Evaluation of the Clearview® Malaria pLDH Malaria Rapid Diagnostic Test in a non-endemic setting

The Laboratory Diagnosis of Malaria: A Focus on the Diagnostic Assays in Non-Endemic Areas

Even if malaria is rare in Europe, it is a medical emergency and programs for its control should ensure both an early diagnosis and a prompt treatment within 24-48 h from the onset of the symptoms. The increasing number of imported malaria cases as well as the risk of the reintroduction of autochthonous cases encouraged laboratories in non-endemic countries to adopt diagnostic methods/algorithms. Microscopy remains the gold standard, but with limitations. Rapid diagnostic tests have greatly expanded the ability to diagnose malaria for rapid results due to simplicity and low cost, but they lack sensitivity and specificity. PCR-based assays provide more relevant information but need well-trained technicians. As reported in the World Health Organization Global Technical Strategy for Malaria 2016-2030, the development of point-of-care testing is important for the improvement of diagnosis with beneficial consequences for prompt/accurate treatment and for preventing the spread of the disease. Despite their limitations, diagnostic methods contribute to the decline of malaria mortality. Recently, evidence suggested that artificial intelligence could be utilized for assisting pathologists in malaria diagnosis.

Evaluating the efficacy of rapid diagnostic tests for imported malaria in high income countries: A systematic review

BACKGROUND

Malaria is a life-threatening disease. Prior to the pandemic, over a million people annually from non-endemic, high income countries such as Europe and North America visited countries with a risk of malaria transmission. Emergency care nurses in non-endemic countries frequently encounter returning travellers, presenting with symptoms suggestive of malaria. While rapid diagnostic tests are used in countries with endemic malaria, in countries such as the United Kingdom diagnosis is undertaken by microscopy and three negative tests are required to exclude.

QUESTION

Are rapid diagnostic tests effective for diagnosing imported malaria in non-endemic, high income countries?

METHOD

A systematic review of published research (January 2009 - November 2020) comparing rapid diagnostic tests with microscopy.

RESULTS

Fourteen studies were included, conducted in five countries with 14 different RDTs evaluated. Mean sensitivity and specificity for Plasmodium Falciparum was 91.8% and 97.7% and Plasmodium Vivax 81.6% and 99.2%. Higher sensitivities were related to higher parasite densities.

CONCLUSIONS

International travel will return post-pandemic and rapid, accurate and cost-efficient tests will be required. The rapid diagnostic tests in these studies showed significant variation and were not as accurate as microscopy. Consequently, it cannot be recommended that rapid diagnostic tests replace the gold standard of microscopy. Further research is required.

Evaluation of the combination of rapid diagnostic tests and microscopy for imported malaria surveillance in Anhui Province, China

BACKGROUND

In the Anhui Province, China, efforts to interrupt the local malaria transmission were successful, with no endemic cases reported since 2014. Contrastingly, imported malaria cases are still being reported, indicating a disease reintroduction risk after years of elimination. A good surveillance system is key for avoiding the risk, detecting imported cases and possible cases associated with local transmission early. Therefore, rapid diagnostic tests (RDTs) were combined with microscopy to strengthen malaria surveillance in the province. Herein, we aimed to evaluate the efficacy of this surveillance strategy.

METHODS

We conducted a retrospective study using malaria surveillance data from January 2016 to June 2020. Epidemiological characteristics and diagnostic information were analysed using descriptive and comparative statistics. The diagnostic performance of the combined toolbox (Wondfo RDTs plus microscopy) was evaluated based on its sensitivity, specificity, positive and negative predictive values, and Cohen's kappa coefficient, using real-time polymerase chain reaction as the gold standard.

RESULTS

The combined toolbox displayed a higher overall sensitivity for malaria cases than that of microscopy alone (93.74% vs 89.37%; p_adj <0.05), which could detect 94.65%, 88.16%, 95.00%, and 100.00% of Plasmodium falciparum, P. ovale, P. vivax, and P. malariae infections, respectively. In clinical practice, Wondfo RDTs ability to detect P. falciparum infections was better than that of microscopy (97.55% vs 89.67%, p_adj < 0.05). In contrast, microscopy displayed a higher specificity than that of Wondfo RDTs (81.82% vs 63.28%, p _adj <0.05). Moreover, the consistency between microscopy and the gold standard results was also better than that of RDTs (Kappa value:0.669 vs 0.596).

CONCLUSIONS

The combination of microscopy and RDTs is an effective strategy for malaria surveillance because it possibly detected more P. falciparum infections due to the introduction of RDTs. In contrast, microscopy is complementary to some limitations related to the use of RDTs in field practice. Thus, monitoring malaria cases in non-endemic areas may require employing more than one diagnostic tool in surveillance strategies. Moreover, further understanding of the advantages and disadvantages of different detection methods is necessary for applying optimum combinations in field settings.

