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Bareng PN, Grignard L, Reyes R, Fornace K, Spencer F, Macalinao ML, Luchavez J, Espino FE, Drakeley C, Hafalla JCR. Prevalence and temporal changes of mutations linked to anti-malarial drug resistance in Plasmodium falciparum and Plasmodium vivax in Palawan, Philippines. Int J Infect Dis 2021; 116:174-181. [PMID: 34883232 PMCID: PMC8866131 DOI: 10.1016/j.ijid.2021.12.318] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 11/24/2021] [Accepted: 12/02/2021] [Indexed: 11/30/2022] Open
Abstract
Plasmodium falciparum and Plasmodium vivax isolates from the Philippines were analysed. Varying mutations were found in markers linked to resistance to antimalarial drugs. None of the mutations were particularly of high prevalence. Clear temporal patterns in these mutations were observed within the past 15 years. Decrease in pfcrt and pfmdr mutations are in line with antimalarial policy change.
Objective This study provides 2016 data on the prevalence of key single nucleotide polymorphisms (SNPs) associated with antimalarial drug resistance in Palawan, Philippines. Findings were combined with historical data to model temporal changes in the prevalence of these SNPs in Plasmodium isolates. Methods Plasmodium isolates were genotyped using drug resistance markers pfmdr1, pfcrt, pfdhfr, pfdhps, kelch-13, pvmdr1, pvdhfr, and pvdhps. Temporal trends in the probability of mutations were estimated as a function of time using a binomial generalised linear model. Results All samples sequenced for Plasmodium falciparum chloroquine markers pfmdr1 and pfcrt had wild-type alleles. Varying mutation patterns were observed for the sulphadoxine/pyrimethamine markers pfdhps and pfdhfr; complete quintuplet mutations were not found. No SNPs were observed for the artemisinin marker kelch-13. For Plasmodium vivax, differing patterns were detected for pvmdr1, pvdhfr, and pvdhps. Conclusions The study findings suggest that the current drugs remain effective and that there is limited importation and establishment of resistant parasites in the area. Clear temporal trends were recognised, with prominent decreases in the proportions of pfcrt and pfmdr mutations detected within the past 15 years, consistent with a change in antimalarial drug policy. Continuous surveillance of antimalarial drug resistance is important to support malaria elimination efforts.
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Affiliation(s)
- Paolo N Bareng
- Department of Parasitology and National Reference Centre for Malaria and Other Parasites, Research Institute for Tropical Medicine, Department of Health, Muntinlupa City, Philippines.
| | - Lynn Grignard
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Ralph Reyes
- Department of Parasitology and National Reference Centre for Malaria and Other Parasites, Research Institute for Tropical Medicine, Department of Health, Muntinlupa City, Philippines
| | - Kim Fornace
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Freya Spencer
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Ma Lourdes Macalinao
- Department of Parasitology and National Reference Centre for Malaria and Other Parasites, Research Institute for Tropical Medicine, Department of Health, Muntinlupa City, Philippines
| | - Jennifer Luchavez
- Department of Parasitology and National Reference Centre for Malaria and Other Parasites, Research Institute for Tropical Medicine, Department of Health, Muntinlupa City, Philippines
| | - Fe Esperanza Espino
- Department of Parasitology and National Reference Centre for Malaria and Other Parasites, Research Institute for Tropical Medicine, Department of Health, Muntinlupa City, Philippines
| | - Chris Drakeley
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Julius Clemence R Hafalla
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
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2
