Performance of OptiMAL-IT®compared to microscopy, for malaria detection in Burkina Faso

Accuracy of rapid diagnostic test to diagnose malaria in children under 5 years of age, a meta-analysis

OBJECTIVE

To assess the accuracy of the rapid diagnostic test for malaria diagnosis in children under 5 years of age.

METHODS

As of August 31, 2020, PubMed, Web of Science and Cochrane Library databases had been systematically searched. Relevant data were extracted and meta-analysis was carried out. A random effects model was used for subgroup analysis.

RESULTS

According to the inclusion criteria, a total of 26 studies were included in this meta-analysis. The pooled sensitivity and specificity were 0.92 (95% confidence interval 0.83-0.96) and 0.92 (0.86-0.95), the parasite-specific lactate dehydrogenase-based test were 0.96 (0.85-0.98) and 0.93 (0.86-0.95), the histidine-rich protein 2-based test were 0.94 (0.84-0.98) and 0.86 (0.77-0.91).

CONCLUSIONS

This meta-analysis showed that rapid diagnostic test had good accuracy in diagnosing malaria in children under 5 years of age. And the diagnostic performance of parasite-specific lactate dehydrogenase test was better than that of the histidine-rich protein 2 test.

High value of rapid diagnostic tests to diagnose malaria within children: A systematic review and meta-analysis

Background

Children aged under five years accounted for 61% of all malaria deaths worldwide in 2017, and quicker differential diagnosis of malaria fever is vital for them. Rapid diagnostic tests (RDTs) are strips to detect

Plasmodium

specific antigens promptly and are helpful in resource-limited areas. Thus, our aim is to assess the diagnostic accuracy of RDTs for malaria in children against the gold standard.

Methods

MEDLINE, Web of Science, EMBASE, Cochrane Library, the China National Knowledge Infrastructure, Wanfang, and Sinomed databases were systematically searched on August 23, 2019. Studies that compared RDTs with microscopy or polymerase chain reaction in malaria diagnoses for children were eligible. Relevant data were extracted. The quality of studies was evaluated using the revised Quality Assessment of Diagnostic Accuracy Studies instrument. Meta-analyses were carried out to calculate the pooled estimates and 95% confidence intervals of sensitivity and specificity.

Results

51 articles were included. For diagnostic accuracy, the pooled estimates of the sensitivity and specificity of RDTs were 0.93 (95% confidence interval (CI) = 0.90, 0.95) and 0.93 (95% CI = 0.90, 0.96) respectively. Studies were highly heterogeneous, and subgroup analyses showed that the application of RDTs in high malaria transmission areas had higher sensitivity but lower specificity than those in low-to-moderate areas.

Conclusions

RDTs have high accuracy for malaria diagnosis in children, and this characteristic is more prominent in high transmission areas. As they also have the advantages of rapid-detection, are easy-to-use, and can be cost-effective, it is recommended that the wider usage of RDTs should be promoted, especially in resource-limited areas. Further research is required to assess their performance in WHO South-East Asia and Americas Region.

Genetic diversity of Plasmodium vivax and Plasmodium falciparum lactate dehydrogenases in Myanmar isolates

Background

Plasmodium lactate dehydrogenase (pLDH) is a major target in diagnosing the erythrocytic stage of malaria parasites because it is highly expressed during blood-stage parasites and is distinguished from human LDH. Rapid diagnostic tests (RDTs) for malaria use pLDH as a target antigen; however, genetic variations in pLDH within the natural population threaten the efficacy of pLDH-based RDTs.

Methods

Genetic polymorphisms of Plasmodium vivax LDH (PvLDH) and Plasmodium falciparum LDH (PfLDH) in Myanmar isolates were analysed by nucleotide sequencing analysis. Genetic polymorphisms and the natural selection of PvLDH and PfLDH were analysed using DNASTAR, MEGA6, and DnaSP ver. 5.10.00 programs. The genetic diversity and natural selection of global PvLDH and PfLDH were also analysed. The haplotype network of global PvLDH and PfLDH was constructed using NETWORK ver. 5.0.0.3. Three-dimensional structures of PvLDH and PfLDH were built with YASARA Structure ver. 18.4.24 and the impact of mutations on structural change and stability was evaluated with SDM ver. 2, CUPSAT and MAESTROweb.