Evaluating the implementation of rapid diagnostic tests in a malaria elimination setting

Background

It was recommended that malaria rapid diagnostic tests (RDTs) should be available in all epidemiological situations. But evidence was limited on the implementation of RDTs and its effectiveness in malaria elimination settings. This study examined the implementation of RDTs and how it affected the diagnosis of imported malaria patients in Jiangsu Province, China.

Methods

To scale up RDTs, this study developed an intervention package with four major elements covering the supply of RDT test, the training on RDTs, the monitoring and management of RDT use, and the advocacy of RDTs. By using a pretest-posttest control group design, we implemented the interventions in 4 cities in Jiangsu Province with the rest nine cities as controlled areas, from January 2017 to January 2018. Difference-in-Difference approach was used to evaluate the impact of the scale-up of RDTs on the identification of malaria cases. Three binary outcome measures were included to indicate delayed malaria diagnosis, malaria cases with confirmed malaria diagnosis at township-level institutions, and severe malaria cases, respectively. Linear probability regression was performed with time and group fixed effects and the interaction term between time and group.

Results

Intervention areas received sufficient RDT test supply, regular professional training programs, monthly tracking and management of RDT supply and use, and health education to targeted population. The implementation of interventions was associated with 10.8% (P = 0.021) fewer patients with delayed diagnosis. But intervention areas did not see a higher likelihood of having confirmed diagnosis from township-level institutions (coefficient = -0.038, P = 0.185) or reduced severe malaria cases (coef. = 0.040, P = 0.592).

Conclusions

The comprehensive package of RDT implementation in this study is promising in scaling up RDT use and improving access to care among malaria patients, especially in malaria elimination settings.

A new high-resolution melting analysis for the detection and identification of Plasmodium in human and Anopheles vectors of malaria

Among vector-borne diseases malaria is the leading cause of morbidity in the world, with more than 200 million cases per year and a large number of deaths. The techniques traditionally used for the detection of Plasmodium in humans and Anopheles mosquitoes include microscopy, IRMA, ELISA, antibody or molecular assays, and anopheline dissection. However, these techniques are limited by their requirement of skilled personnel, low sensitivity or long processing times. A PCR-based high-resolution melting (PCR-HRM) analysis was developed for the detection and identification of P. falciparum, P. vivax and P. malariae that infect humans and Anopheles. In 41 human samples PCR-HRM detected 14 samples positive for P. vivax, 17 for P. falciparum, three for P. malariae, three mixed infections for P. vivax/P. malariae and four negative samples. Whereas benchmarking assays of microscopy and nested PCR had false positive detections. Additionally, PCR-HRM was able to detect natural infection with Plasmodium spp. in An. darlingi and An. mattogrossensis. The PCR-HRM presented is the first single assay developed for the detection and identification of P. vivax, P. falciparum and/or P. malariae in human and Anopheles. This method improves on currently available assays as it is easy-to-use, rapid, sensitive and specific with a low risk of contamination.

Molecular diagnosis of Plasmodium ovale by photo-induced electron transfer fluorogenic primers: PET-PCR

Accurate diagnosis of malaria infections continues to be challenging and elusive, especially in the detection of submicroscopic infections. Developing new malaria diagnostic tools that are sensitive enough to detect low-level infections, user friendly, cost effective and capable of performing large scale diagnosis, remains critical. We have designed novel self-quenching photo-induced electron transfer (PET) fluorogenic primers for the detection of P. ovale by real-time PCR. In our study, a total of 173 clinical samples, consisting of different malaria species, were utilized to test this novel PET-PCR primer. The sensitivity and specificity were calculated using nested-PCR as the reference test. The novel primer set demonstrated a sensitivity of 97.5% and a specificity of 99.2% (95% CI 85.2–99.8% and 95.2–99.9% respectively). Furthermore, the limit of detection for P. ovale was found to be 1 parasite/μl. The PET-PCR assay is a new molecular diagnostic tool with comparable performance to other commonly used PCR methods. It is relatively easy to perform, and amiable to large scale malaria surveillance studies and malaria control and elimination programs. Further field validation of this novel primer will be helpful to ascertain the utility for large scale malaria screening programs.

