Sensitivity Of Rapid Diagnostic Tests Research Articles

Evaluation of serological tests in the diagnosis of scrub typhus

Scrub typhus is a leading cause of acute undifferentiated febrile illness in India. Overlapping clinical presentation and very low incidence of characteristic eschar makes serology the main stay of diagnosis. IgM ELISA is the most common test performed in tertiary care centres along with rapid diagnostic tests (RDT) and Weil Felix with varying sensitivity and specificityThe present study was conducted to compare the RDT’s and Weil Felix with IgM ELISA and analyse the demographic and clinical profile of scrub positive patientsSerum samples from clinically suspected scrub typhus patients admitted in a tertiary care hospital were tested by Weil Felix, RDT and IgM ELISA. Scrub typhus was confirmed in 38 of the 100 clinically suspected patients by IgM ELISA. Fever was the most common presenting symptom with significant proportion of patients being exposed to vegetation (p=0.0001).Sensitivity of Weil Felix and RDT was 42.1% and 84.2% respectively. Acute Kidney injury was the most common complication and mortality rate was 7.9%.Weil Felix is not a reliable test for scrub typhus diagnosis due to low sensitivity. Results of positive RDT’s can used for early initiation of specific treatment and IgM ELISA can be used as a confirmatory test in highly suspected cases.

A measles IgM rapid diagnostic test to address challenges with national measles surveillance and response in Malaysia.

A lateral flow rapid diagnostic test (RDT) enables detection of measles specific immunoglobulin M (IgM) antibody in serum, capillary blood, and oral fluid with accuracy consistent with enzyme immunoassay (EIA). The objectives of the study were: 1) to assess measles RDT inter-reader agreement between two clinic staff; 2) to assess the sensitivity and specificity of the measles RDT relative to standard surveillance testing in a low transmission setting; 3) to evaluate the knowledge, attitudes, and practices of staff in clinics using the RDT; and 4) to assess the impact of RDT testing on the measles public health response in Malaysia. The clinic-based prospective evaluation included all suspected measles cases captured by routine measles surveillance at 34 purposely selected clinics in 15 health districts in Malaysia between September 2019 and June 2020, following day-long regional trainings on RDT use. Following informed consent, four specimens were collected from each suspected case, including those routinely collected for standard surveillance [serum for EIA and throat swabs for quantitative reverse transcriptase polymerase chain reaction (RT-qPCR)] together with capillary blood and oral fluid tested with RDTs during the study. RDT impact was evaluated by comparing the rapidity of measles public health response between the pre-RDT implementation (December 2018 to August 2019) and RDT implementation periods (September 2019 to June 2020). To assess knowledge, attitudes, and practices of RDT use, staff involved in the public health management of measles at the selected sites were surveyed. Among the 436 suspect cases, agreement of direct visual readings of measles RDT devices between two health clinic staff was 99% for capillary blood (k = 0.94) and 97% for oral fluid (k = 0.90) specimens. Of the total, 45 (10%) were positive by measles IgM EIA (n = 44, including five also positive by RT-qPCR) or RT-qPCR only (n = 1), and 38 were positive by RDT (using either capillary blood or oral fluid). Using measles IgM EIA or RT-qPCR as reference, RDT sensitivity using capillary blood was 43% (95% CI: 30%-58%) and specificity was 98% (95% CI: 96%-99%); using oral fluid, sensitivity (26%, 95% CI: 15%-40%) and specificity (97%, 95% CI: 94%-98%) were lower. Nine months after training, RDT knowledge was high among staff involved with the public health management of measles (average quiz score of 80%) and was highest among those who received formal training (88%), followed by those trained during supervisory visits (83%). During the RDT implementation period, the number of days from case confirmation until initiation of public response decreased by about 5 days. The measles IgM RDT shows >95% inter-reader agreement, high retention of RDT knowledge, and a more rapid public health response. However, despite ≥95% RDT specificity using capillary blood or oral fluid, RDT sensitivity was <45%. Higher-powered studies using highly specific IgM assays and systematic RT-qPCR for case confirmation are needed to establish the role of RDT in measles elimination settings.

Lesson Learned from Mass Antibody Rapid Diagnostic Used in the Early COVID-19 Pandemic in Indonesia Contributors.

