Performance of PfHRP2 and PfPLDH Rapid Diagnostics Test for Diagnosis of Plasmodium falciparum in Assosa Zone, Northwest Ethiopia

Abstract Background Malaria is a life-threatening infectious disease particularly due to Plasmodium falciparum (P.falciparum ). Plasmodium falciparum Histidine-Rich Protein 2 (PfHRP-2) and Plasmodium falciparum specific Lactate Dehydrogenase (PfPLDH) based rapid diagnostic test are commonly used for malaria diagnosis in malaria endemic countries where microscopic examination is scarce. However, there is limited information on the performance of malaria RDT in rural and semi urban area of Assosa zone, Northwest Ethiopia. Thus, the aim of this study is to determine the performance of PfHRP2 and PfPLDH RDT for diagnosis of falciparum malaria against microscopy as reference method. Methods Health-facility based cross-sectional study design was conducted in Assosa zone, Northwest Ethiopia from November to December 2018. A total of four hundred and six malaria-suspected participants attending Bambasi, Sherkole, Kurmuk and Assosa health-centers were tested. Finger-prick blood samples were collected for microscopy blood film preparation, RDTs and molecular diagnosis. Statistical analyses were performed using SPSS version 20. Results Of the total study participants, 26.4% (107/406) were microscope confirmed P. falciparum positive. Using PfHRP2 and PfPLDH RDT, 30.3% (123/406) and 24.1% (98/406) were positive for P. falciparum, respectively. The sensitivity of PfHRP2 and PfPLDH was 96% and 89%, respectively, against microscope. The corresponding specificity rates of PfHRP2 and PfPLDH were 93% and 99%, respectively. Similarly, positive predictive value (PPV) and negative predictive value of PfHRP2 and PfPLDH RDT were 84%, 97%, 99% and 96%, respectively. There was an agreement between RDTs (PfPLDH and PfHRP2) and reference microscopy method with a kappa value of 0.86 and 0.90, respectively. Compared to qPCR, the specificity of PfHRP2 (93%) and PfPLDH RDT (98%) were high, though the respective sensitivity of PfHRP2(77%) and PfPLDH RDT(70%) were low. Conclusion PfHRP2 and PfPLDH showed reasonable agreement in detecting P. falciparum infections. Hence, currently used national malaria RDT kit can be continue to be used in certain malaria endemic areas in Ethiopia. However, Continuous monitoring the performance of PfHRP-2 RDT associated with false negative results is important to consider an alternative malaria RDT like PfPLDH RDT to support control and elimination of malaria in Ethiopia

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Detection of high prevalence of Plasmodium falciparum histidine-rich protein 2/3 gene deletions in Assosa zone, Ethiopia: implication for malaria diagnosis

Malaria Journal ◽

10.1186/s12936-021-03629-x ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Gezahegn Solomon Alemayehu ◽

Kayla Blackburn ◽

Karen Lopez ◽

Cheikh Cambel Dieng ◽

Eugenia Lo ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Parasite Density ◽