Rapid diagnostic tests for diagnosing uncomplicated non-falciparum or Plasmodium vivax malaria in endemic countries

BACKGROUND

In settings where both Plasmodium vivax and Plasmodium falciparum infection cause malaria, rapid diagnostic tests (RDTs) need to distinguish which species is causing the patients' symptoms, as different treatments are required. Older RDTs incorporated two test lines to distinguish malaria due to P. falciparum, from malaria due to any other Plasmodium species (non-falciparum). These RDTs can be classified according to which antibodies they use: Type 2 RDTs use HRP-2 (for P. falciparum) and aldolase (all species); Type 3 RDTs use HRP-2 (for P. falciparum) and pLDH (all species); Type 4 use pLDH (fromP. falciparum) and pLDH (all species).More recently, RDTs have been developed to distinguish P. vivax parasitaemia by utilizing a pLDH antibody specific to P. vivax.

OBJECTIVES

To assess the diagnostic accuracy of RDTs for detecting non-falciparum or P. vivax parasitaemia in people living in malaria-endemic areas who present to ambulatory healthcare facilities with symptoms suggestive of malaria, and to identify which types and brands of commercial test best detect non-falciparum and P. vivax malaria.

SEARCH METHODS

We undertook a comprehensive search of the following databases up to 31 December 2013: Cochrane Infectious Diseases Group Specialized Register; MEDLINE; EMBASE; MEDION; Science Citation Index; Web of Knowledge; African Index Medicus; LILACS; and IndMED.

SELECTION CRITERIA

Studies comparing RDTs with a reference standard (microscopy or polymerase chain reaction) in blood samples from a random or consecutive series of patients attending ambulatory health facilities with symptoms suggestive of malaria in non-falciparum endemic areas.

DATA COLLECTION AND ANALYSIS

For each study, two review authors independently extracted a standard set of data using a tailored data extraction form. We grouped comparisons by type of RDT (defined by the combinations of antibodies used), and combined in meta-analysis where appropriate. Average sensitivities and specificities are presented alongside 95% confidence intervals (95% CI).

MAIN RESULTS

We included 47 studies enrolling 22,862 participants. Patient characteristics, sampling methods and reference standard methods were poorly reported in most studies. RDTs detecting 'non-falciparum' parasitaemiaEleven studies evaluated Type 2 tests compared with microscopy, 25 evaluated Type 3 tests, and 11 evaluated Type 4 tests. In meta-analyses, average sensitivities and specificities were 78% (95% CI 73% to 82%) and 99% (95% CI 97% to 99%) for Type 2 tests, 78% (95% CI 69% to 84%) and 99% (95% CI 98% to 99%) for Type 3 tests, and 89% (95% CI 79% to 95%) and 98% (95% CI 97% to 99%) for Type 4 tests, respectively. Type 4 tests were more sensitive than both Type 2 (P = 0.01) and Type 3 tests (P = 0.03).Five studies compared Type 3 tests with PCR; in meta-analysis, the average sensitivity and specificity were 81% (95% CI 72% to 88%) and 99% (95% CI 97% to 99%) respectively. RDTs detecting P.vivax parasitaemiaEight studies compared pLDH tests to microscopy; the average sensitivity and specificity were 95% (95% CI 86% to 99%) and 99% (95% CI 99% to 100%), respectively.

AUTHORS' CONCLUSIONS

RDTs designed to detect P. vivax specifically, whether alone or as part of a mixed infection, appear to be more accurate than older tests designed to distinguish P. falciparum malaria from non-falciparum malaria. Compared to microscopy, these tests fail to detect around 5% ofP. vivax cases. This Cochrane Review, in combination with other published information about in vitro test performance and stability in the field, can assist policy-makers to choose between the available RDTs.

Performance of Rapid Diagnostic Tests for Plasmodium ovale Malaria in Japanese Travellers

Background: Rapid diagnostic tests (RDTs) are used widely in the diagnosis of malaria. Although the effectiveness of RDTs for malaria has been described in many previous studies, the low performance of RDT particularly for Plasmodium ovale malaria in traveller has rarely been reported.

Methods: This was a retrospective cohort study conducted on Japanese travellers diagnosed with malaria at the National Center for Global Health and Medicine between January 2004 and June 2013. The diagnosis of malaria was confirmed by microscopic examination, RDT, and polymerase chain reaction in all patients. The RDTs used in our study were Binax NOW Malaria (Binax Inc., Scarborough, Maine, USA) (BN) and SD Malaria Antigen Pf/Pan (Standard Diagnostics Inc., Korea) (SDMA). We compared the sensitivity of the RDTs to P. ovale malaria and Plasmodium vivax malaria.