Laboratory examination is extremely important in handling the COVID-19 pandemic. In the first era of the pandemic, the molecular and antigen tests were limited. Hence, at that time, it was necessary to carry out antibody Rapid Diagnostic Tests (RDT). However, many antibody RDTs were yet to obtain Food and Drug Authorization (FDA)'s approval. Therefore, The Indonesian Association of Clinical Pathology and Medical Laboratory (PDS PatKLIn) decided to conduct a validity test of RDT antibodies to find out the quality of SARS-CoV-2 diagnosis performance based on these RDTs used. This is a descriptive observational design with diagnostic analysis. The retrospective secondary data were collected from 34 provinces in Indonesia from May to June 2020. Data analysis was carried out on the sensitivity and specificity values of each antibody RDT brand to the RT-PCR result and analyzed descriptive data. The amount of secondary data of antibody RDT and RT-PCR results collected was 139,908, consisting of 59 RDT brands of which 44% were authorized by The Indonesian COVID-19 Response Acceleration Task Force (Gugus Tugas Percepatan Penanganan COVID-19 Indonesia). There were huge variations of SARS-CoV-2 antibody RDT performance between total antibody types (sensitivity 59.18%, specificity 62%), IgM RDT (sensitivity 16-100%, specificity 7-97%), and RDT IgG (sensitivity 33-96%, specificity 19-100%). The variations in the RDT antibodies'performance can cause errors in diagnosis leading to significant material and immaterial losses. Therefore, cooperation from various parties is needed for the pre- and post-marketing surveillance process to assess the performance and the characteristics of each RDT kit and other diagnostic methods to assist the rapid pandemic response process.

Comparative Diagnostic Performance of Microscopy, SD-Bioline Rapid Diagnostic Test, and Polymerase Chain Reaction in the Detection of Malaria Infection among Pregnant Women at Delivery in Kumba Health District Area in the Southwest Region of Cameroon

Introduction. Malaria during pregnancy is a major cause of morbidity and mortality in sub-Saharan Africa. Microcopy and rapid diagnostic test (RDT) recommended by the World Health Organization for clinical diagnosis have poor sensitivity to detect individuals with very low levels of parasitemia. Previous studies have shown that malaria in pregnancy is associated with mastitis and excessive uterine blood loss during delivery. However, information evaluating the performance of these tools in detecting malaria in pregnancy at the national level is limited. This study therefore evaluates the performance of microscopy, RDT, and nested polymerase chain reaction (nPCR) in the detection of pregnancy-associated malaria at delivery. Methods. A total of 227 participants constituting of 201 pregnant women without and 26 with HIV were recruited from five health facilities within the Kumba health district area. Mother venous and cord blood were collected at delivery to test for malaria using the thick-film microscopy, SD-bioline RDT, and 18SrRNA-nested PCR. Results. The percentage of malaria-positive cases detected by thick-film microcopy (TFM), RDT, and PCR in pregnant women with and without HIV was 7.69%, 53.85%, and 50% and 3.48%, 23.38%, and 49.25%, respectively. Plasmodium falciparum was detected in 1.99% cord blood samples of women without HIV by PCR. The positivity rate in at least two of the test methods (composite positive) was 42.31% for women with and 19.90% for women without HIV. The sensitivity of TFM and RDT when using PCR as a reference was 7.21% and 49.00%, respectively, in all samples. The specificity was 99.14% and 90.55% with kappa values of 0.064 and 0.461, respectively. When using the composite test as a reference, the sensitivity of TFM, RDT, and nPCR was 15.69%, 94.12%, and 100%, respectively. Specificity was 99.43%, 93.18%, and 65.34% with kappa values of 0.213, 0.821, and 0.458, respectively. Conclusion. This study shows that PCR is more sensitive in the detection of malaria parasite followed by SD-bioline RDT kit. However, in resource-limited settings where access to molecular diagnosis of malaria is a problem, RDT should be considered as the first option to microscopy in the diagnosis of malaria.

Sensitivity and specificity of a syphilis rapid diagnostic test in blood donors’ samples

Rapid Diagnostic Tests (RDT) are useful to identify syphilis cases, particularly for hard-to-reach populations and if laboratory services are scarce. However, RDT performance may be suboptimal. We aimed to assess the sensitivity and specificity of a syphilis RDT using well-characterized blood donors’ samples. We categorized samples from 811 blood donors into five groups: 1 - Samples with reactive Chemiluminescence (QML), FTA-Abs, and VDRL; 2 - Samples with reactive QML and FTA-Abs, and nonreactive VDRL; 3 - Samples with reactive QML, and nonreactive for other markers (false-positives); 4 - Controls with nonreactive QML; and 5 - Samples reactive for HIV, with nonreactive QML. Sensitivity was tested in groups 1 (overall and according to VDRL titers) and 2; specificity was tested in groups 3‒5. The RDT had high specificity, even in samples reactive for HIV. The sensitivity was high (91.9%) in samples with reactive VDRL but varied between 75.0%‒100% according to VDRL titers. The overall sensitivity was lower (81.3%) in samples with reactive FTA-Abs and nonreactive VDRL. The RDT is a useful tool to detect active syphilis but may be more limited for cases with very early or remote infection, or those with prior treatment. When higher sensitivity is needed, additional strategies including recurrent testing or laboratory-based tests may be required.

