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M'Bondoukwé NP, Owono-Medang M, Moussavou-Boussougou MN, Akoue Y, Migueba V, Bulaev D, Neven A, James LAJ, Ntsame Ella SA, Mawili-Mboumba DP, Atsame J, Vaillant M, Bouyou Akotet MK. Low diagnostic performance of thick blood smears of 50 µl in comparison with direct examination of 10 µl blood and the leukoconcentration technique of 5ml blood among loiasis-suspected patients with low microfilaremia in Gabon, Central Africa, using the STARD-BLCM guidelines. Parasit Vectors 2024; 17:138. [PMID: 38491557 PMCID: PMC10943916 DOI: 10.1186/s13071-023-06089-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 12/08/2023] [Indexed: 03/18/2024] Open
Abstract
BACKGROUND The aim of this study was to determine performance indicators of thick blood smears of 50 µl (TBS-50), following the Standards for the Reporting of Diagnostic Accuracy Studies-Bayesian Latent Class Model (STARD-BLCM) guidelines. TBS-50 was compared with two common parasitological techniques-direct examination of 10 µl blood and a leukoconcentration of 5 ml-for the diagnosis of microfilaremic loiasis. METHODS The study population was recruited among patients of the Department of Parasitology-Mycology-Tropical Medicine over a period of 1 year. Age, sex, symptoms, and eosinophilia variables were recorded from laboratory registers and medical files. Direct examination of 10 µl of blood, TBS-50, and the leukoconcentration technique with 5 ml of blood were performed for each patient. The classical formula and BLCM were used to determine the diagnostic accuracy of the three techniques as well as the prevalence of microfilaremic loiasis. Three models were built within the framework of BLCM-the BLCM model I and alternative models II and III-for sensitivity analysis. RESULTS In total, 191 patients consented to be included. The direct blood examination and TBS-50 yielded comparable qualitative and quantitative results. Hence, they are reported together. The prevalence of Loa loa microfilaremia was 9.4% (95% CI 5.7-14.5; n = 18/191) with direct blood examination/TBS-50 and 12.6% [8.2-18.1] (n = 24/191) for leukoconcentration. Comparing TBS-50 with the leukoconcentration method using the classical formula, the sensitivity was 75.0% [53.3-90.2], specificity was 100.0% [97.8-100.0], the positive predictive value was 100.0% [81.5-100.0], and the negative predictive value was 96.5% [92.6-98.7]. The prevalence of microfilaremic loiasis was estimated at 9.7% [6.2-13.7] using BLCM model I. The outputs of BLCM model I showed sensitivity of 78.9% [65.3-90.3], specificity of 100.0% [99.3-100.0], a positive predictive value of 99.1% [87.2-100.0], and a negative predictive value of 93.0% [87.3-97.7] for direct blood examination/TBS-50. CONCLUSIONS TBS-50 demonstrates low sensitivity relative to two other techniques. In one in five cases, the result will be falsely declared negative using these methods. However, this method can be deployed with limited funds.
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Affiliation(s)
- Noé Patrick M'Bondoukwé
- Department of Parasitology-Mycology-Tropical Medicine, Faculty of Medicine, Université des Sciences de la Santé, 4009, Libreville, Gabon.