Results: A total of 153 cases of malaria were observed, 113 of which were found among Japanese travellers. Nine patients with P. ovale malaria and 17 patients with P. vivax malaria undergoing RDTs were evaluated. The overall sensitivity of RDTs for P. ovale malaria and P. vivax malaria was 22.2% and 94.1%, respectively (P < 0.001). The sensitivity of SDMA for P. ovale malaria and P. vivax malaria was 50% and 100%, respectively. The sensitivity of BN for P. vivax malaria was 90.0%, but it was ineffective in detecting the cases of P. ovale malaria.

Conclusions: The sensitivity of RDTs was not high enough to diagnose P. ovale malaria in our study. In order not to overlook P. ovale malaria, therefore, microscopic examination is indispensable.

Detection of persistent Plasmodium spp. infections in Ugandan children after artemether-lumefantrine treatment

During a longitudinal study investigating the dynamics of malaria in Ugandan lakeshore communities, a consistently high malaria prevalence was observed in young children despite regular treatment. To explore the short-term performance of artemether-lumefantrine (AL), a pilot investigation into parasite carriage after treatment(s) was conducted in Bukoba village. A total of 163 children (aged 2–7 years) with a positive blood film and rapid antigen test were treated with AL; only 8·7% of these had elevated axillary temperatures. On day 7 and then on day 17, 40 children (26·3%) and 33 (22·3%) were positive by microscopy, respectively. Real-time PCR analysis demonstrated that multi-species Plasmodium infections were common at baseline, with 41·1% of children positive for Plasmodium falciparum/Plasmodium malariae, 9·2% for P. falciparum/ Plasmodium ovale spp. and 8·0% for all three species. Moreover, on day 17, 39·9% of children infected with falciparum malaria at baseline were again positive for the same species, and 9·2% of those infected with P. malariae at baseline were positive for P. malariae. Here, chronic multi-species malaria infections persisted in children after AL treatment(s). Better point-of-care diagnostics for non-falciparum infections are needed, as well as further investigation of AL performance in asymptomatic individuals.

Sensitivity of parasitological tests in imported Plasmodium vivax malaria in adults and impact of chemoprophylaxis and attack type

BACKGROUND

Plasmodium vivax is the second most common species among cases of imported malaria diagnosed in Europe. The objective of this study is to describe the sensitivity of the parasitological tests in imported P. vivax malaria, and the impact of chemoprophylaxis and attack type (primary infection or relapse).

METHODS

A retrospective study included the imported vivax malaria cases admitted in a French military hospital between 2001 and 2013. The reference diagnosis method was microscopy corrected by polymerase chain reaction (PCR). Thin and thick blood films examination, quantitative buffy coat (QBC) test, and a rapid diagnostic test (RDT) had been systematically performed. PCR had been carried out for ambiguous profiles.

RESULTS

Eighty-nine cases recorded from 78 patients were included, 65 of them having recently traveled to French Guyana. Forty-two patients had properly followed chemoprophylaxis. Forty-six cases were primary infections while 43 were relapses. The sensitivity was 91% for the thin blood smear, 96% for the concentration techniques (Giemsa thick blood smear and QBC test), and 76% for the RDT. The combination of the three conventional tools has an imperfect sensitivity, both for the positive diagnosis of malaria (96%) and for the diagnosis of vivax species (80%). In 4% of the cases, the positive diagnosis was established only by the PCR. The species identification was established in 20% by the PCR. The sensibility of thin blood smear and of RDT decreased significantly with full compliance of chemoprophylaxis or primary infection, whereas the decrease of sensibility of concentration techniques was not significant.

CONCLUSIONS

This study illustrates the difficulties encountered in vivax malaria diagnosis, especially in patients who properly followed chemoprophylaxis or with primary infection due to a lower parasitemia. It underlines the lack of sensitivity of RDT for P. vivax and emphasizes the need for systematically combining various diagnosis methods.

Use of qPCR and genomic sequencing to diagnose Plasmodium ovale wallikeri malaria in a returned soldier in the setting of a negative rapid diagnostic assay

Plasmodium ovale is one of several clinically relevant malaria species known to cause disease in humans. However, in contrast to Plasmodium falciparum and Plasmodium vivax, which are responsible for most cases of human malaria, P. ovale has a wide distribution but low prevalence in tropical regions. Here, we report the case of a soldier returning from Liberia with P. ovale wallikeri malaria. This case highlights the limitations of both microscopy and the malaria rapid diagnostic test for diagnosing infection with P. ovale and for distinguishing P. ovale wallikeri from P. ovale curtisi. To our knowledge, this is the first case report in which quantitative real-time polymerase chain reaction amplification using the Cytochrome B gene, coupled with genomic sequencing of the potra locus, was used for definitive diagnosis of P. ovale wallikeri malaria.