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Horning MP, Delahunt CB, Bachman CM, Luchavez J, Luna C, Hu L, Jaiswal MS, Thompson CM, Kulhare S, Janko S, Wilson BK, Ostbye T, Mehanian M, Gebrehiwot R, Yun G, Bell D, Proux S, Carter JY, Oyibo W, Gamboa D, Dhorda M, Vongpromek R, Chiodini PL, Ogutu B, Long EG, Tun K, Burkot TR, Lilley K, Mehanian C. Performance of a fully-automated system on a WHO malaria microscopy evaluation slide set. Malar J 2021; 20:110. [PMID: 33632222 PMCID: PMC7905596 DOI: 10.1186/s12936-021-03631-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Revised: 02/04/2021] [Accepted: 02/06/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Manual microscopy remains a widely-used tool for malaria diagnosis and clinical studies, but it has inconsistent quality in the field due to variability in training and field practices. Automated diagnostic systems based on machine learning hold promise to improve quality and reproducibility of field microscopy. The World Health Organization (WHO) has designed a 55-slide set (WHO 55) for their External Competence Assessment of Malaria Microscopists (ECAMM) programme, which can also serve as a valuable benchmark for automated systems. The performance of a fully-automated malaria diagnostic system, EasyScan GO, on a WHO 55 slide set was evaluated. METHODS The WHO 55 slide set is designed to evaluate microscopist competence in three areas of malaria diagnosis using Giemsa-stained blood films, focused on crucial field needs: malaria parasite detection, malaria parasite species identification (ID), and malaria parasite quantitation. The EasyScan GO is a fully-automated system that combines scanning of Giemsa-stained blood films with assessment algorithms to deliver malaria diagnoses. This system was tested on a WHO 55 slide set. RESULTS The EasyScan GO achieved 94.3 % detection accuracy, 82.9 % species ID accuracy, and 50 % quantitation accuracy, corresponding to WHO microscopy competence Levels 1, 2, and 1, respectively. This is, to our knowledge, the best performance of a fully-automated system on a WHO 55 set. CONCLUSIONS EasyScan GO's expert ratings in detection and quantitation on the WHO 55 slide set point towards its potential value in drug efficacy use-cases, as well as in some case management situations with less stringent species ID needs. Improved runtime may enable use in general case management settings.
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Affiliation(s)
- Matthew P Horning
- Global Health Labs (formerly at Intellectual Ventures Laboratory/Global Good), 14360 SE Eastgate Way, Bellevue, WA, 98007, USA.
| | - Charles B Delahunt
- Global Health Labs (formerly at Intellectual Ventures Laboratory/Global Good), 14360 SE Eastgate Way, Bellevue, WA, 98007, USA.,Applied Math Department, University of Washington, Seattle, WA, 98195, USA
| | - Christine M Bachman
- Global Health Labs (formerly at Intellectual Ventures Laboratory/Global Good), 14360 SE Eastgate Way, Bellevue, WA, 98007, USA
| | | | - Christian Luna
- Research Institute for Tropical Medicine, Muntinlupa, Philippines
| | - Liming Hu
- Global Health Labs (formerly at Intellectual Ventures Laboratory/Global Good), 14360 SE Eastgate Way, Bellevue, WA, 98007, USA
| | - Mayoore S Jaiswal
- formerly Intellectual Ventures Laboratory, 3150 139th AVE SE, Bellevue, WA, 98005, USA
| | | | - Sourabh Kulhare
- Global Health Labs (formerly at Intellectual Ventures Laboratory/Global Good), 14360 SE Eastgate Way, Bellevue, WA, 98007, USA
| | | | - Benjamin K Wilson
- Global Health Labs (formerly at Intellectual Ventures Laboratory/Global Good), 14360 SE Eastgate Way, Bellevue, WA, 98007, USA
| | - Travis Ostbye
- Global Health Labs (formerly at Intellectual Ventures Laboratory/Global Good), 14360 SE Eastgate Way, Bellevue, WA, 98007, USA
| | - Martha Mehanian
- Global Health Labs (formerly at Intellectual Ventures Laboratory/Global Good), 14360 SE Eastgate Way, Bellevue, WA, 98007, USA
| | - Roman Gebrehiwot
- formerly Intellectual Ventures Laboratory, 3150 139th AVE SE, Bellevue, WA, 98005, USA
| | - Grace Yun
- formerly Intellectual Ventures Laboratory, 3150 139th AVE SE, Bellevue, WA, 98005, USA
| | - David Bell
- Independent Consultant, Issaquah, WA, USA
| | - Stephane Proux
- Shoklo Malaria Research Unit, Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | | | | | - Dionicia Gamboa