Results

Forty-nine PvLDH and 52 PfLDH sequences were obtained from Myanmar P. vivax and P. falciparum isolates. Non-synonymous nucleotide substitutions resulting in amino acid changes were identified in both Myanmar PvLDH and PfLDH. Amino acid changes were also identified in the global PvLDH and PfLDH populations, but they did not produce structural alterations in either protein. Low genetic diversity was observed in global PvLDH and PfLDH, which may be maintained by a strong purifying selection.

Conclusion

This study extends knowledge for genetic diversity and natural selection of global PvLDH and PfLDH. Although amino acid changes were observed in global PvLDH and PfLDH, they did not alter the conformational structures of the proteins. These suggest that PvLDH and PfLDH are genetically well-conserved in global populations, which indicates that they are suitable antigens for diagnostic purpose and attractive targets for drug development.

Assessing the reliability of microscopy and rapid diagnostic tests in malaria diagnosis in areas with varying parasite density among older children and adult patients in Nigeria

Background:

Current malaria control strategies are based on early diagnosis and appropriate treatment of malaria cases. The study aimed at comparing the performance of blood film microscopy and rapid diagnostic test (RDT) in Plasmodium falciparum detection in patients ≥6 years of age.

Materials and Methods:

A total of 154 consecutive pyretic patients aged 6-62 years were enrolled, sampled, and tested for malaria using RDT (first response) and microscopy by Giemsa staining. Genomic DNA was extracted after saponin hemolysis and nested polymerase chain reaction (PCR) was used to detect Plasmodium falciparum. The endpoints were sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

Results:

Of the 154 patients, 80 (51.9%) had fever of ≥37.5°C. 106 (68.8%) were positive by First response^®, 132 (85.7%) by microscopy, and 121 (78.6%) by PCR. The sensitivity, specificity, PPV, and NPV of first response compared to microscopic method were 82.2%, 100.0%, 100.0%, and 34.3%, respectively, while it was 75.4%, 75.0%, 95.3%, and 31.2%, respectively, when compared to PCR. The sensitivity, specificity, PPV, and NPV of the microscopic method compared to PCR were 92.3%, 50.0%, 90.91%, and 54.5%, respectively. There was a significant difference in the performance of RDT and film microscopy methods (P ≤ 0.05).

Conclusion:

Microscopy performed better and is more reliable than first response (RDT) in areas with low parasite density among patients ≥6 years of age. Rapid diagnostic tests could be useful in aareas with high parasite density as an alternative to smear microscopy

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.

Plasmodium falciparum and Plasmodium vivax specific lactate dehydrogenase: genetic polymorphism study from Indian isolates

Control and eradication of malaria is hindered by the acquisition of drug resistance by Plasmodium species. This has necessitated a persistent search for novel drugs and more efficient targets. Plasmodium species specific lactate dehydrogenase is one of the potential therapeutic and diagnostic targets, because of its indispensable role in endoerythrocytic stage of the parasite. A target molecule that is highly conserved in the parasite population can be more effectively used in diagnostics and therapeutics, hence, in the present study polymorphism in PfLDH (Plasmodiumfalciparum specific LDH) and PvLDH (Plasmodiumvivax specific LDH) genes was analyzed using PCR-single strand confirmation polymorphism (PCR-SSCP) and sequencing. Forty-six P. falciparum and thirty-five P. vivax samples were screened from different states of India. Our findings have revealed presence of a single PfLDH genotype and six PvLDH genotypes among the studied samples. Interestingly, along with synonymous substitutions, nonsynonymous substitutions were reported to be present for the first time in the PvLDH genotypes. Further, through amino acid sequence alignment and homology modeling studies we observed that the catalytic residues were conserved in all PvLDH genotypes and the nonsynonymous substitutions have not altered the enzyme structure significantly. Evolutionary genetics studies have confirmed that PfLDH and PvLDH loci are under strong purifying selection. Phylogenetic analysis of the pLDH gene sequences revealed that P. falciparum compared to P. vivax, has recent origin. The study therefore supports PfLDH and PvLDH as suitable therapeutic and diagnostic targets as well as phylogenetic markers to understand the genealogy of malaria species.

Paracheck® rapid diagnostic test for detecting malaria infection in under five children: a population-based survey in Burkina Faso

BACKGROUND

Over the past ten years, Rapid Diagnostic Tests (RDT) played a major role in improving the use of biological malaria diagnosis, in particular in poor-resources settings. In Burkina Faso, a recent Demography and Health Survey (DHS) gave the opportunity to assess the performance of the Paracheck® test in under five children nationwide at community level.

