria (the attributable fraction) can be estimated and used to evaluate case definitions for use in field trials.Parasitology Today 12/1994; 10(11):439-42.
Hindawi Publishing Corporation
Interdisciplinary Perspectives on Infectious Diseases
Volume 2009, Article ID 415953, 7 pages
RapidDiagnosis of Malaria
ClintonK. Murrayand Jason W.Bennett
Infectious Disease Service, Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, TX 78234, USA
Correspondence should be addressed to Clinton K. Murray, firstname.lastname@example.org
Received 29 January 2009; Accepted 27 April 2009
Recommended by Herbert B. Tanowitz
Malaria’s global impact is expansive and includes the extremes of the healthcare system ranging from international travelers
care. Implementation of prompt and accurate diagnosis is needed to curb the expanding global impact of malaria associated with
ever-increasing antimalarial drugresistance. Traditionally, malaria is diagnosed usingclinical criteriaand/or lightmicroscopy even
though both strategies are clearly inadequate in many healthcare settings. Hand held immunochromatographic rapid diagnostic
tests (RDTs) have been recognized as an ideal alternative method for diagnosing malaria. Numerous malaria RDTs have been
developed and are widely available; however, an assortment of issues related to these products have become apparent. This review
provides a summary of RDT including effectiveness and strategies to select the ideal RDT in varying healthcare settings.
Copyright © 2009 C. K. Murray and J. W. Bennett. This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
According to the World Malaria Report released by the
World Health Organization (WHO) in 2008, there were
247 million malaria cases among 3.3 billion people at
risk in 2006 from 109 countries resulting in an esti-
mated 881,000 deaths. These deaths were primarily in
Africa (91%) and in children under 5 years of age (85%)
. Effective management of malaria per the WHO has
focused on long-lasting insecticidal nets, indoor residual
spraying of insecticide, intermittent preventive therapy
in pregnancy, and artemisinin-based combination therapy
(ACT). Fundamental to improving the care of patients
infected with malaria is prompt and accurate diagno-
sis in order to prevent excess morbidity and mortality
while avoiding unnecessary use of antimalarial agents
and minimizing the spread of resistance to antimalarial
drugs. Diagnostic strategies need to be effective not only
in resource-limited areas where malaria has a substantial
burden on society but also in developed countries where
expertise in the diagnosis of malaria is frequently lacking
Historical strategies to diagnose malaria emphasize clin-
ical diagnostic algorithms, light microscopy, and empiric
therapy. The accuracy of clinical diagnosis, the most com-
monly employed method, is poor, even in countries with
high incidence rates of malaria due to overlapping clinical
symptoms with other tropical diseases and the fact that
coinfections can occur [4–11]. In an era when chloroquine
therapy was widely effective and the primary antimalarial
agent used around the world, definitive diagnosis was not
necessary. Today, given the paucity of effective antimalarial
agents with widespread use of ACT, an increased emphasis
on diagnosis is necessary. This is especially true now
that artesunate failures have been noted . Microscopy
remains the gold standard for detection of malaria para-
sitemia as it can provide information on both the species
of parasite and parasite density of infection . How-
ever, the procedure is labor-intensive and time-consuming,
requiring substantial training and expertise due to fleeting
skills [14–26]. These problems are magnified in nonen-
demic regions where light microscopy to diagnose malaria
is infrequently performed, resulting in missed diagnosis,
misidentification of Plasmodium species, and therapeutic
delays . Methods using advances in technology have
been evaluated as alternatives to light microscopy. While
these methods have varying strengths and weaknesses, they
are limited by equipment, supplies, expertise, cost, time,
2Interdisciplinary Perspectives on Infectious Diseases
applicability in acute infection, and/or availability [13,
New immunochromatographic rapid diagnostic tests
(RDTs) for malaria were introduced in the early 1990s
but have suffered from numerous problems as recently
reviewed [13, 27–31]. Strategies to improve the impact
of malaria RDT have included The Special Programme
for Research and Training in Tropical Diseases which has
introduced principles for development and evaluation
of diagnostic tests for infectious diseases . The
WHO has also undertaken a malaria RDT evaluation
program to improve the overall impact of these tests
(http://www.wpro.who.int/sites/rdt/who rdt evaluation/
accessed 19 January 2009)
Requirements for malaria RDT vary based on malaria
local epidemiology and the goals of a malaria control
program; focusing on performance and operational charac-
teristics (Table 1) [33, 34]. Expectations of an ideal malaria
RDT are minimal operator training, ease of platform with
minimal steps, reproducibility of results, rapid availability of
results (<20 minutes), and low cost. Ideally, the test should
be able to detect recrudescence or relapse and clearance of
parasitemia if therapeutic monitoring is necessary (Table 1).