- Laboratorios de Investigacion y Desarrollo, Facultad de Ciencias y Filosofia, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Mehul Dhorda
- World Wide Antimalarial Resistance Network and Mahidol-Oxford Tropical Medicine Research Unit, Bangkok, Thailand
| | - Ranitha Vongpromek
- Infectious Diseases Data Observatory and World Wide Antimalarial Resistance Network, Asia- Pacific Regional Centre, Bangkok, Thailand
| | - Peter L Chiodini
- Hospital for Tropical Diseases and the London School of Hygiene and Tropical Medicine, London, UK
| | | | - Earl G Long
- Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Kyaw Tun
- Defence Services Medical Academy, Mingaladon, Myanmar
| | - Thomas R Burkot
- Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Australia
| | - Ken Lilley
- Australian Defence Force Malaria and Infectious Disease Institute, Enoggera, Australia
| | - Courosh Mehanian
- Global Health Labs (formerly at Intellectual Ventures Laboratory/Global Good), 14360 SE Eastgate Way, Bellevue, WA, 98007, USA
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van den Hoogen LL, Bareng P, Alves J, Reyes R, Macalinao M, Rodrigues JM, Fernandes JM, Goméz LF, Hall T, Singh SK, Fornace K, Luchavez J, Kitchen A, Chiodini P, Espino F, Tetteh KKA, Stresman G, Sepúlveda N, Drakeley C. Comparison of Commercial ELISA Kits to Confirm the Absence of Transmission in Malaria Elimination Settings. Front Public Health 2020; 8:480. [PMID: 33014975 PMCID: PMC7509087 DOI: 10.3389/fpubh.2020.00480] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 07/28/2020] [Indexed: 11/13/2022] Open
Abstract
Background: Antimalarial antibody measurements are useful because they reflect historical and recent exposure to malaria. As such, they may provide additional information to assess ongoing transmission in low endemic or pre-elimination settings where cases are rare. In addition, the absence of antibody responses in certain individuals can indicate the cessation of transmission. Commercial malaria enzyme-linked immunosorbent assays (ELISA) detect antimalarial antibodies and are commonly used to screen blood donations for possible malaria infection. However, there is no standardized test to detect antimalarial antibodies for epidemiological use. Here we compared five commercially available ELISA kits (Trinity Biotech, newbio, DiaPro, Cellabs, and NovaTec) in search of a standardized tool for supporting claims of absence of malaria transmission. For comparison, a research-based (RB) ELISA protocol was performed alongside the commercial kits. Results: The commercial kits were first compared using serum samples from known malaria-unexposed individuals (n = 223) and Toxoplasma-infected individuals (n = 191) to assess specificity and cross-reactivity against non-malaria infections. In addition, 134 samples from ≥10-year-olds collected in a hyperendemic region in the Gambia in the early 1990s were used to assess sensitivity. Three out of five kits showed high sensitivity (90–92%), high specificity (98–99%), low cross-reactivity (0–3%) and were considered user-friendly (Trinity Biotech, newbio and NovaTec). Two of these kits (Trinity Biotech and NovaTec) were taken forward for epidemiological evaluation and results were compared to those using the RB-ELISA. Samples from two pre-elimination settings (Praia, Cape Verde; n = 1,396, and Bataan, the Philippines; n = 1,824) were tested. Serological results from both the Trinity Biotech kit and the RB-ELISA concurred with recent passively detected case counts in both settings. Results from the Trinity Biotech kit reflected a significant decrease in the number of reported cases in Bataan in the 1990s better than the RB-ELISA. Results from the NovaTec kit did not reflect transmission patterns in either setting. Conclusion: The Trinity Biotech commercial ELISA kit was considered reliable for epidemiological use and accurately described transmission patterns in two (previously) malaria endemic settings. The use of this simple and standardized serological tool may aid national control and elimination programs by confirming that regions are free from malaria.
