Evaluation of Two Malaria Rapid Diagnostic Tests Quality Assurance (mRDT’s QA) Methods in Peripheral Health Facilities, Rural Tanzania.

\ud WHO recommends confirming suspected malaria cases before initiation of treatment. Due to the imited availability of quality microscopy services, this recommendation has been followed with increased use of antigen-detecting malaria rapid diagnostic tests (mRDTs) in many malaria endemic countries. With the increased use of mRDTs, the need for a thorough mRDT quality assurance (RDT QA) method has become more apparent. One of the WHO recommendations for RDT QA is to monitor the tests in field use monthly, by comparing mRDT results to reference microscopy. This study was carried out to monitor mRDT performance in selected health facilities using two quality assurance methods; first based on ference microscopy and second based on detection of parasite DNA by real time quantitative PCR (qPCR) on dried blood spots (DBS); as well as assessing the cost and timeliness of the two QA methods. Blood samples were collected from patients undergoing a rapid test for malaria for two to three consecutive days per month, for five months, in 12 health facilities in Iringa rural and Mufindi districts. The health workers were instructed to label RDT cassettes, blood smear slides, and filter papers for DBS with matching unique ID stickers. A sticker was also placed in the log book where RDT results were recorded. Blood smears (BS) were first read at the district hospital (BS1) and then transported to Bagamoyo for a reference reading at the IHI- Bagamoyo laboratory (BS2). A third BS reader (BS3) was consulted from Muhimbili University of Health and Allied Sciences (MUHAS) in case of discordant results between BS1 and BS2. Molecular analysis involved extraction of parasite DNA from DBS samples using a QIAamp DNA Mini Kit. Sample DNA aliquots were compared against standard solutions with parasite DNA diluted 10-fold to give a parasitemia ranging from 200,000/μL to 20/μL. About 20% of the study DNA aliquots were sent to the CDC laboratory in Atlanta in order to validate qPCR results performed at the Bagamoyo laboratory. Data were entered in Microsoft Access (Microsoft Corporation, 2006) and analyzed in STATA 10 (StataCorp, Texas USA). Because of the known limitations of mRDTs to detect parasitemia below 200 parasites/μL, BS and PCR results greater than or equal to 5 parasites/200 WBC or 200 parasites/μL were considered positive in comparisons with mRDT performance. In the univariate analysis, proportions of positive tests were compared among the three types of tests: mRDT, microscopy and qPCR. Microscopy readings were categorized into 3 groups; BS1, BS2 and /or BS summary which is an average of BS1 and BS2. In case of discordant results between BS1 and BS2, a third reader- BS3 was consulted. Chi-squared test was done to assess differences in proportion of positive tests per district; whereas McNemar’s test was Malaria RDT QA Final Report, March 2012 5 used to assess the difference in test positivity by type of test. Kappa statistic was used to quantify the strength of the agreement between tests results. In addition, we examined health workers performance of the testing procedure when attending patients at a health facility, using a predefined checklist. Towards the end of the study, an evaluation of health worker acceptability was carried out to assess preferences between the two RDT QA methods. We received 2369 samples and 2324 (98%) had complete information. mRDTs had the highest positivity rate (6.5%). The proportion of positive tests by all types of tests was slightly higher in Iringa DC, but only qPCR and BS2 showed statistically significant differences in positivity rate between the two districts, where Iringa DC had more positive tests than Mufindi DC (p<0.05). When qPCR was a gold standard, mRDTs had higher sensitivity (68.6%, 95%CI: 55.0-79.7) than microscopy (53.7%, 95%CI: 38.7- 68.0) but highest mRDT sensitivity was achieved with comparison to microscopy (85.3%, 95%CI: 70.0- 93.6). All tests had higher inter-observer agreement than would be expected by chance. Substantial high inter-observer agreement (kappa =0.75; p<0.001) was seen amongst the microscopists i.e. district’s quality assurance officers and the reference microscopy readings. Assessment of the time needed to process BS at the district level revealed that, smears at district level took on average 8 days (min 2 to max 33) to be processed and provide feedback; but up to an average of 44 days (min 19 to max 98) to get a second reading. Many health workers were aware that the use of mRDTs was due to changes in treatment policy (11/30), and patients who qualify for the test are those suspected to have malaria. Majority (16/30) related assessment of control line as a measure of test accuracy and suggested the use of microscopy for quality control of mRDT results (15/30). Their major concerns were mRDTs’ inability to give parasite count, stock-out of the tests kits in their working areas and the frequency of negative results. This evaluation encountered several challenges, among them were 1. Poor quality of blood smears made at health facilities, especially dispensaries, which do not have laboratory services. 2. About 3.5% of BS1 slides could not be processed for BS2 because they were damaged during transportation and/or poor quality of smears. This accounts for the small difference in the numbers of BS assessed between two readers. 3. We were not able to prepare standard concentration solutions for qPCR analysis in the country. 4. Problems with PCR machine and inability to repair it that necessitated shipment of the machine, to and from, the manufacturers in Europe (Germany). Malaria RDT QA Final Report, March 2012 6 Due to these challenges, qPCR results were not available until after specimen collection had ended. In this study malaria positivity was higher with mRDTs than microscopy and qPCR for the 200 parasites/μL lower boundary of positivity threshold. This could either be due to the strict lower cut-off point for microscopy and qPCR parasite density or higher false positivity of mRDTs due to persistent antigen in blood, errors in mRDTs performance or other patient’s characteristics. When qPCR was taken as gold standard, mRDTs showed better sensitivity than microscopy, but when microscopy was regarded as a gold standard, mRDTs showed higher sensitivity than with qPCR. However, results of qPCR demonstrated a better correlation (inter-observer agreement) with those of microscopy than with mRDTs. The challenges of performing qPCR, as observed in this evaluation, make it unsuitable for quality assurance of mRDTs in routine care, Tanzania. The high inter-observer agreement between districts’ and reference microscopists (K=0.75) and higher tests performances of BS1 when BS2 was a comparator, demonstrates the competence shown by district’s technicians/ technologists to suffice their involvement as reference microscopists for quality assurance of mRDTs in their respective districts. This is also complimented by a fact that, both BS1 and BS2 had more similar performance when qPCR was taken as a gold standard. In this setting, a microscopy-based quality assurance system to assess mRDT performance in routine use may be a practical and suitable method. However, long distance transportation of smears should be avoided.\u