| | - Matthieu Owono-Medang
- Department of Parasitology-Mycology-Tropical Medicine, Faculty of Medicine, Université des Sciences de la Santé, 4009, Libreville, Gabon
| | - Marie Noëlle Moussavou-Boussougou
- Department of Parasitology-Mycology-Tropical Medicine, Faculty of Medicine, Université des Sciences de la Santé, 4009, Libreville, Gabon
| | - Yvan Akoue
- Department of Parasitology-Mycology-Tropical Medicine, Faculty of Medicine, Université des Sciences de la Santé, 4009, Libreville, Gabon
| | - Valentin Migueba
- Department of Parasitology-Mycology-Tropical Medicine, Faculty of Medicine, Université des Sciences de la Santé, 4009, Libreville, Gabon
| | - Dmitry Bulaev
- Competence Centre for Methodology and Statistics, Luxembourg Institute of Health, 1A-B Rue Thomas Edison, 1445, Strassen, Luxembourg
| | - Anouk Neven
- Competence Centre for Methodology and Statistics, Luxembourg Institute of Health, 1A-B Rue Thomas Edison, 1445, Strassen, Luxembourg
| | - Luice Aurtin Joel James
- Department of Parasitology-Mycology-Tropical Medicine, Faculty of Medicine, Université des Sciences de la Santé, 4009, Libreville, Gabon
| | - Sylvie Alberte Ntsame Ella
- Programme de Lutte Contre les Maladies Parasitaires, Ministère de la Santé du Gabon, Libreville, Gabon
| | - Denise Patricia Mawili-Mboumba
- Department of Parasitology-Mycology-Tropical Medicine, Faculty of Medicine, Université des Sciences de la Santé, 4009, Libreville, Gabon
| | - Julienne Atsame
- Programme de Lutte Contre les Maladies Parasitaires, Ministère de la Santé du Gabon, Libreville, Gabon
| | - Michel Vaillant
- Competence Centre for Methodology and Statistics, Luxembourg Institute of Health, 1A-B Rue Thomas Edison, 1445, Strassen, Luxembourg
| | - Marielle Karine Bouyou Akotet
- Department of Parasitology-Mycology-Tropical Medicine, Faculty of Medicine, Université des Sciences de la Santé, 4009, Libreville, Gabon
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2
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Rotejanaprasert C, Chuaicharoen P, Prada JM, Thantithaveewat T, Adisakwattana P, Pan-ngum W. Evaluation of Kato-Katz and multiplex quantitative polymerase chain reaction performance for clinical helminth infections in Thailand using a latent class analysis. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220281. [PMID: 37598708 PMCID: PMC10440171 DOI: 10.1098/rstb.2022.0281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Accepted: 05/27/2023] [Indexed: 08/22/2023] Open
Abstract
Using an appropriate diagnostic tool is essential to soil-transmitted helminth control and elimination efforts. Kato-Katz (KK) is the most commonly used diagnostic, but recently other tools, such as real-time quantitative polymerase chain reaction (multiplex qPCR), are starting to be employed more. Here, we evaluated the performance of these two diagnostic tools for five helminth species in Thailand. In the absence of a gold standard, diagnostic performance can be evaluated using latent class analysis. Our results suggest that in moderate to high prevalence settings above 2% multiplex qPCR could be more sensitive than KK, this was particularly apparent for Opisthorchis viverrini in the northeastern provinces. However, for low prevalence, both diagnostics suffered from low sensitivity. Specificity of both diagnostics was estimated to be high (above 70%) across all settings. For some specific helminth infection such as O. viverrini, multiplex qPCR is still a preferable choice of diagnostic test. KK performed equally well in detecting Ascaris lumbricoides and Taenia solium when the prevalence is moderate to high (above 2%). Neither test performed well when the prevalence of infection is low (below 2%), and certainly in the case for hookworm and Trichuris trichiura. Combination of two or more diagnostic tests can improve the performance although the cost would be high. Development of new methods for helminth surveillance at the pre-elimination phase is therefore very important. This article is part of the theme issue 'Challenges and opportunities in the fight against neglected tropical diseases: a decade from the London Declaration on NTDs'.