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Affiliation(s)
- Lotus L van den Hoogen
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Paolo Bareng
- Department of Health, Research Institute for Tropical Medicine, Manila, Philippines
| | - Joana Alves
- National Institute of Public Health, Praia, Cape Verde
| | - Ralph Reyes
- Department of Health, Research Institute for Tropical Medicine, Manila, Philippines
| | - Malou Macalinao
- Department of Health, Research Institute for Tropical Medicine, Manila, Philippines
| | | | - José M Fernandes
- Faculty of Science and Technology, University of Cape Verde, Praia, Cape Verde
| | - Lara F Goméz
- Department of Natural, Life and Environmental Sciences, Jean Piaget University of Cape Verde, Praia, Cape Verde
| | - Tom Hall
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Susheel K Singh
- Department of Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark.,Department of Immunology and Microbiology, Centre for Medical Parasitology, University of Copenhagen, Copenhagen, Denmark
| | - Kimberly Fornace
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Jennifer Luchavez
- Department of Health, Research Institute for Tropical Medicine, Manila, Philippines
| | - Alan Kitchen
- NHS Blood and Transplant, London, United Kingdom
| | - Peter Chiodini
- Hospital for Tropical Diseases and London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Fe Espino
- Department of Health, Research Institute for Tropical Medicine, Manila, Philippines
| | - Kevin K A Tetteh
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Gillian Stresman
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Nuno Sepúlveda
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom.,Centre of Statistics and Applications, University of Lisbon, Lisbon, Portugal
| | - Chris Drakeley
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
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4
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Incardona S, Bell D, Campillo A, Cunningham J, Ariey F, Fandeur T, Luchavez J, Luna CA, Ménard D, Nhem S, Sornillo JB, Witkowski B, Katz Z, Dittrich S, Ding XC. Keep the quality high: the benefits of lot testing for the quality control of malaria rapid diagnostic tests. Malar J 2020; 19:247. [PMID: 32660630 PMCID: PMC7359453 DOI: 10.1186/s12936-020-03324-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 07/07/2020] [Indexed: 11/30/2022] Open
Abstract
Background The production and use of malaria rapid diagnostic tests (RDTs) has risen dramatically over the past 20 years. In view of weak or non-existing in vitro diagnostics (IVD) regulations and post-marketing surveillance (PMS) systems in malaria endemic countries, the World Health Organization, later joined by the Foundation for Innovative New Diagnostics, established an independent, centralized performance evaluation and Lot Testing (LT) programme to safeguard against poor quality of RDTs being distributed through the public health sector of malaria endemic countries. RDT performances and manufacturer quality management systems have evolved over the past decade raising questions about the future need for a centralized LT programme. Results Between 2007 and 2017, 6056 lots have been evaluated, representing approximately 1.6 Billion RDTs. A total of 69 lots (1.1%) failed the quality control. Of these failures, 26 were detected at receipt of the RDT lot in the LT laboratory, representing an estimated 7.9 million poor quality RDTs, and LT requesters were advised that RDTs were not of sufficient quality for use in patient management. Forty-three were detected after long-term storage in the laboratory, of which 24 (56%) were found to be due to a major issue with insufficient buffer volume in single use buffer vials, others predominantly showing loss of sensitivity. The annual cost of running the programme, based on expenses recorded in years 2014–2016, an estimated volume of 700 lots per year and including replenishment of quality control samples, was estimated at US$ 178,500 ($US 255 per lot tested). Conclusions Despite the clear benefits of the centralized LT programme and its low cost compared with the potential costs of each country establishing its own PMS system for RDTs, funding concerns have made its future beyond 2020 uncertain. In order to manage the risks of misdiagnosis due to low quality RDTs, and to ensure the continued safety and reliability of malaria case management, there is a need to ensure that an effective and implementable approach to RDT quality control continues to be available to programmes in endemic countries.