Diagnostic value of rapid test for malaria among febrile neonates in a tertiary hospital in North-East Nigeria: a prospective cross-sectional study

ObjectiveThe WHO recommends testing using microscopy or rapid diagnostic test (RDT) before treatment for malaria. However, the use of RDT to diagnose neonatal malaria has not been widely validated with...

Performance of ultra-sensitive malaria rapid diagnostic test to detect Plasmodium falciparum infection in pregnant women in Kinshasa, the Democratic Republic of the Congo

BackgroundLow peripheral parasitaemia caused by sequestration of Plasmodium falciparum in the placenta hampers the diagnosis of malaria in pregnant women, leading to microscopy or conventional rapid diagnostic tests (RDTs) false-negative results. Although mainly asymptomatic, maternal malaria remains harmful to pregnant women and their offspring in endemic settings and must be adequately diagnosed. Ultra-sensitive RDTs (uRDTs) are thought to be more sensitive than RDTs, and their diagnostic performance was assessed in the current study in pregnant women living in Kinshasa, a stable malaria transmission area in the Democratic Republic of the Congo.MethodsTo assess and compare the diagnostic performances of both RDTs and uRDTs, 497 peripheral blood samples were tested using microscopy and quantitative polymerase chain reaction (qPCR) as the index and the reference tests, respectively. The agreement between the different diagnostic tests assessed was estimated by Cohen's Kappa test.ResultsThe median parasite density by qPCR was 292 p/μL of blood [IQR (49.7–1137)]. Using qPCR as the reference diagnostic test, the sensitivities of microscopy, RDT and uRDT were respectively [55.7% (95% CI 47.6–63.6)], [81.7% (95%CI 74.7–87.3)] and [88% (95% CI 81.9–92.6)]. The specificities of the tests were calculated at 98.5% (95% CI 96.6–99.5), 95.2% (95% CI 92.5–97.2) and 94.4% (95% CI 91.4–96.6) for microscopy, RDT and uRDT, respectively. The agreement between qPCR and uRDT was almost perfect (Kappa = 0.82). For parasite density (qPCR) below 100 p/µL, the sensitivity of RDT was 62% (95% CI 47.1–75.3) compared to 68% (95% CI 53.3–80.4) for uRDT. Between 100 and 200 p/µL, the sensitivity of RDT was higher, but still lower compared to uRDT: 89.4% (95% CI 66.8–98.7) for RDT versus 100% (95% CI 82.3–100) for uRDT. In both cases, microscopy was lower, with 20% (95% CI 10–33.7) and 47.3% (95% CI 24.4–71.1) respectively.ConclusionsuRDT has the potential to improve malaria management in pregnant women as it has been found to be slightly more sensitive than RDT in the detection of malaria in pregnant women but the difference was not significant. Microscopy has a more limited value for the diagnosis of malaria during the pregnancy, because of its lower sensitivity.

Cost-effectiveness of incorporating Ebola prediction score tools and rapid diagnostic tests into a screening algorithm: A decision analytic model.

No distinctive clinical signs of Ebola virus disease (EVD) have prompted the development of rapid screening tools or called for a new approach to screening suspected Ebola cases. New screening approaches require evidence of clinical benefit and economic efficiency. As of now, no evidence or defined algorithm exists. To evaluate, from a healthcare perspective, the efficiency of incorporating Ebola prediction scores and rapid diagnostic tests into the EVD screening algorithm during an outbreak. We collected data on rapid diagnostic tests (RDTs) and prediction scores' accuracy measurements, e.g., sensitivity and specificity, and the cost of case management and RDT screening in EVD suspect cases. The overall cost of healthcare services (PPE, procedure time, and standard-of-care (SOC) costs) per suspected patient and diagnostic confirmation of EVD were calculated. We also collected the EVD prevalence among suspects from the literature. We created an analytical decision model to assess the efficiency of eight screening strategies: 1) Screening suspect cases with the WHO case definition for Ebola suspects, 2) Screening suspect cases with the ECPS at -3 points of cut-off, 3) Screening suspect cases with the ECPS as a joint test, 4) Screening suspect cases with the ECPS as a conditional test, 5) Screening suspect cases with the WHO case definition, then QuickNavi™-Ebola RDT, 6) Screening suspect cases with the ECPS at -3 points of cut-off and QuickNavi™-Ebola RDT, 7) Screening suspect cases with the ECPS as a conditional test and QuickNavi™-Ebola RDT, and 8) Screening suspect cases with the ECPS as a joint test and QuickNavi™-Ebola RDT. We performed a cost-effectiveness analysis to identify an algorithm that minimizes the cost per patient correctly classified. We performed a one-way and probabilistic sensitivity analysis to test the robustness of our findings. Our analysis found dual ECPS as a conditional test with the QuickNavi™-Ebola RDT algorithm to be the most cost-effective screening algorithm for EVD, with an effectiveness of 0.86. The cost-effectiveness ratio was 106.7 USD per patient correctly classified. The following algorithms, the ECPS as a conditional test with an effectiveness of 0.80 and an efficiency of 111.5 USD per patient correctly classified and the ECPS as a joint test with the QuickNavi™-Ebola RDT algorithm with an effectiveness of 0.81 and a cost-effectiveness ratio of 131.5 USD per patient correctly classified. These findings were sensitive to variations in the prevalence of EVD in suspected population and the sensitivity of the QuickNavi™-Ebola RDT. Findings from this study showed that prediction scores and RDT could improve Ebola screening. The use of the ECPS as a conditional test algorithm and the dual ECPS as a conditional test and then the QuickNavi™-Ebola RDT algorithm are the best screening choices because they are more efficient and lower the number of confirmation tests and overall care costs during an EBOV epidemic.