False Negative ◽

Malaria Diagnosis ◽

Dried Blood Spots ◽

Northwest Ethiopia ◽

Cross Sectional ◽

Gene Deletions ◽

Exon 2 ◽

Flanking Regions

Abstract Background Rapid diagnostic tests (RDTs) targeting histidine rich protein 2(HRP2) are widely used for diagnosis of Plasmodium falciparum infections. Besides PfHRP2, the PfHRP3 antigen contributes to the detection of P. falciparum infections in PfHRP2 RDTs. However, the performance HRP2-based RDT is affected by pfhrp2/3 gene deletions resulting in false-negative test results. The objective of this study was to determine the presence and prevalence of pfhrp2/3 gene deletions including the respective flanking regions among symptomatic patients in Assosa zone, Northwest Ethiopia. Methods A health-facility based cross-sectional study was conducted in febrile patients seeking a malaria diagnosis in 2018. Blood samples were collected by finger-prick for microscopic examination of blood smears, malaria RDT, and molecular analysis using dried blood spots (DBS) prepared on Whatman filter paper. A total of 218 P. falciparum positive samples confirmed by quantitative PCR were included for molecular assay of pfhrp2/3 target gene. Results Of 218 P. falciparum positive samples, exon 2 deletions were observed in 17.9% of pfhrp2 gene and in 9.2% of pfhrp3 gene. A high proportion of deletions in short segments of pfhrp2 exon1-2 (50%) was also detected while the deletions of the pfhrp3 exon1-2 gene were 4.1%. The deletions were extended to the downstream and upstream of the flanking regions in pfhrp2/3 gene (above 30%). Of eighty-six PfHRP2 RDT negative samples, thirty-six lacked pfhrp2 exon 2. Five PfHRP2 RDT negative samples had double deletions in pfhrp2 exon 2 and pfhrp3 exon2. Of these double deletions, only two of the samples with a parasite density above 2000 parasite/µl were positive by the microscopy. Three samples with intact pfhrp3 exon2 in the pfhrp2 exon2 deleted parasite isolates were found to be positive by PfHRP2 RDT and microscopy with a parasite density above 10,000/µl. Conclusion This study confirms the presence of deletions of pfhrp2/3 gene including the flanking regions. Pfhrp2/3 gene deletions results in false-negative results undoubtedly affect the current malaria control and elimination effort in the country. However, further countrywide investigations are required to determine the magnitude of pfhrp2/3 gene deletions and its consequences on routine malaria diagnosis.

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Mentorship on malaria microscopy diagnostic service in Ethiopia: Baseline competency of microscopists and performance of health facilities

10.21203/rs.3.rs-87991/v2 ◽

2021 ◽

Author(s):

Bokretsion Gidey ◽

Desalegn Nega ◽

Adugna Abera ◽

Abnet Abebe ◽

Sindew Mekasha ◽

...

Keyword(s):

Sensitivity And Specificity ◽

Predictive Value ◽

False Negative ◽

Malaria Diagnosis ◽

Health Facilities ◽

Malaria Parasites ◽

Cross Sectional ◽

Predictive Values ◽

Microscopic Diagnosis ◽

Malaria Microscopy

Abstract Background: In Ethiopia, malaria cases are declining as a result of proven interventions and in 2017, the country launched a malaria elimination strategy in targeted settings. Accurate malaria diagnosis and prompt treatment are the key components of the strategy to prevent morbidity and stop the continuation of transmission. However, the quality of microscopic diagnosis in general is deteriorating as malaria burden declines. Therefore, this study was carried out to evaluate the competency of microscopists and the performance of health facilities on malaria microscopic diagnosis.Methods: A cross-sectional study was conducted from August 1st to September 30th, 2019 in nine regional states and one city administration. A standard checklist was used for on-site evaluation, archived patient slides were re-checked, and proficiency of microscopists was tested using WHO certified slides from the national slide bank at the Ethiopian Public Health Institute (EPHI). The strength of agreement, the sensitivity, the specificity, and the positive and negative predictive values were calculated.Results: In this study, 102 health facilities (84 health centers and 18 hospitals) were included; from which, 202 laboratory professionals participated. In slide re-checking, moderate agreement (Agreement: 76.0%; Kappa: 0.41) was observed between experts and microscopists on malaria detection in all health facilities. The sensitivity and specificity of routine slide reading and the re-checking results were 78.1% and 80.7%, respectively. Likewise, positive predictive value of 65.1% and negative predictive value of 88.8% were scored in the routine diagnosis. By panel testing, a substantial overall agreement (A: 91.8%; K: 0.79) was observed between microscopists and experts in detecting malaria parasites. The sensitivity and specificity in the detection of malaria parasites was 92.7% and 89.1%, respectively. Furthermore, in identifying species, a slight agreement (A: 57%; K: 0.18) was observed between microscopists and experts. Conclusion: The study found significant false positive and false negative results in routine microscopy on slide re-checking of Plasmodium parasites. Moreover, reduced grade in parasite species identification was reported on the panel tests. Therefore, implementing comprehensive malaria microscopy mentorship, in-service training, and supportive supervision are the key strategies to improve the overall performance of health facilities in malaria microscopy.