METHODS

A national representative sample of 14,947 households was selected using a stratified two-stage cluster sampling. In one out of two households, all under five children were eligible to be tested for malaria using both RDT and microscopy diagnosis. Paracheck® performance was assessed using miscroscopy as the gold standard. Sensitivity and specificity were calculated as well as the diagnosis accuracy (DA) and the Youden index.

RESULTS

The malaria infection prevalence was estimated at 66% (95% CI: 64.8-67.2) according to microscopy and at 76.2% (95% CI: 75.1-77.3) according to Paracheck®. The sensitivity and specificity were estimated at 89.9% (95% CI: 89.0-90.8) and 50.4% (95% CI: 48.3-52.6) respectively with a Diagnosis Accuracy of 77% and a Youden index of 40%. The positive predictive value for malaria infection was 77.9% (95% CI: 76.7-79.1) and the negative predictive value was 72.1% (95% CI: 69.7-74.3). Variations were found by age group, period of the year and urban and rural areas, as well as across the 13 regions of the country.

CONCLUSION

While the sensitivity of the Paracheck® test was high, its specificity was poor in the general under five population of Burkina Faso. These results suggest that Paracheck® is not suitable to assess malaria infection prevalence at community level in areas with high malaria transmission. In such settings, malaria prevalence in the general population could be estimated using microscopy.

A novel polyclonal antibody-based sandwich ELISA for detection of Plasmodium vivax developed from two lactate dehydrogenase protein segments

BACKGROUND

Immunoassays for Plasmodium detection are, presently, most frequently based on monoclonal antibodies (MAbs); Polyclonal antibodies (PAbs), which are cheaper to develop and manufacture, are much less frequently used. In the present study we describe a sandwich ELISA assay which is capable of detecting P. vivax Lactate Dehydrogenase (LDH) in clinical blood samples, without cross reacting with those infected with P. falciparum.

METHODS

Two recombinant proteins were produced from different regions of the P. vivax LDH gene. Two sandwich ELISA assay were then designed: One which uses mouse anti-LDH 1-43aa PAbs as primary antibodies ("Test 1") and another which uses anti-LDH 35-305aa PAbs ("Test 2") as the primary antibodies. Rabbit anti-LDH 1-43aa PAbs were used as capture antibodies in both ELISA assays. Blood samples taken from P. vivax and P. falciparum infected patients (confirmed by light microscopy) were analysed using both tests.

RESULTS

"Test 2" performed better at detecting microscopy-positive blood samples when compared to "Test 1", identifying 131 of 154 positive samples (85%); 85 positives (55%) were identified using "test 1". "Test 1" produced one false positive sample (from the 20 malaria-free control) blood samples; "test 2" produced none. Kappa coefficient analysis of the results produced a value of 0.267 when microscope-positive blood smears were compared with "test 1", but 0.734 when microscope-positive blood smears were compared with the results from "test 2". Positive predictive value (PPV) and negative predictive value (NPV) were observed to be 98% and 22% respectively, for "Test 1", and 99% and 45%, for "test 2". No cross reactivity was detected with P. falciparum positive blood samples (n = 15) with either test assay.

CONCLUSION

Both tests detected P. vivax infected blood and showed no evidence of cross-reacting with P. falciparum. Further studies will need to be conducted to establish the full potential of this technique for malaria diagnostics. As well as representing a promising new cost-effective novel technique for P. vivax diagnosis and research, the method for developing this assay also highlights the potential for PAb-based strategies for diagnostics in general.