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Affiliation(s)
- Chawarat Rotejanaprasert
- Department of Tropical Hygiene, Mahidol University, Bangkok, Thailand
- Mahidol-Oxford Tropical Medicine Research Unit (MORU), Mahidol University, Bangkok, Thailand
| | | | - Joaquin M. Prada
- Faculty of Health and Medical Sciences, School of Veterinary Medicine, University of Surrey, Guildford, UK
| | | | - Poom Adisakwattana
- Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Wirichada Pan-ngum
- Department of Tropical Hygiene, Mahidol University, Bangkok, Thailand
- Mahidol-Oxford Tropical Medicine Research Unit (MORU), Mahidol University, Bangkok, Thailand
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3
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Slater HC, Ding XC, Knudson S, Bridges DJ, Moonga H, Saad NJ, De Smet M, Bennett A, Dittrich S, Slutsker L, Domingo GJ. Performance and utility of more highly sensitive malaria rapid diagnostic tests. BMC Infect Dis 2022; 22:121. [PMID: 35120441 PMCID: PMC8815208 DOI: 10.1186/s12879-021-07023-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 12/30/2021] [Indexed: 12/03/2022] Open
Abstract
Background A new more highly sensitive rapid diagnostic test (HS-RDT) for Plasmodium falciparum malaria (Alere™/Abbott Malaria Ag P.f RDT [05FK140], now called NxTek™ Eliminate Malaria Ag Pf) was launched in 2017. The test has already been used in many research studies in a wide range of geographies and use cases. Methods In this study, we collate all published and available unpublished studies that use the HS-RDT and assess its performance in (i) prevalence surveys, (ii) clinical diagnosis, (iii) screening pregnant women, and (iv) active case detection. Two individual-level data sets from asymptomatic populations are used to fit logistic regression models to estimate the probability of HS-RDT positivity based on histidine-rich protein 2 (HRP2) concentration and parasite density. The performance of the HS-RDT in prevalence surveys is estimated by calculating the sensitivity and positive proportion in comparison to polymerase chain reaction (PCR) and conventional malaria RDTs. Results We find that across 18 studies, in prevalence surveys, the mean sensitivity of the HS-RDT is estimated to be 56.1% (95% confidence interval [CI] 46.9–65.4%) compared to 44.3% (95% CI 32.6–56.0%) for a conventional RDT (co-RDT) when using nucleic acid amplification techniques as the reference standard. In studies where prevalence was estimated using both the HS-RDT and a co-RDT, we found that prevalence was on average 46% higher using a HS-RDT compared to a co-RDT. For use in clinical diagnosis and screening pregnant women, the HS-RDT was not significantly more sensitive than a co-RDT. Conclusions Overall, the evidence presented here suggests that the HS-RDT is more sensitive in asymptomatic populations and could provide a marginal improvement in clinical diagnosis and screening pregnant women. Although the HS-RDT has limited temperature stability and shelf-life claims compared to co-RDTs, there is no evidence to suggest, given this test has the same cost as current RDTs, it would have any negative impacts in terms of malaria misdiagnosis if it were widely used in all four population groups explored here. Supplementary Information The online version contains supplementary material available at 10.1186/s12879-021-07023-5.
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Affiliation(s)
- Hannah C Slater
- Diagnostics Program, PATH, Seattle, WA, USA. .,Malaria and Neglected Tropical Diseases, PATH, Seattle, WA, USA.
| | - Xavier C Ding
- Foundation for Innovative New Diagnostics, Geneva, Switzerland
| | | | - Daniel J Bridges
- PATH Malaria Control and Elimination Partnership in Africa (MACEPA), Lusaka, Zambia
| | - Hawela Moonga
- National Malaria Elimination Centre, Zambia Ministry of Health, Lusaka, Zambia
| | - Neil J Saad
- Médecins Sans Frontières, Phnom Penh, Preah Vihear, Cambodia
| | | | - Adam Bennett
- Malaria and Neglected Tropical Diseases, PATH, Seattle, WA, USA.,Malaria Elimination Initiative, Global Health Group, University of California San Francisco, San Francisco, CA, USA
| | - Sabine Dittrich
- Foundation for Innovative New Diagnostics, Geneva, Switzerland
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4