Seroprevalence of HIV, Hepatitis B and C Viruses, and Treponema Pallidum among Blood Donors Attending the Garoua Regional Hospital Blood Bank, North Cameroon, a Cross-Sectional Study

Background. Human immunodeficiency virus (HIV), hepatitis B (HBV), and hepatitis C virus (HCV) are transfusion-transmittable infections (TTI). They currently constitute a major public health problem in Cameroon, like in other developing countries. Little is known about the seroprevalence of HIV, HBV, HCV, and syphilis among blood donors in northern region Cameroun. This study aims at filling the gap on the unknown sero-prevalence of those markers in blood donors. Methods. We conducted a cross-sectional study from June 04, to July 08, 2022 at the Garoua Regional Hospital Blood Bank (GRHBB). A total of 201donors were consecutively included and data on donor’s sociodemographic characteristics were obtained by the national program’s questionnaire. Serum samples from blood donors were tested using sensitive third generation Rapid diagnostic test (RDT) for presence of Hepatits B surface antigens (HBsAg), and antibodies to human immunodeficiency (HIV-1/2), Hepatits C (HCV) and Treponema pallidum; and quantitative enzyme-linked immunosorbent assays (ELISA) served for confirmation. Data were collected and entered into an Excel sheet and then exported to SPSS version 20.0 for analysis. Results. A total of 201 blood donors were identified and the sex ratio (male/female) was 7/1, with a mean age of 32.12 ± 8.4 years (range: 19 to 57 years). Of all blood donors, 35/201 (17.4%) were infested by at least one of the four TTIs. Among blood donors, HIV, HBV, HCV and syphilis were 5 (2.5%); 26 (12.9%); 1 (0.5%) and 5 (2.5%), respectively. Co-infection with HIV-Syphilis was 1 (0.5%); and HBV-HCV 1 (0.5%). Conclusions. This study has revealed the high prevalence of TTIs in blood donors who attended the Garoua Regional Hospital Blood Bank, identifying Hepatitis B as the greatest threat to blood safety in the North Region of Cameroon.

Spatial Clustering and Risk Factors for Malaria Infections and Marker of Recent Exposure to Plasmodium falciparum from a Household Survey in Artibonite, Haiti.

Targeting malaria interventions in elimination settings where transmission is heterogeneous is essential to ensure the efficient use of resources. Identifying the most important risk factors among persons experiencing a range of exposure can facilitate such targeting. A cross-sectional household survey was conducted in Artibonite, Haiti, to identify and characterize spatial clustering of malaria infections. Household members (N = 21,813) from 6,962 households were surveyed and tested for malaria. An infection was defined as testing positive for Plasmodium falciparum by either a conventional or novel highly sensitive rapid diagnostic test. Seropositivity to the early transcribed membrane protein 5 antigen 1 represented recent exposure to P. falciparum. Clusters were identified using SaTScan. Associations among individual, household, and environmental risk factors for malaria, recent exposure, and living in spatial clusters of these outcomes were evaluated. Malaria infection was detected in 161 individuals (median age: 15 years). Weighted malaria prevalence was low (0.56%; 95% CI: 0.45-0.70%). Serological evidence of recent exposure was detected in 1,134 individuals. Bed net use, household wealth, and elevation were protective, whereas being febrile, over age 5 years, and living in either households with rudimentary wall material or farther from the road increased the odds of malaria. Two predominant overlapping spatial clusters of infection and recent exposure were identified. Individual, household, and environmental risk factors are associated with the odds of individual risk and recent exposure in Artibonite; spatial clusters are primarily associated with household-level risk factors. Findings from serology testing can further strengthen the targeting of interventions.