Field evaluation of rapid diagnostic tests for malaria in Yaounde, Cameroon

Rapid diagnostic tests (RDTs) are affordable, alternative diagnostic tools. The present study aimed to evaluate RDTs available in Cameroon and compare their characteristics to follow the parasitological response of patients for 28 days. Malaria diagnosis was assessed in 179 febrile patients using conventional microscopy as the reference method. Parascreen detects both Plasmodium falciparum-specific histidine-rich protein 2 (Pf HRP-2) and Pan-specific plasmodial lactate dehydrogenase (pLDH) in all four human Plasmodium spp. Diaspot is based on the detection of Pf HRP-2. OptiMAL-IT (pLDH specific for P. falciparum and pLDH for all four human Plasmodium spp.) was assessed for comparison. The reliability of RDTs was evaluated by calculating the sensitivity, specificity, positive predictive value, negative predictive value, false-positive rate, false-negative rate, and likelihood ratio. The clinical outcome of 18 children treated with atovaquone-proguanil and followed for 28 days was evaluated using microscopy and RDTs. Of 179 samples, 133 (74.3%) were pure P. falciparum-positive smears, 4 (2.2%) pure P. malariae-positive smears, and 42 (23.5%) negative smears. Parascreen and Diaspot had high sensitivity (>92%) and positive predictive values (>94%). The specificities for Parascreen and Diaspot were 81.0% and 90.5%, respectively. The false-positive rates and the false-negative rates were 19.0% and 4.5% for Parascreen and 9.5% and 8.3% for Diaspot, respectively. Most false-negatives occurred in samples with low parasitaemia (<500 asexual parasites/μL). The performance of RDTs was better at higher parasitaemia (>500 asexual parasites/μL). Four pure P. malariae were only detected by the pan-Plasmodium bands of Parascreen and OptiMAL-IT. In blood samples from patients treated and followed-up for 28 days, HRP2-based RDTs remained positive in most samples until Day 28. Despite negative smears, OptiMAL-IT remained positive in several patients until Day 7 but was negative in all patients from Day 14 onwards. RDTs can improve the management of febrile patients. The validity, ease of use, and cost of HRP2-based tests were comparable. However, one of the current weaknesses of the RDT-based strategy using the tests available in Cameroon is inadequate sensitivity for low parasitaemia. In some cases, RDT results may require correct interpretation based on clinical history, clinical examination, and microscopic diagnosis.

Accuracy of malaria rapid diagnosis test Optimal-IT(®) in Kinshasa, the Democratic Republic of Congo

Background

Despite some problems related to accuracy and applicability, malaria rapid diagnostic tests (RDTs), are currently considered the best option in areas with limited laboratory services for improving case management and reducing over-treatment. However, their performance must be established taking into the account the particularities of each endemic area. In the Democratic Republic of Congo, the validity of Optimal-IT® and Paracheck-Pf®, respectively based on the detection of lactate dehydrogenase and histidine-rich protein-2, was assessed at primary health care level (PHC).

Methods

This was a two-stage cluster randomized survey, conducted in one health centre in 12 health zones in Kinshasa city. All patients with malaria presumptive diagnosis were eligible. Gold standard was microscopy performed by experts from the parasitology unit, Kinshasa University.

Results

624 patients were enrolled. 53.4% (95% CI: 49.4-57.3) owed a bed net, obtained in 74.5% of cases (95% CI: 69.4-79.1) through community-based distribution by the National Malaria Control Programme. Microscopy expert reading confirmed 123 malaria cases (19.7%; 95% CI: 16.7-23.1). Overall sensitivity were 79.7% (95% CI: 72.4-86.8), 87.8% (95% CI: 81.9-93.6) and 86.2% (95% CI: 79.9-92.3), respectively, for Optimal-IT®, Paracheck-Pf® and microscopy performed at PHC. Specificity was 97.0% (95% CI: 95.5-98.5), 91.6% (95% CI: 89.1-94.0) and 49.1% (95% CI: 44.7-53.4). The proportion of confirmed cases seemed similar in under-fives compared to others. Any treatment prior to the current visit was a predictor for malaria (AOR: 2.3; 95% CI: 1.5-3.5), but not malaria treatment (AOR: 0.87; 95% CI: 0.4-1.8). Bed net ownership tended to protect against malaria (AOR: 0.67; 95% CI: 0.45-0.99).

Conclusion

Although microscopy is considered as the "gold standard" for malaria diagnosis at point of care level, this study showed that its accuracy may not always be satisfactory when performed in health centres.

Seasonal performance of a malaria rapid diagnosis test at community health clinics in a malaria-hyperendemic region of Burkina Faso

Backgound

Treatment of confirmed malaria patients with Artemisinin-based Combination Therapy (ACT) at remote areas is the goal of many anti-malaria programs. Introduction of effective and affordable malaria Rapid Diagnosis Test (RDT) in remote areas could be an alternative tool for malaria case management. This study aimed to assess performance of the OptiMAL dipstick for rapid malaria diagnosis in children under five.

Methods

Malaria symptomatic and asymptomatic children were recruited in a passive manner in two community clinics (CCs). Malaria diagnosis by microscopy and RDT were performed. Performance of the tests was determined.