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Doolan CP, Louie T, Lata C, Larios OE, Stokes W, Kim J, Brown K, Beck P, Deardon R, Pillai DR. Latent class analysis for the diagnosis of Clostridioides difficile infection. Clin Infect Dis 2020; 73:e2673-e2679. [PMID: 33053174 DOI: 10.1093/cid/ciaa1553] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Clostridioides difficile infection (CDI) is an opportunistic disease that lacks a gold standard test. Nucleic acid amplification tests (NAATs) such as real-time PCR demonstrate excellent an limit of detection (LOD) whereas antigenic methods are able to detect free toxin. Latent class analysis (LCA) provides an unbiased statistical approach to resolving true disease. METHODS A cross-sectional study was conducted with suspected CDI patients (n=96). Four commercial real-time PCR tests, toxin antigen detection by enzyme immunoassay (EIA), toxigenic culture, and fecal calprotectin were performed. CDI clinical diagnosis was determined by consensus majority of three experts. LCA was performed using laboratory and clinical variables independent of any gold standard. RESULTS Six LCA models were generated to determine CDI probability using four variables including toxin EIA, toxigenic culture, clinical diagnosis, and fecal calprotectin levels. Three defined zones as a function of real-time PCR cycle threshold (Ct) were identified using LCA: CDI likely (>90% probability), equivocal (<90% and >10%), CDI unlikely (<10%). A single model comprising toxigenic culture, clinical diagnosis, and toxin EIA showed the best fitness. The following Ct cut-offs for four commercial test platforms were obtained using this model to delineate three CDI probability zones: [GeneXpert ® : 24.00, 33.61], [Simplexa ® 28.97, 36.85], [Elite MGB ® 30.18, 37.43], and [BD Max ™ 27.60, 34.26]. CONCLUSION The clinical implication of applying LCA to CDI is to report Ct values assigned to probability zones based on the commercial real-time PCR platform. A broad range of equivocation suggests clinical judgement is essential to the confirmation of CDI.
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Affiliation(s)
- Cody P Doolan
- Clinical Section of Microbiology, Alberta Precision Laboratories, Calgary, AB, Canada.,Department of Microbiology, Immunology, and Infectious Diseases, University of Calgary, AB, Canada.,Department Pathology and Laboratory Medicine, University of Calgary, Calgary, AB, Canada
| | - Thomas Louie
- Clinical Section of Infectious Diseases, Department of Medicine, University of Calgary, Calgary, AB, Canada
| | | | - Oscar E Larios
- Clinical Section of Microbiology, Alberta Precision Laboratories, Calgary, AB, Canada.,Department Pathology and Laboratory Medicine, University of Calgary, Calgary, AB, Canada.,Clinical Section of Infectious Diseases, Department of Medicine, University of Calgary, Calgary, AB, Canada
| | - William Stokes
- Clinical Section of Microbiology, Alberta Precision Laboratories, Calgary, AB, Canada.,Department Pathology and Laboratory Medicine, University of Calgary, Calgary, AB, Canada.,Clinical Section of Infectious Diseases, Department of Medicine, University of Calgary, Calgary, AB, Canada
| | - Joseph Kim
- Clinical Section of Infectious Diseases, Department of Medicine, University of Calgary, Calgary, AB, Canada
| | - Kristen Brown
- Clinical Section of Microbiology, Alberta Precision Laboratories, Calgary, AB, Canada.,Department Pathology and Laboratory Medicine, University of Calgary, Calgary, AB, Canada.,Clinical Section of Infectious Diseases, Department of Medicine, University of Calgary, Calgary, AB, Canada
| | - Paul Beck
- Clinical Section of Gastroenterology, Department of Medicine, University of Calgary, Calgary, AB, Canada
| | - Rob Deardon
- Department of Mathematics and Statistics, Faculty of Science, University of Calgary, Calgary, AB, Canada.,Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - Dylan R Pillai
- Clinical Section of Microbiology, Alberta Precision Laboratories, Calgary, AB, Canada.,Department of Microbiology, Immunology, and Infectious Diseases, University of Calgary, AB, Canada.,Department Pathology and Laboratory Medicine, University of Calgary, Calgary, AB, Canada.,Clinical Section of Infectious Diseases, Department of Medicine, University of Calgary, Calgary, AB, Canada
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5
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Kamau A, Mtanje G, Mataza C, Malla L, Bejon P, Snow RW. The relationship between facility-based malaria test positivity rate and community-based parasite prevalence. PLoS One 2020; 15:e0240058. [PMID: 33027313 PMCID: PMC7540858 DOI: 10.1371/journal.pone.0240058] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 09/17/2020] [Indexed: 02/06/2023] Open
Abstract