The WHO has recommended a minimum standard of 95%
sensitivity at parasite densities of 100/uL . In Sub-
Saharan Africa, malaria RDT needs a high sensitivity for
Plasmodium falciparum, but specificity is required to avert
inadequate therapeutic responses when fever is due to other
illnesses, and unnecessary drug pressure. High specificity
and the ability to detect nonfalciparum Plasmodium species
are necessary in low-incidence regions due to low rates
of malaria, and the lower virulence of these species is
conditions require the RDT to be stable under extremes of
temperatures and humidity during use and storage.
Malaria RDT employ lateral flow immunochromatographic
technology similar to rapid pregnancy tests. In these assays,
the clinical sample migrates as a liquid across the surface of a
nitrocellulose membrane by capillary action [13, 27, 33, 34].
For a given targeted parasite antigen, two sets of monoclonal
or polyclonal antibodies are used, a capture antibody and
a detection antibody. Monoclonal antibodies in contrast to
polyclonal antibodies can be very specific but less sensitive.
Also, the source of antigen used (purified native protein,
recombinant proteins, or peptides) can make significant
differences in the performance characteristics of RDT.
The malaria antigens currently used as diagnostic targets
are either specific to a Plasmodium species or are conserved
across all four of the human malaria parasites. Falciparum-
specific monoclonals include histidine-rich protein-2 (HRP-
2) and P. falciparum lactate dehydrogenase (pfLDH) [32,
33]. Targets conserved across all human malaria have been
identified on lactate dehydrogenase (pLDH) and aldolase
HRP-2 is a P. falciparum-specific water-soluble protein,
localized in the parasite cytoplasm and on the surface mem-
brane of infected erythrocyte. It is present on protrusions,
known as knobs, thought to account for sequestration of the
trophozoites and schizonts in postcapillary venules. There is
increasing concentration of HRP-2 as the parasite advances
from ring stage to trophozoite, and it readily diffuses into
the plasma [39, 40]. HRP-2 is predominately found in
the asexual stages, but it is also found in young P. falci-
parum gametocytes. This possibly allows detection at lower
parasitemias and at detectable levels 28 days after clinical
clearance of parasites from patients [41–44]. Therefore, this
antigen has not yet proven valuable in monitoring response
to therapy. Mutants can escape recognition by monoclonal
antibodies and may be responsible for false negative tests
[45, 46]. An assessment of HRP-2 from nineteen countries
revealed that only 84% of P. falciparum could be detected.
Another antigen target to detect sexual and asexual
stage malaria parasites is Plasmodium lactose dehydrogenase
(pLDH), which is the final enzyme in the malaria parasite’s
glycolytic pathway. Monoclonal antibodies against pLDH
can target all human malaria species or can specifically
differentiate P. falciparum or P. vivax . Aldolase, another
key enzyme in the glycosis pathway conserved across all
malaria parasites, can be used as a universal antigen target
[47, 48]. Other antigens have been recognized as possible
components of future diagnostic tests, but evaluations of
P. ovale- or P. malariae-specific antigens have not been
widely tested [38, 49, 50]. Aldolase and pLDH rapidly fall
to undetectable levels after initiation of effective therapy,
however they are expressed in gametocytes, as does HRP-2,
which may allow detection of P. falciparum after the clinical
infection is cleared .
2.1. Available Malaria Rapid Diagnostic Tests. Numerous
reviews have highlighted the rapid turnover of commercially
available products and varying quality control issues in
peer-reviewed journals of independent evaluations have not
existed for many products. In addition, there are numerous
methodological flaws associated with many of the published
evaluations limiting the ability to compare malaria RDT
[13, 27]. The WHO has listed online RDT manufacturers
and distributors. To be included in these summaries requires
evidence of good manufacturing practices as documented by
either compliance with ISO 13485:2003 or 21 CFR 820 from
the US Food and Drug Administration. Overall it appears
that RDTs using HRP-2 are generally more sensitive than
falciparum-specific pLDH for diagnosing infections caused
by P. falciparum when using RDT. However, data assessing
the utility of pLDH and aldolase in nonfalciparum infections
Currently the BinaxNOW?Malaria test kit is the
only US FDA approved kit. It is based upon the HRP-
2 and aldolase antigens (Binax, INC., Inverness Medical
Interdisciplinary Perspectives on Infectious Diseases3
Table 1: Ideal requirements for a malaria rapid diagnostic test (RDT).