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Mentorship on malaria microscopy diagnostic service in Ethiopia: baseline competency of microscopists and performance of health facilities

Malaria Journal ◽

10.1186/s12936-021-03655-9 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Bokretsion Gidey ◽

Desalegn Nega ◽

Adugna Abera ◽

Abnet Abebe ◽

Sindew Mekasha ◽

...

Keyword(s):

Sensitivity And Specificity ◽

Predictive Value ◽

False Negative ◽

Malaria Diagnosis ◽

Health Facilities ◽

Malaria Parasites ◽

Cross Sectional ◽

Predictive Values ◽

Microscopic Diagnosis ◽

Malaria Microscopy

Abstract Background In Ethiopia, malaria cases are declining as a result of proven interventions, and in 2017 the country launched a malaria elimination strategy in targeted settings. Accurate malaria diagnosis and prompt treatment are the key components of the strategy to prevent morbidity and stop the continuation of transmission. However, the quality of microscopic diagnosis in general is deteriorating as malaria burden declines. This study was carried out to evaluate the competency of microscopists and the performance of health facilities on malaria microscopic diagnosis. Methods A cross-sectional study was conducted from 1 August to 30 September, 2019 in 9 regional states and one city administration. A standard checklist was used for on-site evaluation, archived patient slides were re-checked and proficiency of microscopists was tested using a WHO-certified set of slides from the national slide bank at the Ethiopian Public Health Institute (EPHI). The strength of agreement, sensitivity, specificity, and positive and negative predictive values were calculated. Results In this study, 102 health facilities (84 health centres and 18 hospitals) were included, from which 202 laboratory professionals participated. In slide re-checking, moderate agreement (agreement (A): 76.0%; Kappa (K): 0.41) was observed between experts and microscopists on malaria detection in all health facilities. The sensitivity and specificity of routine slide reading and the re-checking results were 78.1 and 80.7%, respectively. Likewise, positive predictive value of 65.1% and negative predictive value of 88.8% were scored in the routine diagnosis. By panel testing, a substantial overall agreement (A: 91.8%; K: 0.79) was observed between microscopists and experts in detecting malaria parasites. The sensitivity and specificity in the detection of malaria parasites was 92.7 and 89.1%, respectively. In identifying species, a slight agreement (A: 57%; K: 0.18) was observed between microscopists and experts. Conclusion The study found significant false positive and false negative results in routine microscopy on slide re-checking of Plasmodium parasites. Moreover, reduced grade in parasite species identification was reported on the panel tests. Implementing comprehensive malaria microscopy mentorship, in-service training and supportive supervision are key strategies to improve the overall performance of health facilities in malaria microscopy.

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Investigation of HRPF2 Gene Deletion in Plasmodium Falciparum in Northwestern Nigeria

Acta Biologica Marisiensis ◽

10.2478/abmj-2021-0002 ◽

2021 ◽

Vol 4 (1) ◽

pp. 10-20

Author(s):

Dayyabu Shehu ◽

Farida Muhammad Aminu ◽

Shehu Danlami ◽

Jamila Ahmed Mashi

Keyword(s):