INTRODUCTION Malaria surveillance is a key pillar in the control of malaria in Africa. The value of using routinely collected data from health facilities to define malaria risk at community levels remains poorly defined. METHODS Four cross-sectional parasite prevalence surveys were undertaken among residents at 36 enumeration zones in Kilifi county on the Kenyan coast and temporally and spatially matched to fever surveillance at 6 health facilities serving the same communities over 12 months. The age-structured functional form of the relationship between test positivity rate (TPR) and community-based parasite prevalence (PR) was explored through the development of regression models fitted by alternating the linear, exponential and polynomial terms for PR. The predictive ranges of TPR were explored for PR endemicity risk groups of control programmatic value using cut-offs of low (PR <5%) and high (PR ≥ 30%) transmission intensity. RESULTS Among 28,134 febrile patients encountered for malaria diagnostic testing in the health facilities, 12,143 (43.2%: 95% CI: 42.6%, 43.7%) were positive. The overall community PR was 9.9% (95% CI: 9.2%, 10.7%) among 6,479 participants tested for malaria. The polynomial model was the best fitting model for the data that described the algebraic relationship between TPR and PR. In this setting, a TPR of ≥ 49% in all age groups corresponded to an age-standardized PR of ≥ 30%, while a TPR of < 40% corresponded to an age-standardized PR of < 5%. CONCLUSION A non-linear relationship was observed between the relative change in TPR and changes in the PR, which is likely to have important implications for malaria surveillance programs, especially at the extremes of transmission. However, larger, more spatially diverse data series using routinely collected TPR data matched to community-based infection prevalence data are required to explore the more practical implications of using TPR as a replacement for community PR.
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Affiliation(s)
- Alice Kamau
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom
- * E-mail:
| | - Grace Mtanje
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Christine Mataza
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Ministry of Health, Kilifi County Government, Kilifi, Kenya
| | - Lucas Malla
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Philip Bejon
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom
| | - Robert W. Snow
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom
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6
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Kotepui M, Kotepui KU, De Jesus Milanez G, Masangkay FR. Summary of discordant results between rapid diagnosis tests, microscopy, and polymerase chain reaction for detecting Plasmodium mixed infection: a systematic review and meta-analysis. Sci Rep 2020; 10:12765. [PMID: 32728145 PMCID: PMC7392751 DOI: 10.1038/s41598-020-69647-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 07/15/2020] [Indexed: 01/28/2023] Open
Abstract
Malaria rapid diagnostic tests (RDTs) are widely used to detect malaria parasites among patients who suspected malaria infections in malaria-endemic areas where microscopy is unavailable. Nevertheless, little is known about the performance of RDTs in detecting Plasmodium mixed infections. The present study aimed to evaluate the discordant results between RDTs and microscopy/polymerase chain reaction (PCR) in detecting Plasmodium mixed infections. The PubMed (MEDLINE), Web of Science, and Scopus databases were systematically reviewed to identify related studies that reported the performance of RDTs in detecting Plasmodium mixed infections. Studies were grouped according to the different RDT types including RDT type 2 (pf-HRP2/pan-aldolase), RDT type 3 (pf-HRP2/pan-pLDH), RDT type 4 (Pf-LDH/pan-pLDH), RDT type 5 (Pf/Pv-pLDH), and RDT type 6 (pf-HRP2/Pv-pLDH) for subgroup analysis. The estimates of the different proportions in each analysis group that were visually summarized in a forest plot showed the odds ratio (OR) and 95% confidence interval (CI). Plots were drawn using RevMan (version 5.3; Cochrane Community). Twenty-eight studies were included in the present study. Overall, the meta-analysis showed that RDTs could detect a significantly higher proportion of Plasmodium mixed infections than microscopy (p = 0.0007, OR = 3.33, 95% CI 1.66-6.68). Subgroup analysis demonstrated that only RDTs targeting Pf-specific histidine-rich protein 2 (HRP2)/pan-specific lactate dehydrogenase (LDH) could detect a significantly higher proportion of Plasmodium mixed infections than microscopy (p = 0.004, OR = 8.46, 95% CI 2.75-26.1). The subgroup analysis between RDTs and PCR methods demonstrated that RDTs targeting Pf-specific HRP2/Pv-specific LDH could detect a significantly lower proportion of Plasmodium mixed infections than PCR methods (p = 0.0005, OR = 0.42, 95% CI 0.26-0.68). This is the first study to summarize the discordant results between RDTs and microscopy/PCR in detecting Plasmodium mixed infections. Malaria RDTs targeting Pf-HRP2/pan-pLDH could detect a higher proportion of Plasmodium mixed infections than microscopy, while RDTs targeting Pf-HRP2/Pv-specific LDH could detect a lower proportion of Plasmodium mixed infections than PCR methods. The results of this study will support the selection and careful interpretations of RDTs for a better diagnosis of Plasmodium mixed-species infections and appropriate treatment of malaria patients in endemic and non-endemic settings.