Results

RDT showed similar ability (61.2%) to accurately diagnose malaria as microscopy (61.1%). OptiMAL showed a high level of sensitivity and specificity, compared with microscopy, during both transmission seasons (high & low), with a sensitivity of 92.9% vs. 74.9% and a specificity of 77.2% vs. 87.5%.

Conclusion

By improving the performance of the test through accurate and continuous quality control of the device in the field, OptiMAL could be suitable for use at CCs for the management and control of malaria.

Rapid diagnostic tests for diagnosing uncomplicated P. falciparum malaria in endemic countries

BACKGROUND

Rapid diagnostic tests (RDTs) for Plasmodium falciparum malaria use antibodies to detect either HRP-2 antigen or pLDH antigen, and can improve access to diagnostics in developing countries.

OBJECTIVES

To assess the diagnostic accuracy of RDTs for detecting P. falciparum parasitaemia in persons living in endemic areas who present to ambulatory healthcare facilities with symptoms suggestive of malaria by type and brand.

SEARCH STRATEGY

We undertook a comprehensive search of the following databases: Cochrane Infectious Diseases Group Specialized Register; MEDLINE; EMBASE; MEDION; Science Citation Index; Web of Knowledge; African Index Medicus; LILACS; IndMED; to January 14, 2010.

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 P. falciparum endemic areas.

DATA COLLECTION AND ANALYSIS

For each study, a standard set of data was extracted independently by two authors, using a tailored data extraction form. Comparisons were grouped hierarchically by target antigen, and type and brand of RDT, and combined in meta-analysis where appropriate.

MAIN RESULTS

We identified 74 unique studies as eligible for this review and categorized them according to the antigens they detected. Types 1 to 3 include HRP-2 (from P. falciparum) either by itself or with other antigens. Types 4 and 5 included pLDH (from P. falciparum) either by itself or with other antigens. In comparisons with microscopy, we identified 71 evaluations of Type 1 tests, eight evaluations of Type 2 tests and five evaluations of Type 3 tests. In meta-analyses, average sensitivities and specificities (95% CI) were 94.8% (93.1% to 96.1%) and 95.2% (93.2% to 96.7%) for Type 1 tests, 96.0% (94.0% to 97.3%) and 95.3% (87.3% to 98.3%) for Type 2 tests, and 99.5% (71.0% to 100.0%) and 90.6% (80.5% to 95.7%) for Type 3 tests, respectively. Overall for HRP-2, the meta-analytical average sensitivity and specificity (95% CI) were 95.0% (93.5% to 96.2%) and 95.2% (93.4% to 99.4%), respectively. For pLDH antibody-based RDTs verified with microscopy, we identified 17 evaluations of Type 4 RDTs and three evaluations of Type 5 RDTs. In meta-analyses, average sensitivity for Type 4 tests was 91.5% (84.7% to 95.3%) and average specificity was 98.7% (96.9% to 99.5%). For Type 5 tests, average sensitivity was 98.4% (95.1% to 99.5%) and average specificity was 97.5% (93.5% to 99.1%). Overall for pLDH, the meta-analytical average sensitivity and specificity (95% CI) were 93.2% (88.0% to 96.2%) and 98.5% (96.7% to 99.4%), respectively. For both categories of test, there was substantial heterogeneity in study results. Quality of the microscopy reference standard could only be assessed in 40% of studies due to inadequate reporting, but results did not seem to be influenced by the reporting quality.Overall, HRP-2 antibody-based tests (such as the Type 1 tests) tended to be more sensitive and were significantly less specific than pLDH-based tests (such as the Type 4 tests). If the point estimates for Type 1 and Type 4 tests are applied to a hypothetical cohort of 1000 patients where 30% of those presenting with symptoms have P. falciparum, Type 1 tests will miss 16 cases, and Type 4 tests will miss 26 cases. The number of people wrongly diagnosed with P. falciparum would be 34 with Type 1 tests, and nine with Type 4 tests.

AUTHORS' CONCLUSIONS

The sensitivity and specificity of all RDTs is such that they can replace or extend the access of diagnostic services for uncomplicated P. falciparum malaria. HRP-2 antibody types may be more sensitive but are less specific than pLDH antibody-based tests, but the differences are small. The HRP-2 antigen persists even after effective treatment and so is not useful for detecting treatment failures. 