A Diagnostic Accuracy Study to Evaluate Standard Rapid Diagnostic Test (RDT) Alone to Safely Rule Out Imported Malaria in Children Presenting to UK Emergency Departments.

Microscopy is the gold standard for malaria diagnosis but is dependent on trained personnel. Rapid diagnostic tests (RDTs) form the mainstay of diagnosis in endemic areas without access to high-quality microscopy. We aimed to evaluate whether RDT alone could rule out imported malaria in children presenting to UK emergency departments (EDs). UK-based, multi-center, retrospective, diagnostic accuracy study. Included: any child <16 years presenting to ED with history of fever and travel to a malaria-endemic country, between 01/01/2016 and 31/12/2017. Diagnosis: microscopy for malarial parasites (clinical reference standard) and RDT (index test). UK Health Research Authority approval: 20/HRA/1341. There were 47 cases of malaria out of 1,414 eligible cases (prevalence 3.3%) in a cohort of children whose median age was 4 years (IQR 2-9), of whom 43% were female. Cases of Plasmodium falciparum totaled 36 (77%, prevalence 2.5%). The sensitivity of RDT alone to detect malaria infection due to any Plasmodium species was 93.6% (95% CI 82.5-98.7%), specificity 99.4% (95% CI 98.9-99.7%), positive predictive value 84.6% (95% CI 71.9-93.1%) and negative predictive value 99.8% (95% CI 99.4-100.0%). Sensitivity of RDT to detect P. falciparum infection was 100% (90.3-100%), specificity 98.8% (98.1-99.3%), positive predictive value 69.2% (54.9-81.2%, n = 46/52) and negative predictive value 100% (99.7-100%, n = 1,362/1,362). RDTs were 100% sensitive in detecting P. falciparum malaria. However, lower sensitivity for other malaria species and the rise of pfhrp2 and pfhrp3 (pfhrp2/3) gene deletions in the P. falciparum parasite mandate the continued use of microscopy for diagnosing malaria.

Laboratory Evaluation and Field Testing of Dengue NS1 and IgM/IgG Rapid Diagnostic Tests in an Epidemic Context in Senegal.

In Senegal, the burden of dengue is increasing and expanding. As case management and traditional diagnostic techniques can be difficult to implement, rapid diagnostic tests (RDTs) deployed at point of care are ideal for investigating active outbreaks. The aim of this study was to evaluate the diagnostic performance of the Dengue NS1 and Dengue IgM/IgG RDTs on the serum/plasma samples in a laboratory setting and in the field. During laboratory evaluation, performance of the NS1 RDT was assessed using NS1 ELISA as the gold standard. Sensitivity and specificity were 88% [75-95%] and 100% [97-100%], respectively. Performance of the IgM/IG RDT was assessed using the IgM Antibody Capture (MAC) ELISA, indirect IgG, and PRNT as gold standards. The IgM and IgG test lines respectively displayed sensitivities of 94% [83-99%] and 70% [59-79%] and specificities of 91% [84-95%] and 91% [79-98%]. In the field, the Dengue NS1 RDT sensitivity and specificity was 82% [60-95%] and 75% [53-90%], respectively. The IgM and IgG test lines displayed sensitivities of 86% [42-100%] and 78% [64-88%], specificities of 85% [76-92%] and 55% [36-73%], respectively. These results demonstrate that RDTs are ideal for use in a context of high prevalence or outbreak setting and can be implemented in the absence of a confirmatory test for acute and convalescent patients.

Evaluation of ten (10) SARS-CoV-2 rapid serological tests in comparison with WANTAI SARS-CoV-2 ab ELISA in Burkina Faso, West Africa