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Affiliation(s)
- Manas Kotepui
- Medical Technology, School of Allied Health Sciences, Walailak University, Tha Sala, Nakhon Si Thammarat, Thailand.
| | - Kwuntida Uthaisar Kotepui
- Medical Technology, School of Allied Health Sciences, Walailak University, Tha Sala, Nakhon Si Thammarat, Thailand
| | - Giovanni De Jesus Milanez
- Department of Medical Technology, Institute of Arts and Sciences, Far Eastern University-Manila, Manila, Philippines
| | - Frederick Ramirez Masangkay
- Department of Medical Technology, Institute of Arts and Sciences, Far Eastern University-Manila, Manila, Philippines
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7
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Kamau A, Mtanje G, Mataza C, Mwambingu G, Mturi N, Mohammed S, Ong'ayo G, Nyutu G, Nyaguara A, Bejon P, Snow RW. Malaria infection, disease and mortality among children and adults on the coast of Kenya. Malar J 2020; 19:210. [PMID: 32552891 PMCID: PMC7301992 DOI: 10.1186/s12936-020-03286-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2020] [Accepted: 06/12/2020] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Malaria transmission has recently fallen in many parts of Africa, but systematic descriptions of infection and disease across all age groups are rare. Here, an epidemiological investigation of parasite prevalence, the incidence of fevers associated with infection, severe hospitalized disease and mortality among children older than 6Â months and adults on the Kenyan coast is presented. METHODS A prospective fever surveillance was undertaken at 6 out-patients (OPD) health-facilities between March 2018 and February 2019. Four community-based, cross sectional surveys of fever history and infection prevalence were completed among randomly selected homestead members from the same communities. Paediatric and adult malaria at Kilifi county hospital was obtained for the 12Â months period. Rapid Diagnostic Tests (CareStartâ„¢ RDT) to detect HRP2-specific to Plasmodium falciparum was used in the community and the OPD, and microscopy in the hospital. Crude and age-specific incidence rates were computed using Poisson regression. RESULTS Parasite prevalence gradually increased from childhood, reaching 12% by 9Â years of age then declining through adolescence into adulthood. The incidence rate of RDT positivity in the OPD followed a similar trend to that of infection prevalence in the community. The incidence of hospitalized malaria from the same community was concentrated among children aged 6Â months to 4Â years (i.e. 64% and 70% of all hospitalized and severe malaria during the 12Â months of surveillance, respectively). Only 3.7% (12/316) of deaths were directly attributable to malaria. Malaria mortality was highest among children aged 6Â months-4Â years at 0.57 per 1000 person-years (95% CI 0.2, 1.2). Severe malaria and death from malaria was negligible above 15Â years of age. CONCLUSION Under conditions of low transmission intensity, immunity to disease and the fatal consequences of infection appear to continue to be acquired in childhood and faster than anti-parasitic immunity. There was no evidence of an emerging significant burden of severe malaria or malaria mortality among adults. This is contrary to current modelled approaches to disease burden estimation in Africa and has important implications for the targeting of infection prevention strategies based on chemoprevention or vector control.
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Affiliation(s)
- Alice Kamau
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.
| | - Grace Mtanje
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Christine Mataza
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Ministry of Health, Kilifi County Government, Kilifi, Kenya
| | | | - Neema Mturi
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | | | - Gideon Nyutu
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Amek Nyaguara
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Philip Bejon
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Robert W Snow
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
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