Immunologic activation of human syncytiotrophoblast by Plasmodium falciparum

<p>Abstract</p> <p>Background</p> <p>Malaria during pregnancy is characterized by the sequestration of malaria-infected red blood cells (iRBC) in the intervillous spaces of the placenta, often accompanied by the infiltration of maternal mononuclear cells, causing substantial maternal and foetal/infant morbidity. The iRBC bind to receptors expressed by the syncytiotrophoblast (ST). How ST responds to this interaction remains poorly understood. Because it is known that ST is immunoactive and can respond to infectious agents, the consequences of this ST-iRBC interaction should be investigated.</p> <p>Methods</p> <p>An in vitro system was used to assess the biochemical and immunological changes induced in ST by ST-adherent iRBCs. Changes in ST mitogen-activated protein kinase (MAPK) activation were assessed by immunoblotting and mRNA expression levels of selected cytokine and chemokines in primary ST bound by iRBC were determined using real-time, reverse transcription PCR. In addition, secreted cytokine and chemokine proteins were assayed by standard ELISA, and chemotaxis of PBMC was assessed using a two-chamber assay system.</p> <p>Results</p> <p>Following iRBC/ST interaction, ST C-Jun N-terminal kinase 1 (JNK1) was activated and modest increases in the mRNA expression of TGF-β and IL-8/CXCL8 were observed. In addition, this interaction increased secretion of MIF and MIP-1α/CCL3 by ST and induced migration of PBMC towards iRBC-stimulated ST.</p> <p>Conclusion</p> <p>Results from this study provide the first evidence that ST participates in shaping the local immunological milieu and in the recruitment of maternal immune cells to the maternal blood space during placental malaria infection.</p

Field Evaluation of the Photo-induced Electron Transfer Fluorogenic Primers (PET) Real-time PCR for the Detection of Plasmodium falciparum in Tanzania.

Accurate diagnosis of malaria infections remains challenging, especially in the identification of submicroscopic infections. New molecular diagnostic tools that are inexpensive, sensitive enough to detect low-level infections and suitable in laboratory settings of resource-limited countries are required for malaria control and elimination programmes. Here the diagnostic potential of a recently developed photo-induced electron transfer fluorogenic primer (PET) real-time polymerase chain reaction (PCR) called PET-PCR was investigated. This study aimed to (i) evaluate the use of this assay as a method for the detection of both Plasmodium falciparum and other Plasmodium species infections in a developing country's diagnostic laboratory; and, (ii) determine the assay's sensitivity and specificity compared to a nested 18S rRNA PCR. Samples used in this study were obtained from a previous study conducted in the region of Iringa, Tanzania. A total of 303 samples from eight health facilities in Tanzania were utilized for this evaluation. All samples were screened using the multiplex PET-PCR assay designed to detect Plasmodium genus and P. falciparum initially in laboratory in Tanzania and then repeated at a reference laboratory at the CDC in the USA. Microscopy data was available for all the 303 samples. A subset of the samples were tested in a blinded fashion to find the sensitivity and specificity of the PET-PCR compared to the nested 18S rRNA PCR. Compared to microscopy, the PET-PCR assay was 59% more sensitive in detecting P. falciparum infections. The observed sensitivity and specificity were 100% (95% confidence interval (CI0.95) = 94-100%) and (CI0.95 = 96-100%), respectively, for the PET-PCR assay when compared to nested 18S rRNA PCR. When compared to 18S rRNA PCR, microscopy had a low sensitivity of 40% (CI0.95 = 23-61%) and specificity of 100% (CI0.95 = 96-100%). The PET-PCR results performed in the field laboratory in Tanzania were in 100% concordance with the results obtained at the reference laboratory in the USA. The PET-PCR is a new molecular diagnostic tool with similar performance characteristics as commonly used PCR methods that is less expensive, easy to use, and amiable to large scale-surveillance studies in developing country settings