BackgroundThe aim of this study was to evaluate the performance of ten (10) SARS-CoV-2 serological rapid diagnostic tests in comparison with the WANTAI SARS-CoV-2 Ab ELISA test in a laboratory setting.Materials and methodsTen (10) SARS-CoV-2 serological rapid diagnostic tests (RDTs) for SARS-CoV-2 IgG/IgM were evaluated with two (2) groups of plasma tested positive for one and negative for the other with the WANTAI SARS-CoV-2 Ab ELISA. The diagnostic performance of the SARS-CoV-2 serological RDTs and their agreement with the reference test were calculated with their 95% confidence intervals.ResultsThe sensitivity of serological RDTs ranged from 27.39 to 61.67% and the specificity from 93.33 to 100% compared to WANTAI SARS-CoV-2 Ab ELISA test. Of all the tests, two tests (STANDARD Q COVID-19 IgM/IgG Combo SD BIOSENSOR and COVID-19 IgG/IgM Rapid Test (Zhejiang Orient Gene Biotech Co., Ltd)) had a sensitivity greater than 50%. In addition, all ten tests had specificity greater than or equal to 93.33% each. The concordance between RDTs and WANTAI SARS-CoV-2 Ab ELISA test ranged from 0.25 to 0.61.ConclusionThe SARS-CoV-2 serological RDTs evaluated show low and variable sensitivities compared to the WANTAI SARS-CoV-2 Ab ELISA test, with however a good specificity. These finding may have implications for the interpretation and comparison of COVID-19 seroprevalence studies depending on the type of test used.

Diagnostic performance of NxTek™ Eliminate Malaria-Pf test for the detection of Plasmodium falciparum in school children with asymptomatic malaria

BackgroundOne of the major roadblocks to the falciparum malaria elimination programme is the presence of a portion of the population, such as school children, with asymptomatic malaria infection. Targeting such reservoirs of infections is critical to interrupting transmission and enhancing elimination efforts. The NxTek™ Eliminate Malaria Pf test is a highly sensitive rapid diagnostic test (hsRDT) for the detection of HRP-2. However, knowledge gaps exist in Ethiopia on the diagnostic performance of hsRDT for the detection of Plasmodium falciparum in school children with asymptomatic malaria.MethodsA school-based cross-sectional study was conducted from September 2021 to January 2022 on 994 healthy school children (aged 6–15 years). Finger-pricked whole blood samples were collected for microscopy, hsRDT, conventional RDT (cRDT or SD Bioline Malaria Ag Pf/P.v), and QuantStudio™ 3 Real—Time PCR system (qPCR). The hsRDT was compared to cRDT and microscopy. qPCR and microscopy were used as reference methods.ResultsThe prevalence of Plasmodium falciparum was 1.51%, 2.2%. 2.2% and 4.52%, by microscopy, hsRDT, cRDT and qPCR, respectively. Using qPCR as reference, the sensitivity of hsRDT was higher (48.89%) than the microscopy (33.3%), and showed 100% specificity and a positive predictive value (PPV). Microscopy showed similar specificity and PPV as hsRDT. Using microscopy as a reference, the diagnostic perforrmances of both hsRDT and cRDT were similar. Both RDTs demonstrated identical diagnostic performances in both comparison methods.ConclusionshsRDT has the same diagnostic performance as cRDT but improved diagnostic characteristics than microscopy for detection of P. falciparum in school children with asymptomatic malaria. It can be a useful tool for the national malaria elimination plan of Ethiopia.

Comparison between the Diagnostic Performances of Rapid Diagnostic Test (RDT) using Advantage Malaria Card Pf/Pv Ag, Microscopy, and Polymerase Chain Reaction (PCR) in Malaria Suspected patients at the Merauke Regional General Hospital

Malaria prevalence in Indonesia is still high, especially in eastern Indonesia, namely Papua, reaching a peak of 16%, for example, in Merauke. The diagnosis of Malaria is conducted according to the gold standard, using the microscopy method. However, it is still limited, raising the need for a Rapid Diagnostic Test (RDT) examination. This study aims to evaluate the diagnostic performances of Immunochromatography (ICT) based RDT (using Advantage Malaria Card Pf/Pv Ag), compared to the diagnostic performances of microscopy and Polymerase Chain Reaction (PCR).This cross-sectional observational study took all fever patients of outpatient and inpatient care at the Merauke Regional General Hospital (hereinafter referred to as RSUD Merauke) from June to July 2019 as the samples. The sample population included all malaria patients with positive microscopy results, and the control population included all non-malarial fever patients at RSUD Merauke. Each specimen underwent microscopy (thick and thin preparations), RDT, and Real-Time (RT)-PCR tests using a Rotor Gene-Q (Qiagen) with abTESTM malaria 5qPCR III reagent. The diagnostic performances of RDT were analyzed by calculating its sensitivity, specificity, Positive Predictive Value (PPV), and Negative Predictive Value (NPV). The study was conducted on 105 samples, namely 55 malaria samples and 50 control samples, who underwent microscopy, RDT, and RT-PCR. RDT sensitivity to microscopy, P. vivax 100%, P. falciparum 89.5%; specificity of P. vivax 95.7%, P. falciparum 97.7%. RDT sensitivity to RT-PCR, P. vivax 53.5%, P. falciparum 48.6%; specificity of P. vivax 100%, P. falciparum 98.5%. The RDT p-value for microscopy and RT-PCR was p=0.000. RDT k-coefficient of microscopy, P. vivax 0.937, P. falciparum 0.871. RDT k-coefficient of PCR, P. vivax 0.427, P. falciparum 0.531. RDT is more sensitive to P. vivax than microscopy. RDT is more specific to P. vivax than RT-PCR. Further studies are suggested to discuss anti-malaria drug resistance and sequencing.