Plasmodium Falciparum ◽

Gene Deletion ◽

False Negative ◽

Malaria Diagnosis ◽

Housekeeping Genes ◽

Single Copy ◽

Blood Film ◽

Malaria Rapid Diagnostic Tests ◽

Thick Blood Film ◽

Strip Test

Abstract Malaria Rapid Diagnostic Tests (RDTs) plays an important role in malaria management and control. The Pf HRP2 based RDT kit is the most widely used RDT for malaria diagnosis in Nigeria but is affected by the deletion of HRP2 gene in Plasmodium falciparum parasites. Therefore, identifying the prevalence and distribution of Plasmodium falciparum parasites with deleted Pf HRP2 is important for malaria control. Pf HRP2 gene deletion was assessed in this study by first carrying out Giemsa stained thick blood film microscopy and Pf HRP2 RDT strip test. The samples were further analyzed for molecular examination by PCR assay for multiple single–copy genes (Pf Cox3, Pf HRP2, Pf HRP3 and Pf Beta tubulin). This study found the existence of eight (8) Plasmodium falciparum isolates lacking the HRP2 gene in the samples analyzed, this necessitates the need to develop a unique RDT Kit targeting other housekeeping genes unique for Plasmodium falciparum with far greater sensitivity than the current ones as to reduce the chances of false negative RDT result as well as developing unique RDT Kits targeting both PfHRP2 and PfHRP3 genes concomitantly in order to reduce the chances of having a false positive RDT results.

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Mentorship on Malaria Microscopy Diagnostic Service in Ethiopia: Baseline Competency of Microscopists and Performance of Health Facilities

10.21203/rs.3.rs-87991/v1 ◽

2020 ◽

Author(s):

Bokretsion Gidey ◽

Desalegn Nega ◽

Adugna Abera ◽

Abnet Abebe ◽

Sindew Mekasha ◽

...

Keyword(s):

Sensitivity And Specificity ◽

Predictive Value ◽

False Negative ◽

Malaria Diagnosis ◽

Cross Sectional Study ◽

Health Facilities ◽

Malaria Parasites ◽

Cross Sectional ◽

Predictive Values ◽

Malaria Microscopy

Abstract Background: In Ethiopia, malaria case is declining as a result of proven interventions and the country launched malaria elimination strategy in targeted settings since 2017. Accurate malaria diagnosis and prompt treatment are the key components of the strategy to prevent morbidity and stop continuation of the transmission. However, the quality of microscopic diagnosis in general is deteriorating as malaria burden declines. Therefore, this study was carried out toevaluate the competency of microscopists and the performance of health facilities on malaria microscopic diagnosis.Methods: A cross-sectional study was conducted from August 01 to September 30, 2019 in nine Regional States and one city administration. A standard checklist was used for on-site evaluation, archived patient slides were re-checked and proficiency of microscopists was tested using WHO certified slides from national slide bank in public health institute. Strength of agreement, sensitivity, specificity and positive and negative predictive values were calculated.Results: In this study, 102 health facilities (84 health centers and 18 hospitals) were included; from which, 202 laboratory professionals participated. In slide re-checking, moderate agreement (Agreement: 76.0%; Kappa: 0.41) was observed between experts and microscopists on malaria detection in all health facilities. The sensitivity and specificity of routine slide reading and the rechecking results were 78.1% and 80.7%, respectively. Likewise, positive predictive value of 65.1% and negative predictive value of 88.8% were scored in the routine diagnosis. By panel testing, a substantial overall agreement (A: 91.8%; K: 0.79) was observed between microscopists and experts in detecting malaria parasites. The sensitivity and specificity in detection of malaria parasites was 92.7% and 89.1%, respectively. Furthermore, in identifying species, slight agreement (A: 57%; K: 0.18) was observed between microscopists and experts. Conclusion: The study found significant false positive and false negative results in routine microscopy on slide re-checking of Plasmodium parasites. Moreover, reduced grade in parasite species identification was reported on the panel tests. Therefore, implementing comprehensive malaria microscopy mentorship, in-service training and supportive supervision are the key strategies to improve the overall performance of health facilities in malaria microscopy.

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Mentorship on malaria microscopy diagnostic service in Ethiopia: Baseline competency of microscopists and performance of health facilities

10.21203/rs.3.rs-87991/v3 ◽

2021 ◽

Author(s):

Bokretsion Gidey ◽

Desalegn Nega ◽

Adugna Abera ◽

Abnet Abebe ◽

Sindew Mekasha ◽

...