Plasma levels of angiopoietin-1 and -2 predict cerebral malaria outcome in Central India

<p>Abstract</p> <p>Background</p> <p>The mechanisms underlying the pathogenesis of cerebral malaria (CM) syndrome are not well understood. Previous studies have shown a strong association of inflammatory chemokines, apoptotic markers and angiogenic molecules with CM associated mortality. Recognizing the importance of angiopoietins (ANG) in the pathogenesis of CM, a retrospective investigation was carried out in a hospital cohort of malaria patients with <it>Plasmodium </it>infection in central India to determine if these factors could be suitable markers of CM associated severity.</p> <p>Methods</p> <p>Patients enrolled in the study were clinically characterized as healthy controls (HC), mild malaria (MM), CM survivors (CMS) and CM non-survivors (CMNS) based on their malaria status and hospital treatment outcome. Plasma ANG-1 and ANG-2 levels were assessed using sandwich ELISA. Receiver operating characteristic (ROC) curve analysis was used to calculate area under the curve (AUC) for each biomarker in order to assess predictive accuracy of individual biomarkers.</p> <p>Results</p> <p>The plasma levels of ANG-1 were lower in CMS and CMNS compared to control groups (mild malaria and healthy controls) at the time of hospital admission. On the contrary, ANG-2 levels positively correlated with malaria severity and were significantly higher in CMNS. The ratio of ANG-2/ANG-1 was highest in CMNS compared to other groups. Receiver operating characteristic curves revealed that compared to ANG-1 (AUC = 0.35), ANG-2 (AUC = 0.95) and ratio of ANG-2/ANG-1 (AUC = 0.90) were better markers to discriminate CMNS from MM cases. However, they were less specific in predicting fatal outcome amongst CM cases at the time of hospital admission.</p> <p>Conclusion</p> <p>These results suggest that at the time of admission plasma levels of ANG-2 and ratio of ANG-2/ANG-1 are clinically informative biomarkers to predict fatal CM from MM cases while they have limited usefulness in discriminating fatal CM outcomes in a pool of CM cases in endemic settings of Central India.</p

Antibody responses to the merozoite surface protein-1 complex in cerebral malaria patients in India

<p>Abstract</p> <p>Background</p> <p><it>Plasmodium falciparum </it>infection causes cerebral malaria (CM) in a subset of patients with anti-malarial treatment protecting only about 70% to 80% of patients. Why a subset of malaria patients develops CM complications, including neurological sequelae or death, is still not well understood. It is believed that host immune factors may modulate CM outcomes and there is substantial evidence that cellular immune factors, such as cytokines, play an important role in this process. In this study, the potential relationship between the antibody responses to the merozoite surface protein (MSP)-1 complex (which consists of four fragments namely: MSP-1₈₃, MSP-1₃₀, MSP-1₃₈and MSP-1₄₂), MSP-6₃₆and MSP-7₂₂and CM was investigated.</p> <p>Methods</p> <p>Peripheral blood antibody responses to recombinant antigens of the two major allelic forms of MSP-1 complex, MSP-6₃₆and MSP-7₂₂were compared between healthy subjects, mild malaria patients (MM) and CM patients residing in a malaria endemic region of central India. Total IgG and IgG subclass antibody responses were determined using ELISA method.</p> <p>Results</p> <p>The prevalence and levels of IgG and its subclasses in the plasma varied for each antigen. In general, the prevalence of total IgG, IgG1 and IgG3 was higher in the MM patients and lower in CM patients compared to healthy controls. Significantly lower levels of total IgG antibodies to the MSP-1_f38, IgG1 levels to MSP-1_d83, MSP-1₁₉and MSP-6₃₆and IgG3 levels to MSP-1_f42and MSP-7₂₂were observed in CM patients as compared to MM patients.</p> <p>Conclusion</p> <p>These results suggest that there may be some dysregulation in the generation of antibody responses to some MSP antigens in CM patients and it is worth investigating further whether perturbations of antibody responses in CM patients contribute to pathogenesis.</p

Defining the next generation of Plasmodium vivax diagnostic tests for control and elimination: Target product profiles.