Portable and cost-effective genetic detection and characterization of Plasmodium falciparum hrp2 using the MinION sequencer

The prevalence of Plasmodium falciparum hrp2 (pfhrp2)-deleted parasites threatens the efficacy of the most used and sensitive malaria rapid diagnostic tests and highlights the need for continued surveillance for this gene deletion. While PCR methods are adequate for determining pfhrp2 presence or absence, they offer a limited view of its genetic diversity. Here, we present a portable sequencing method using the MinION. Pfhrp2 amplicons were generated from individual samples, barcoded, and pooled for sequencing. To overcome potential crosstalk between barcodes, we implemented a coverage-based threshold for pfhrp2 deletion confirmation. Amino acid repeat types were then counted and visualized with custom Python scripts following de novo assembly. We evaluated this assay using well-characterized reference strains and 152 field isolates with and without pfhrp2 deletions, of which 38 were also sequenced on the PacBio platform to provide a standard for comparison. Of 152 field samples, 93 surpassed the positivity threshold, and of those samples, 62/93 had a dominant pfhrp2 repeat type. PacBio-sequenced samples with a dominant repeat-type profile from the MinION sequencing data matched the PacBio profile. This field-deployable assay can be used alone for surveilling pfhrp2 diversity or as a sequencing-based addition to the World Health Organization’s existing deletion surveillance protocol.

Prevalence of histidine-rich protein 2 deletion among the Plasmodium falciparum isolates from Kolkata.

Histidine-rich protein 2 (HRP2) detecting rapid diagnostic tests (RDTs) have played an important role in enabling prompt malaria diagnosis in remote locations. HRP2 has advantages over other biomarkers because of its abundance in the bloodstream, repetitive binding epitopes, and falciparum-specificity. Most HRP2-based RDTs also exhibit some cross-reactivity to a closely related protein (HRP3). Plasmodium falciparum parasites lacking HRP2 (pfhrp2) and 3 (pfhrp3) genes escape detection by these RDTs. The objective of the study was to study the sensitivity and specificity of hrp2-based RDT for diagnosis of falciparum, to compare the RDT results with microscopy and polymerase chain reaction (PCR), and to determine the prevalence of HRP2 gene deletion among the RDT-negative, microscopy-positive falciparum strains. Blood samples were collected and diagnosis was done by microscopic examination, RDTs, and PCR. Out of 1000 patients examined, 138 were positive for P. falciparum. Fever was the most common symptom followed by chills with rigor and headache were recorded among more than >95% of the study patients. Three microscopy-confirmed P. falciparum cases were negative by HRP2-based RDT and were found to have deletion of HRP2 and HRP3 exon 2. Rapid and accurate diagnosis and prompt deployment of effective antimalarial medication are essential components of appropriate case management. P. falciparum strains that evade diagnosis by RDTs represent a major threat to malaria control and elimination efforts.

Microscopic and submicroscopic infection by Plasmodium falciparum: Immunoglobulin M and A profiles as markers of intensity and exposure.

Assessment of serological Plasmodium falciparum–specific antibodies in highly endemic areas provides valuable information about malaria status and parasite exposure in the population. Although serological evidence of Plasmodium exposure is commonly determined by Plasmodium-specific immunoglobulin G (IgG) levels; IgM and IgA are likely markers of malaria status that remain relatively unexplored. Previous studies on IgM and IgA responses have been based on their affinity for single antigens with shortage of immune responses analysis against the whole Plasmodium proteome. Here, we provide evidence of how P. falciparum infection triggers the production of specific IgM and IgA in plasma and its relationship with parasite density and changes in hematological parameters. A total of 201 individuals attending a hospital in Breman Asikuma, Ghana, were recruited into this study. Total and P. falciparum–specific IgM, IgA, and IgG were assessed by ELISA and examined in relation to age (0–5, 14–49, and ≥50 age ranges); infection (submicroscopic vs. microscopic malaria); pregnancy and hematological parameters. Well-known IgG response was used as baseline control. P. falciparum–specific IgM and IgA levels increased in the population with the age, similarly to IgG. These data confirm that acquired humoral immunity develops by repeated infections through the years endorsing IgM and IgA as exposure markers in endemic malaria regions. High levels of specific IgA and IgM in children were associated with microscopic malaria and worse prognosis, because most of them showed severe anemia. This new finding shows that IgM and IgA may be used as diagnostic markers in this age group. We also found an extremely high prevalence of submicroscopic malaria (46.27% on average) accompanied by IgM and IgA levels indistinguishable from those of uninfected individuals. These data, together with the observed lack of sensitivity of rapid diagnostic tests (RDTs) compared to PCR, invoke the urgent need to implement diagnostic markers for submicroscopic malaria. Overall, this study opens the potential use of P. falciparum–specific IgM and IgA as new serological markers to predict malaria status in children and parasite exposure in endemic populations. The difficulties in finding markers of submicroscopic malaria are highlighted, emphasizing the need to explore this field in depth.