Performance of rapid DiaMed OptiMal-IT(®) malaria test in an endemic Ghanaian setting

At peripheral health facility levels, the diagnosis of malaria is difficult due to lack of infrastructure. In the study reported here, the diagnostic performance of a batch of 'DiaMed OptiMAL-IT' (Cressier, Switzerland) rapid antigen tests were examined in parallel with routine microscopy for a select population of high risk individuals: 202 pregnant women and 200 children less than 5 years old in an endemic setting in Ghana. Results of both diagnostic methods were compared to that of cross-checking microscopy, taken as gold standard, at the Navrongo Health Research Centre. Of the 402 patients, 218 (54.2%) were confirmed with Plasmodium falciparum infections by cross-checking. All 218 patients (100%) were accurately diagnosed with malaria by routine microscopy. Of these, 151 (69.3%) were positive by DiaMed OptiMAL-IT test (26 false positives, 67 false negatives). DiaMed OptiMAL-IT had the following performance indicators for detection of P. falciparum among pregnant women and children less than 5 years respectively: Sensitivity-50.5% [95% CI (40.6-60.3)], 87.7% [95% CI (78.7-92.1)]; Specificity-82.5% [95% CI (73.1-89.1)], 89.6% [95% CI (80.8-94.8)]; Predictive values for positive tests-75.7% [95% CI (63.7-84.8)], 91.6% [95% CI(85.2-95.8%)]; Predictive values for negative tests-60.6% [95% CI (51.7-68.9)], 83.8% [95% CI (74.5-90.3)]; Likelihood ratio for positive tests-2.88, 10.8; Likelihood ratio for negative tests-0.59, 0.19; Cohens Kappa values-0.33 [95% CI (0.20-0.43), 0.76 [95% CI (0.65-0.83)]. Our results suggest that DiaMed OptiMAL-IT tests should not replace microscopy in our endemic setting.

Towards a precise test for malaria diagnosis in the Brazilian Amazon: comparison among field microscopy, a rapid diagnostic test, nested PCR, and a computational expert system based on artificial neural networks

Background

Accurate malaria diagnosis is mandatory for the treatment and management of severe cases. Moreover, individuals with asymptomatic malaria are not usually screened by health care facilities, which further complicates disease control efforts. The present study compared the performances of a malaria rapid diagnosis test (RDT), the thick blood smear method and nested PCR for the diagnosis of symptomatic malaria in the Brazilian Amazon. In addition, an innovative computational approach was tested for the diagnosis of asymptomatic malaria.

Methods

The study was divided in two parts. For the first part, passive case detection was performed in 311 individuals with malaria-related symptoms from a recently urbanized community in the Brazilian Amazon. A cross-sectional investigation compared the diagnostic performance of the RDT Optimal-IT, nested PCR and light microscopy. The second part of the study involved active case detection of asymptomatic malaria in 380 individuals from riverine communities in Rondônia, Brazil. The performances of microscopy, nested PCR and an expert computational system based on artificial neural networks (MalDANN) using epidemiological data were compared.

Results

Nested PCR was shown to be the gold standard for diagnosis of both symptomatic and asymptomatic malaria because it detected the major number of cases and presented the maximum specificity. Surprisingly, the RDT was superior to microscopy in the diagnosis of cases with low parasitaemia. Nevertheless, RDT could not discriminate the Plasmodium species in 12 cases of mixed infections (Plasmodium vivax + Plasmodium falciparum). Moreover, the microscopy presented low performance in the detection of asymptomatic cases (61.25% of correct diagnoses). The MalDANN system using epidemiological data was worse that the light microscopy (56% of correct diagnoses). However, when information regarding plasma levels of interleukin-10 and interferon-gamma were inputted, the MalDANN performance sensibly increased (80% correct diagnoses).

Conclusions

An RDT for malaria diagnosis may find a promising use in the Brazilian Amazon integrating a rational diagnostic approach. Despite the low performance of the MalDANN test using solely epidemiological data, an approach based on neural networks may be feasible in cases where simpler methods for discriminating individuals below and above threshold cytokine levels are available.