Rapid results (<20 minutes)
Easy to use with minimal training and simple instructions
Environmentally stable device (heat, humidity, air movement, lighting) during use and storage
Reproducible results including quality manufacturing
Detect below parasite density of <100 parasites/μL with appropriate specificity
Detects all human malaria
Plasmodium species specific
Able to detect mixed infections
High sensitivity (< 50 parasites/µL)
Able to monitor response to therapy
Stable to 40◦C
Long shelf life
Point-of-care use (CLIA waived)
< $1 per test
Other malaria endemic areas
+++ (if drug-resistant P. falciparum)
Malaria free countries
$1–3 per test
<microscopy (∼ $20/test)
+++ (high priority), + (low priority), − (not necessary), International Conference on Harmonization (ICH); Good Manufacturing Practices (GMP); Clinical
Laboratory Improvement Amendment (CLIA).
Professional Diagnostic, Scarborough, Me, USA). One large
trial revealed an overall sensitivity of 82% . The overall
specificity for P. falciparum was 94% . Again, using the
BinaxNOW Malaria test kit, a second trial primarily assessed
the utility of finger-stick versus venipuncture obtained blood
samples . The finger-stick technique revealed an overall
sensitivity of 100% for P. falciparum and 83% for P. vivax.
Venipuncture produced similar results to fingerstick for the
detection of P. falciparum and P. vivax (Table 2). According
to the package insert, the overall sensitivity and specificity
are 95% and 94% for P. falciparum, 69% and 100% for P.
vivax, respectively (Table 2). The sensitivity for detecting P.
malariae was 44% (7 of 16 positive samples) and 50% for P.
ovale (1 of 2 positive samples), although these numbers were
too small to determine reliable sensitivity and specificity.
Although the kit is not approved for diagnosing mixed P.
falciparum and P. vivax infections, the sensitivity was 94%.
No clear data exists for using RDT to detect a recently
described species of malaria, P. knowlesi, that has been
reported to infect humans .
Overall, the BinaxNOW?Malaria test kit meets many of
the needs required of an ideal malaria diagnostic platform;
however, it has also a number of limitations including the
FDA indications comment that this kit is only for use
in laboratories that have or can acquire blood samples
containing P. falciparum for use as a positive control. It
is also approved for use in the evaluation of symptomatic
patients, with negative results requiring confirmation by
thick and thin smears. Therefore individual clinicians or
patients themselves might not have rapid results to initiate
immediate therapy. Other limitations include the kit’s ability
to detect viable and nonviable malaria organisms, including
gametocytes and sequestered P. falciparum parasites. In some
settings, such as pregnancy, this is possibly advantageous;
however, this prohibits monitoring the level of parasitemia,
which is often used in management decisions. Additionally
this prevents the monitoring of therapeutic response as
antigens persist after elimination of the parasite. Finally,
positive rheumatoid factor has been associated with false
other RDT [13, 27].
2.2. Applicability of Malaria Rapid Diagnostic Tests. It has
been estimated that 16 million RDTs were delivered in
2006 of which 10.8 million were in Africa and 2.8 million
in India . Malaria RDTs are used at almost every level
of the healthcare system. Most of the data supports using
these devices in settings where trained personnel perform
the assay in targeted adult patient populations presenting
with a febrile illness. There is limited data in children .
Among pregnant women, P. falciparum malaria is associated
with placental sequestration of parasites that can reduce the
sensitivity of microscopic diagnosis. In this clinical scenario,
the detection of HRP-2 might improve diagnostic capability
as this antigen is recovered peripherally . However, the
relevance of persistent HRP-2 antigen for up to a month
after therapy is unclear in this setting. Overall, the ideal
setting for these devices would include use by village workers
4Interdisciplinary Perspectives on Infectious Diseases
Table 2: Performance characteristics of the BinaxNOW?malaria kit for Plasmodium falciparum and P. vivax(data obtained from package
Percent sensitivity (95% confidence interval)
100% (96–100%) versus 98.8% (94–100%)
94.7% (93–96%) versus 90.4% (88-92%)
Parasitemia level (per υL)
Venous versus fingerstick samples
Percent sensitivity (95% confidence interval) %)
81.6% (74–87%) versus 80.6% (73–87%)
99.7% (99–100%) versus 99.5% (99–100%)
without formal medical laboratory training, or travelers for
self-diagnosis and treatment; however, there is conflicting
evidence on the utility of RDT in these settings [56–59]. The
diagnosis of P. falciparum has been made on convalescent
serologic (day 14–21 after febrile illness) or post-mortem
assessments, all supporting possible diagnosis after initiation
of empiric therapy [13, 60].