Virus variant–specific clinical performance of SARS coronavirus two rapid antigen tests in point-of-care use, from November 2020 to January 2022

ObjectivesAntigen rapid diagnostic tests (RDTs) for SARS coronavirus 2 (SARS-CoV-2) are quick, widely available, and inexpensive. Consequently, RDTs have been established as an alternative and additional diagnostic strategy to quantitative reverse transcription polymerase chain reaction (RT-qPCR). However, reliable clinical and large-scale performance data specific to a SARS-CoV-2 virus variant of concern (VOC) are limited, especially for the Omicron VOC. The aim of this study was to compare RDT performance among different VOCs. MethodsThis single-centre prospective performance assessment compared RDTs from three manufacturers (NADAL, Panbio, MEDsan) with RT-qPCR including deduced standardized viral load from oropharyngeal swabs for detection of SARS-CoV-2 in a clinical point-of-care setting from November 2020 to January 2022. ResultsAmong 35 479 RDT/RT-qPCR tandems taken from 26 940 individuals, 164 of the 426 SARS-CoV-2 positive samples tested true positive with an RDT corresponding to an RDT sensitivity of 38.50% (95% CI, 34.00–43.20%), with an overall specificity of 99.67% (95% CI, 99.60–99.72%). RDT sensitivity depended on viral load, with decreasing sensitivity accompanied by descending viral load. VOC-dependent sensitivity assessment showed a sensitivity of 42.86% (95% CI, 32.82–53.52%) for the wild-type SARS-CoV-2, 43.42% (95% CI, 32.86–54.61%) for the Alpha VOC, 37.67% (95% CI, 30.22–45.75%) for the Delta VOC, and 33.67% (95% CI, 25.09–43.49%) for the Omicron VOC. Sensitivity in samples with high viral loads of ≥106 SARS-CoV-2 RNA copies per mL was significantly lower in the Omicron VOC (50.00%; 95% CI, 36.12–63.88%) than in the wild-type SARS-CoV-2 (79.31%; 95% CI, 61.61–90.15%; p 0.015). DiscussionRDT sensitivity for detection of the Omicron VOC is reduced in individuals infected with a high viral load, which curtails the effectiveness of RDTs. This aspect furthert: limits the use of RDTs, although RDTs are still an irreplaceable diagnostic tool for rapid, economic point-of-care and extensive SARS-CoV-2 screening.

Comparison of Two Different Serological Viral Marker Testing Assays for Screening of Apheresis Donors: Which Assay Provides Optimum Safety for Transfusion?

While whole blood testing has evolved over the years, viral marker testing for plateletpheresis donors is still performed by Rapid Diagnostic Tests (RDT). Aim of this study was to compare diagnostic accuracy of RDT and Chemiluminescence Immunoassay (CLIA) in serological testing for HBsAg, anti-HCV and anti-HIV antibodies. A prospective, analytical study was conducted in the department of Transfusion Medicine at a tertiary healthcare center in India between September 2016 and August 2018. Samples were simultaneously tested by CLIA, RDT and a confirmatory test. Sensitivity, specificity, negative and positive predictive values and mean time taken to report results were calculated. A total of 102 (1.48%) of the 6883 samples were found to be reactive by either or both the assays. A total of 74 (1.08%) samples were HBsAg reactive, 23 (0.33%) were reactive for anti-HCV antibodies and 5 (0.07%) were reactive for anti-HIV I and II antibodies. A combined sero-prevalence of 1.05% (72) was observed; 0.78% (54) for HBsAg, 0.26% (18) for anti-HCV antibodies and none for anti-HIV I and II antibodies. Four (3.85%) reactive samples were missed by RDT and therefore sensitivity of RDT was quite less as compared to CLIA. RDT and CLIA both were found to have a statistically significant shorter turnaround time than confirmatory tests. There is increasing need to develop a safe donor screening strategy for plateletpheresis. CLIA offers an excellent alterative to RDT for viral marker testing in terms of sensitivity.