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Affiliation(s)
| | - David Bell
- Independent consultant, Issaquah, WA, USA
| | | | - Jane Cunningham
- World Health Organization/Global Malaria Programme (WHO/GMP), Geneva, Switzerland
| | - Frederic Ariey
- Hôpital Cochin, Laboratoire de Parasitologie-Mycologie, INSERM U1016 (Institut Cochin), Université de Paris, Paris, France
| | - Thierry Fandeur
- Direction Internationale, Institut Pasteur de Paris, Paris, France
| | - Jennifer Luchavez
- Parasitology Department, Research Institute for Tropical Medicine, Muntinlupa, Philippines
| | - Christian Anthony Luna
- Parasitology Department, Research Institute for Tropical Medicine, Muntinlupa, Philippines
| | - Didier Ménard
- Malaria Genetics and Resistance Unit, Parasites and Insect Vectors Department, Institut Pasteur, Paris, France
| | - Sina Nhem
- National Center for Entomology, Parasitology and Malaria Control, Phnom Penh, Cambodia
| | - Johanna Beulah Sornillo
- Epidemiology and Biostatistics Department, Research Institute for Tropical Medicine, Muntinlupa, Philippines
| | - Benoit Witkowski
- Laboratoire d'Epidémiologie Moléculaire du Paludisme, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | | | - Sabine Dittrich
- FIND, Geneva, Switzerland.,Nuffield School of Medicine, University of Oxford, Oxford, UK
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5
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Cunningham J, Jones S, Gatton ML, Barnwell JW, Cheng Q, Chiodini PL, Glenn J, Incardona S, Kosack C, Luchavez J, Menard D, Nhem S, Oyibo W, Rees-Channer RR, Gonzalez I, Bell D. A review of the WHO malaria rapid diagnostic test product testing programme (2008-2018): performance, procurement and policy. Malar J 2019; 18:387. [PMID: 31791354 PMCID: PMC6889598 DOI: 10.1186/s12936-019-3028-z] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 11/21/2019] [Indexed: 11/10/2022] Open
Abstract
Malaria rapid diagnostic tests (RDTs) emerged in the early 1990s into largely unregulated markets, and uncertain field performance was a major concern for the acceptance of tests for malaria case management. This, combined with the need to guide procurement decisions of UN agencies and WHO Member States, led to the creation of an independent, internationally coordinated RDT evaluation programme aiming to provide comparative performance data of commercially available RDTs. Products were assessed against Plasmodium falciparum and Plasmodium vivax samples diluted to two densities, along with malaria-negative samples from healthy individuals, and from people with immunological abnormalities or non-malarial infections. Three measures were established as indicators of performance, (i) panel detection score (PDS) determined against low density panels prepared from P. falciparum and P. vivax wild-type samples, (ii) false positive rate, and (iii) invalid rate, and minimum criteria defined. Over eight rounds of the programme, 332 products were tested. Between Rounds 1 and 8, substantial improvements were seen in all performance measures. The number of products meeting all criteria increased from 26.8% (11/41) in Round 1, to 79.4% (27/34) in Round 8. While products submitted to further evaluation rounds under compulsory re-testing did not show improvement, those voluntarily resubmitted showed significant increases in P. falciparum (p = 0.002) and P. vivax PDS (p < 0.001), with more products meeting the criteria upon re-testing. Through this programme, the differentiation of products based on comparative performance, combined with policy changes has been influential in the acceptance of malaria RDTs as a case-management tool, enabling a policy of parasite-based diagnosis prior to treatment. Publication of product testing results has produced a transparent market allowing users and procurers to clearly identify appropriate products for their situation, and could form a model for introduction of other, broad-scale diagnostics.