Keyword(s):

Sensitivity And Specificity ◽

Predictive Value ◽

False Negative ◽

Malaria Diagnosis ◽

Health Facilities ◽

Malaria Parasites ◽

Cross Sectional ◽

Predictive Values ◽

Microscopic Diagnosis ◽

Malaria Microscopy

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Evaluation of SD Bioline Malaria Antigen Plasmodium Falciparum / Panmalarial for Diagnosis of Malaria in Hospital Raja Permaisuri Bainun Ipoh

International Journal of Human and Health Sciences (IJHHS) ◽

10.31344/ijhhs.v0i0.165 ◽

2019 ◽

pp. 47

Author(s):

Priyaasaro Sevakumaran

Keyword(s):

Plasmodium Falciparum ◽

Predictive Value ◽

Diagnostic Tests ◽

Malaria Diagnosis ◽

Rapid Diagnostic Tests ◽

Blood Film ◽

Giemsa Staining ◽

Quality Level ◽

Malaria Antigen ◽

Supplementary Issue

Introduction: Rapid Diagnostic Tests (RDTs) for malaria has improved malaria manageme nt.Objectives: This study was conducted to evaluate the performance of SD Bioline Malaria Antigen Plasmodium falciparum/Panmalarial compared to gold standard microscopy using Giemsa staining for diagnosis of malaria in Hospital Raja Permaisuri Bainun Ipoh.Method: Microscopy and RDT diagnosis were performed on 377 blood samples. In this study, the SD Bioline Malaria Antigen Plasmodium falciparum/Panmalarial Rapid Diagnostic Tests (RDT) detecting Histidine Rich Protein II and Plasmodium lactate dehydrogenase antigens were used. Blood film malaria parasite examination was carried out as the reference.Results: Malaria parasites were identified by microscopy in 61 individuals and RDT positively tested in 27 (44.3%) patients. The sensitivity and specificity of SD Bioline Malaria Antigen Plasmodium falciparum/Panmalarial was 44.2% (95% CI, 31.8 to 57.5) and 100% (95% CI, 98.6 to 100.0) respectively. The positive predictive value (PPV) for SD Bioline Malaria Antigen Plasmodium falciparum/Panmalarial was 100% (95% CI, 84.5 to 100) and the negative predictive value (NPV) was 90% (95% CI, 86.6 to 93.1).Discussion: The SD Bioline Malaria Antigen Plasmodium falciparum/ Panmalarial test showed excellent results in the diagnosis of endemic Plasmodium falciparum infections. This SD Bioline Antigen Plasmodium falciparum/ Panmalarial loses validity for low parasitemia. These results confirm the validity of SD Bioline Antigen Plasmodium falciparum/ Panmalarial in malaria diagnosis must be complemented by microscopy.Conclusion: This examination has demonstrated that the SD Bioline Malaria Antigen Plasmodium falciparum/ Panmalarial cannot be utilized as an elective strategy contrasted with the best quality level Giemsa staining (BFMP). These outcomes affirm that whenever supplemented by microscopy, SD Bioline Malaria Antigen Plasmodium falciparum/ Panmalarial are substantial in malaria analysis.International Journal of Human and Health Sciences Supplementary Issue: 2019 Page: 47

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Community-based surveys for Plasmodium falciparum pfhrp2 and pfhrp3 gene deletions in selected regions of mainland Tanzania

Malaria Journal ◽

10.1186/s12936-020-03459-3 ◽

2020 ◽

Vol 19 (1) ◽

Author(s):

Catherine Bakari ◽

Sophie Jones ◽

Gireesh Subramaniam ◽

Celine I. Mandara ◽

Mercy G. Chiduo ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Single Gene ◽