Other possible indications for malaria RDT could
include malaria prevalence surveys; however, they are
insensitive for use in asymptomatic screening and high
throughput detection cannot be achieved with individually
packaged RDT [17, 61–64]. Currently the American Red
Cross does not screen blood donation units for malaria,
instead deferring donations based upon exposure risks.
2.3. Selection of Malaria Rapid Diagnostic Tests. Selection of
specific malaria RDT is based upon region specific criteria
including the expected health benefit, implementation plans,
monitoring process, and cost with a focus on expected
species of infection, level of parasitemia, and treatment
paradigms. Parasitological confirmation of the diagnosis of
malaria is recommended in all cases except for children
under 5 years of age residing in areas of high prevalence of
P. falciparum. It is unclear if the risk of not treating false-
negative tests outweighs the benefits of empiric therapy.
The WHO has typically outlined 3 broad zones for
selecting devices. Zone 1 occurs primarily in Sub-Saharan
Africa and in lowland Papua New Guinea where infections
occur with P. falciparum only or where nonfalciparum
species occur as coinfections with P. falciparum. The HRP-
2-based kits are probably best in this region because of
overall improved antigen detection for P. falciparum. Zone 2
areas in Africa specifically the Ethiopian highlands, where
falciparum and nonfalciparum malaria typically cocirculate.
RDT in these regions will need to distinguish between
falciparum and nonfalciparum infections. Zone 3 contains
areas with nonfalciparum malaria only; including the P.
vivax areas of East Asia and Central America. Here, RDT
antigen detection without a need to detect or differentiate
falciparum. Even in P. falciparum predominate regions, it
is possible for 1–10% of patients to be coinfected including
cases requiring anti-relapse therapy with primaquine .
Although the major burden of malaria is in endemic
countries, malarious regions are frequent destinations
of the roughly 900 million yearly international travel-
ers (www.unwto.org/index.php, accessed 24 January 2009).
These travelers might require management of their malaria
infection while abroad or upon returning home; however,
laboratory personnel in nonendemic regions often lack
experience or expertise in microscopic diagnosis of malaria
. Based upon a large meta-analysis of malaria RDT use
in travelers, RDT may be an effective adjunct to microscopy
in centers without substantial expertise in tropical medicine
[52, 67]. However, expert microscopy is still needed for
species identification and confirmation. Strategies need to
be developed to determine how best to evaluate and field
malaria RDT for use in nonendemic regions and for travelers
who will be on holiday for prolonged periods of time in
highly endemic regions.
Malaria is a life-threatening infection impacting the most
developed countries of the world along with regions of
the world lacking basic healthcare infrastructure. Increasing
burden of disease, emerging antimalarial drug resistance,
and broad implementation of ACT are placing greater
with malaria. Given the difficulty performing microscopy,
especially in endemic areas, alternative diagnostic strategies
are needed. A highly effective RDT could avert over 100.000
malaria related deaths and about 400 million unnecessary
treatments . In addition, it is likely that RDTs will
be cost-effective due to improved treatment and health
outcomes for febrile disease not due to malaria along
with cost savings associated with antimalarial drugs .
Although there is now an FDA approved malaria RDT,
RDTs have limitations to include the inability to detect
mixed infections, all species of Plasmodium, and infections
at low concentrations of parasites, along with an inability to
monitor response to therapy. In addition, in the case of a
negative result, microscopy is still recommended. Therefore
Interdisciplinary Perspectives on Infectious Diseases5
RDTs do not eliminate the need to obtain thick and thin
smears, and maintaining expertise in microscopy is still
a global priority until a new gold-standard is developed.
However, malaria RDTs are ushering in a new era of
diagnosis to improve the overall global healthcare system.
The opinions or assertions contained herein are the private
views of the authors and are not to be construed as official
or reflecting the views of the US Department of the Army,
the US Department of Defense, or the US government. The
authors are employees of the US government and this work
was performed as part of their official duties. As such, there
is no copyright to be transferred.
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