Nanotechnology diagnostics for infectious diseases prevalent in developing countries

Infectious diseases are prevalent in the developing world and are one of the developing world's major sources of morbidity and mortality. While infectious diseases can initiate in a localized region, they can spread rapidly at any moment due to the ease of traveling from one part of the world to the next. This could lead to a global pandemic. One key to preventing this spread is the development of diagnostics that can quickly identify the infectious agent so that one can properly treat or in some severe cases, quarantine a patient. There have been major advances in diagnostic technologies but infectious disease diagnostics are still based on 50-year technologies that are limited by speed of analysis, need for skilled workers, poor detection threshold and inability to detect multiple strains of infectious agents. Here, we describe advances in nanotechnology and microtechnology diagnostics for infectious diseases. In these diagnostic schemes, the nanomaterials are used as labels or barcodes while microfluidic systems are used to automate the sample preparation and the assays. We describe the current state of the field and the challenges.

Rapid testing for malaria in settings where microscopy is available and peripheral clinics where only presumptive treatment is available: a randomised controlled trial in Ghana

OBJECTIVE

To test in West Africa the impact of rapid diagnostic tests on the prescription of antimalarials and antibiotics both where microscopy is used for the diagnosis of malaria and in clinical (peripheral) settings that rely on clinical diagnosis.

DESIGN

Randomised, controlled, open label clinical trial.

SETTING

Four clinics in the rural Dangme West district of southern Ghana, one in which microscopy is used for diagnosis of malaria ("microscopy setting") and three where microscopy is not available and diagnosis of malaria is made on the basis of clinical symptoms ("clinical setting").

PARTICIPANTS

Patients with suspected malaria. Interventions Patients were randomly assigned to either a rapid diagnostic test or the current diagnostic method at the clinic (microscopy or clinical diagnosis). A blood sample for a research microscopy slide was taken for all patients.

MAIN OUTCOME MEASURES

The primary outcome was the prescription of antimalarials to patients of any age whose double read research slide was negative for malaria. The major secondary outcomes were the correct prescription of antimalarials, the impact of test results on antibiotic prescription, and the correct prescription of antimalarials in children under 5 years.

RESULTS

Of the 9236 patients screened, 3452 were randomised in the clinical setting and 3811 in the microscopy setting. Follow-up to 28 days was 97.6% (7088/7263). In the microscopy setting, 722 (51.6%) of the 1400 patients with negative research slides in the rapid diagnostic test arm were treated for malaria compared with 764 (55.0%) of the 1389 patients in the microscopy arm (adjusted odds ratio 0.87, 95% CI 0.71 to 1.1; P=0.16). In the clinical setting, 578 (53.9%) of the 1072 patients in the rapid diagnostic test arm with negative research slides were treated for malaria compared with 982 (90.1%) of the 1090 patients with negative slides in the clinical diagnosis arm (odds ratio 0.12, 95% CI 0.04 to 0.38; P=0.001). The use of rapid diagnostic tests led to better targeting of antimalarials and antibiotics in the clinical but not the microscopy setting, in both children and adults. There were no deaths in children under 5 years at 28 days follow-up in either arm.

CONCLUSION

Where microscopy already exists, introducing rapid diagnostic tests had limited impact on prescriber behaviour. In settings where microscopy was not available, however, using rapid diagnostic tests led to a significant reduction in the overprescription of antimalarials, without any evidence of clinical harm, and to better targeting of antibiotics. Trial registration ClinicalTrials.gov NCT00493922.

Evaluation of rapid diagnostic tests for malaria case management in Gabon

A laboratory-confirmed diagnosis is the basis of malaria case management. Rapid diagnostic tests (RDTs) create new opportunities for improved care in endemic areas. Diagnostic performance of OptiMAL-IT and Acon was assessed in comparison with microscopy at 2 sites in Gabon. Between February 2008 and January 2009, 2125 febrile children under 11 years old were diagnosed using microscopy and RDTs. Plasmodial infection was detected more frequently using Acon (27%) and OptiMAL-IT (27%) compared to microscopy (20%) (P < 0.01). Among the samples diagnosed positive by OptiMAL-IT, 78% were infected by Plasmodium falciparum, whereas 99% of positive blood smears were P. falciparum infections, 0.5% Plasmodium malariae, and 0.5% Plasmodium ovale. Both RDTs had similar sensitivity (Se) (94.0%; 95% confidence interval [CI], 92-96), which varied depending on the site. When parasite density was >100 p/microL, the Se of the 2 tests was >98% (95% CI, 96-100). Likewise, the negative predictive values were high and comparable (>98%). Overtreatment with antimalarial drugs was 12%. These tests should be considered as a good alternative to microscopy, allowing not only an efficient and rapid diagnosis of malaria in primary health facilities but also to aid in promoting changes for antimalarial prescription behavior.