False Negative ◽

Malaria Diagnosis ◽

Positive Control ◽

Cross Sectional Survey ◽

Community Based ◽

Cross Sectional ◽

Gene Deletions ◽

Antigen Assay

Abstract Background Histidine-rich protein 2 (HRP2)-based malaria rapid diagnostic tests (RDTs) are effective and widely used for the detection of wild-type Plasmodium falciparum infections. Although recent studies have reported false negative HRP2 RDT results due to pfhrp2 and pfhrp3 gene deletions in different countries, there is a paucity of data on the deletions of these genes in Tanzania. Methods A community-based cross-sectional survey was conducted between July and November 2017 in four regions: Geita, Kigoma, Mtwara and Ruvuma. All participants had microscopy and RDT performed in the field and provided a blood sample for laboratory multiplex antigen detection (for Plasmodium lactate dehydrogenase, aldolase, and P. falciparum HRP2). Samples showing RDT false negativity or aberrant relationship of HRP2 to pan-Plasmodium antigens were genotyped to detect the presence/absence of pfhrp2/3 genes. Results Of all samples screened by the multiplex antigen assay (n = 7543), 2417 (32.0%) were positive for any Plasmodium antigens while 5126 (68.0%) were negative for all antigens. The vast majority of the antigen positive samples contained HRP2 (2411, 99.8%), but 6 (0.2%) had only pLDH and/or aldolase without HRP2. Overall, 13 samples had an atypical relationship between a pan-Plasmodium antigen and HRP2, but were positive by PCR. An additional 16 samples with negative HRP2 RDT results but P. falciparum positive by microscopy were also chosen for pfhrp2/3 genotyping. The summation of false negative RDT results and laboratory antigen results provided 35 total samples with confirmed P. falciparum DNA for pfhrp2/3 genotyping. Of the 35 samples, 4 (11.4%) failed to consistently amplify positive control genes; pfmsp1 and pfmsp2 and were excluded from the analysis. The pfhrp2 and pfhrp3 genes were successfully amplified in the remaining 31 (88.6%) samples, confirming an absence of deletions in these genes. Conclusions This study provides evidence that P. falciparum parasites in the study area have no deletions of both pfhrp2 and pfhrp3 genes. Although single gene deletions could have been missed by the multiplex antigen assay, the findings support the continued use of HRP2-based RDTs in Tanzania for routine malaria diagnosis. There is a need for the surveillance to monitor the status of pfhrp2 and/or pfhrp3 deletions in the future.

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No evidence of false-negative Plasmodium falciparum rapid diagnostic results in Monrovia, Liberia

Malaria Journal ◽

10.1186/s12936-021-03774-3 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Mandella King ◽

Alexander E. George ◽

Pau Cisteró ◽

Christine K. Tarr-Attia ◽

Beatriz Arregui ◽

...

Keyword(s):