The global prevalence of malaria has decreased over the past fifteen years, but similar gains have not been realized against Plasmodium vivax because this species is less responsive to conventional malaria control interventions aimed principally at P. falciparum. Approximately half of all malaria cases outside of Africa are caused by P. vivax. This species places dormant forms in human liver that cause repeated clinical attacks without involving another mosquito bite. The diagnosis of acute patent P. vivax malaria relies primarily on light microscopy. Specific rapid diagnostic tests exist but typically perform relatively poorly compared to those for P. falciparum. Better diagnostic tests are needed for P. vivax. To guide their development, FIND, in collaboration with P. vivax experts, identified the specific diagnostic needs associated with this species and defined a series of three distinct target product profiles, each aimed at a particular diagnostic application: (i) point-of-care of acutely ill patients for clinical care purposes; (ii) point-of-care asymptomatic and otherwise sub-patent residents for public health purposes, e.g., mass screen and treat campaigns; and (iii) ultra-sensitive not point-of-care diagnosis for epidemiological research/surveillance purposes. This report presents and discusses the rationale for these P. vivax-specific diagnostic target product profiles. These contribute to the rational development of fit-for-purpose diagnostic tests suitable for the clinical management, control and elimination of P. vivax malaria

Diagnostic performance of loop-mediated isothermal amplification and ultra-sensitive rapid diagnostic tests for malaria screening among pregnant women in Kenya

Background: Screen-and-treat strategies with sensitive diagnostic tests may reduce malaria-associated adverse pregnancy outcomes. We conducted a diagnostic accuracy study to evaluate new point-of-care tests to screen pregnant women for malaria at their first antenatal visit in western Kenya. Methods: Consecutively women were tested for Plasmodium infection by expert-microscopy, conventional rapid diagnostic test (cRDT), ultra-sensitive RDT (usRDT), and loop-mediated isothermal amplification (LAMP). Photo-induced electron-transfer polymerase-chain-reaction (PET-PCR) served as the reference standard. Diagnostic performance was calculated and modelled at low parasite densities. Results: Between May-September 2018, 172 out of 482 screened participants (35.7%) were PET-PCR positive. Relative to PET-PCR, expert-microscopy was least sensitive (40.1%, 95% CI 32.7-47.9), followed by cRDT (49.4%, 41.7-57.1), usRDT (54.7%, 46.9-62.2), and LAMP (68.6%, 61.1-75.5). Test sensitivities were comparable in febrile women (N=90). Among afebrile women (N=392), the geometric- mean parasite density was 29 parasites/μL and LAMP (sensitivity=61.9%) and usRDT (43.2%) detected 1.74 (1.31-2.30) and 1.21 (0.88-2.21) more infections than cRDT (35.6%). Per our model, tests performed similarly at densities >200 parasites/μL. At 50 parasites/μL, the sensitivities were 45%, 56%, 62% and 74% with expert-microscopy, cRDT, usRDT, and LAMP, respectively. Conclusions: This first-generation usRDT provided moderate improvement in detecting low-density infections in afebrile pregnant women compared to cRDTs

Real-Time Fluorescence Loop Mediated Isothermal Amplification for the Diagnosis of Malaria

BACKGROUND: Molecular diagnostic methods can complement existing tools to improve the diagnosis of malaria. However, they require good laboratory infrastructure thereby restricting their use to reference laboratories and research studies. Therefore, adopting molecular tools for routine use in malaria endemic countries will require simpler molecular platforms. The recently developed loop-mediated isothermal amplification (LAMP) method is relatively simple and can be improved for better use in endemic countries. In this study, we attempted to improve this method for malaria diagnosis by using a simple and portable device capable of performing both the amplification and detection (by fluorescence) of LAMP in one platform. We refer to this as the RealAmp method. METHODOLOGY AND SIGNIFICANT FINDINGS: Published genus-specific primers were used to test the utility of this method. DNA derived from different species of malaria parasites was used for the initial characterization. Clinical samples of P. falciparum were used to determine the sensitivity and specificity of this system compared to microscopy and a nested PCR method. Additionally, directly boiled parasite preparations were compared with a conventional DNA isolation method. The RealAmp method was found to be simple and allowed real-time detection of DNA amplification. The time to amplification varied but was generally less than 60 minutes. All human-infecting Plasmodium species were detected. The sensitivity and specificity of RealAmp in detecting P. falciparum was 96.7% and 91.7% respectively, compared to microscopy and 98.9% and 100% respectively, compared to a standard nested PCR method. In addition, this method consistently detected P. falciparum from directly boiled blood samples. CONCLUSION: This RealAmp method has great potential as a field usable molecular tool for diagnosis of malaria. This tool can provide an alternative to conventional PCR based diagnostic methods for field use in clinical and operational programs