Plasmodium Falciparum ◽

False Negative ◽

Malaria Diagnosis ◽

Rapid Diagnostic Tests ◽

Molecular Testing ◽

False Negatives ◽

Gene Deletions ◽

History Of ◽

Catholic Hospital ◽

Or History

Abstract Background Malaria diagnosis in many malaria-endemic countries relies mainly on the use of rapid diagnostic tests (RDTs). The majority of commercial RDTs used in Africa detect the Plasmodium falciparum histidine-rich protein 2 (PfHRP2). pfhrp2/3 gene deletions can therefore lead to false-negative RDT results. This study aimed to evaluate the frequency of PCR-confirmed, false-negative P. falciparum RDT results in Monrovia, Liberia. Methods PfHRP2-based RDT (Paracheck Pf®) and microscopy results from 1038 individuals with fever or history of fever (n = 951) and pregnant women at first antenatal care (ANC) visit (n = 87) enrolled in the Saint Joseph’s Catholic Hospital (Monrovia) from March to July 2019 were used to assess the frequency of false-negative RDT results. True–false negatives were confirmed by detecting the presence of P. falciparum DNA by quantitative PCR in samples from individuals with discrepant RDT and microscopy results. Samples that were positive by 18S rRNA qPCR but negative by PfHRP2-RDT were subjected to multiplex qPCR assay for detection of pfhrp2 and pfhrp3. Results One-hundred and eighty-six (19.6%) and 200 (21.0%) of the 951 febrile participants had a P. falciparum-positive result by RDT and microscopy, respectively. Positivity rate increased with age and the reporting of joint pain, chills and shivers, vomiting and weakness, and decreased with the presence of coughs and nausea. The positivity rate at first ANC visit was 5.7% (n = 5) and 8% (n = 7) by RDT and microscopy, respectively. Out of 207 Plasmodium infections detected by microscopy, 22 (11%) were negative by RDT. qPCR confirmed absence of P. falciparum DNA in the 16 RDT-negative but microscopy-positive samples which were available for molecular testing. Among the 14 samples that were positive by qPCR but negative by RDT and microscopy, 3 only amplified pfldh, and among these 3 all were positive for pfhrp2 and pfhrp3. Conclusion There is no qPCR-confirmed evidence of false-negative RDT results due to pfhrp2/pfhrp3 deletions in this study conducted in Monrovia (Liberia). This indicates that these deletions are not expected to affect the performance of PfHRP2-based RDTs for the diagnosis of malaria in Liberia. Nevertheless, active surveillance for the emergence of PfHRP2 deletions is required.

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The epidemiology and detectability of asymptomatic Plasmodium vivax and Plasmodium falciparum infections in low, moderate and high transmission settings in Ethiopia

Malaria Journal ◽

10.1186/s12936-021-03587-4 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Elifaged Hailemeskel ◽

Surafel K Tebeje ◽

Sinknesh W. Behaksra ◽

Girma Shumie ◽

Getasew Shitaye ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Plasmodium Vivax ◽

Age Groups ◽

Diagnostic Tools ◽

Asymptomatic Malaria ◽

Rapid Diagnostics ◽

Cross Sectional ◽

Low Transmission ◽

High Transmission ◽

Study Sites

Abstract Background As countries move to malaria elimination, detecting and targeting asymptomatic malaria infections might be needed. Here, the epidemiology and detectability of asymptomatic Plasmodium falciparum and Plasmodium vivax infections were investigated in different transmission settings in Ethiopia. Method: A total of 1093 dried blood spot (DBS) samples were collected from afebrile and apparently healthy individuals across ten study sites in Ethiopia from 2016 to 2020. Of these, 862 were from community and 231 from school based cross-sectional surveys. Malaria infection status was determined by microscopy or rapid diagnostics tests (RDT) and 18S rRNA-based nested PCR (nPCR). The annual parasite index (API) was used to classify endemicity as low (API > 0 and < 5), moderate (API ≥ 5 and < 100) and high transmission (API ≥ 100) and detectability of infections was assessed in these settings. Results In community surveys, the overall prevalence of asymptomatic Plasmodium infections by microscopy/RDT, nPCR and all methods combined was 12.2% (105/860), 21.6% (183/846) and 24.1% (208/862), respectively. The proportion of nPCR positive infections that was detectable by microscopy/RDT was 48.7% (73/150) for P. falciparum and 4.6% (2/44) for P. vivax. Compared to low transmission settings, the likelihood of detecting infections by microscopy/RDT was increased in moderate (Adjusted odds ratio [AOR]: 3.4; 95% confidence interval [95% CI] 1.6–7.2, P = 0.002) and high endemic settings (AOR = 5.1; 95% CI 2.6–9.9, P < 0.001). After adjustment for site and correlation between observations from the same survey, the likelihood of detecting asymptomatic infections by microscopy/RDT (AOR per year increase = 0.95, 95% CI 0.9–1.0, P = 0.013) declined with age. Conclusions Conventional diagnostics missed nearly half of the asymptomatic Plasmodium reservoir detected by nPCR. The detectability of infections was particularly low in older age groups and low transmission settings. These findings highlight the need for sensitive diagnostic tools to detect the entire parasite reservoir and potential infection transmitters.

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