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Affiliation(s)
- Jane Cunningham
- World Health Organization (WHO), Global Malaria Programme, 20 Appia Avenue, 1211, Geneva, Switzerland.
| | - Sophie Jones
- Independent Consultant, Bedford Hill, Balham, London, SW12 9HR, UK.,Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention (CDC), Bldg. 23, Room 10-169, 1600 Clifton Road, Mailstop D-67, Atlanta, GA, 30329, USA
| | - Michelle L Gatton
- School of Public Health and Social Work, Queensland University of Technology (QUT), 2 George St, Brisbane, QLD, Australia
| | - John W Barnwell
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention (CDC), Atlanta, GA, 30329, USA
| | - Qin Cheng
- Australian Defence Force Malaria and Infectious Disease Institute (ADFMIDI), Gallipoli Barracks Enoggera, 4051, Brisbane, Australia
| | - Peter L Chiodini
- Department of Clinical Parasitology, Hospital for Tropical Diseases (HTD), Mortimer Market Centre, Mortimer Market, Capper St, Fitzrovia, London, UK.,London School of Hygiene and Tropical Medicine (LSHTM), London, UK
| | - Jeffrey Glenn
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention (CDC), Bldg. 23, Room 10-169, 1600 Clifton Road, Mailstop D-67, Atlanta, GA, 30329, USA
| | - Sandra Incardona
- Foundation for Innovative New Diagnostics (FIND), Campus Biotech, Building B, Level 0, Chemin des Mines 9, 1202, Geneva, Switzerland
| | - Cara Kosack
- Médecins Sans Frontières (MSF), Plantage Middenlaan 14, 1018 DD, Amsterdam, The Netherlands
| | - Jennifer Luchavez
- Parasitology Department of the Research Institute of Tropical Medicine (RITM), 9002 Research Dr, Alabang, Muntinlupa, The Philippines
| | - Didier Menard
- Laboratoire d'Epidémiologie Moléculaire du Paludisme, Institut Pasteur du Cambodge, Monivong Boulevard, PO 983, Phnom Penh, Cambodia
| | - Sina Nhem
- Laboratoire d'Epidémiologie Moléculaire du Paludisme, Institut Pasteur du Cambodge, Monivong Boulevard, PO 983, Phnom Penh, Cambodia
| | - Wellington Oyibo
- Department of Medical Microbiology and Parasitology, College of Medicine, University of Lagos (UL), Private Mail Bag 12003, Lagos, Nigeria
| | - Roxanne R Rees-Channer
- Department of Clinical Parasitology, Hospital for Tropical Diseases (HTD), Mortimer Market Centre, Mortimer Market, Capper St, Fitzrovia, London, UK.,Foundation for Innovative New Diagnostics (FIND), Campus Biotech, Building B, Level 0, Chemin des Mines 9, 1202, Geneva, Switzerland
| | - Iveth Gonzalez
- Foundation for Innovative New Diagnostics (FIND), Campus Biotech, Building B, Level 0, Chemin des Mines 9, 1202, Geneva, Switzerland
| | - David Bell
- Foundation for Innovative New Diagnostics (FIND), Campus Biotech, Building B, Level 0, Chemin des Mines 9, 1202, Geneva, Switzerland
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Ho MF, Baker J, Lee N, Luchavez J, Ariey F, Nhem S, Oyibo W, Bell D, González I, Chiodini P, Gatton ML, Cheng Q, McCarthy JS. Circulating antibodies against Plasmodium falciparum histidine-rich proteins 2 interfere with antigen detection by rapid diagnostic tests. Malar J 2014; 13:480. [PMID: 25481825 PMCID: PMC4295572 DOI: 10.1186/1475-2875-13-480] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 10/25/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Rapid diagnostic tests (RDTs) for detection of Plasmodium falciparum infection that target P. falciparum histidine-rich protein 2 (PfHRP2), a protein that circulates in the blood of patients infected with this species of malaria, are widely used to guide case management. Understanding determinants of PfHRP2 availability in circulation is therefore essential to understanding the performance of PfHRP2-detecting RDTs. METHODS The possibility that pre-formed host anti-PfHRP2 antibodies may block target antigen detection, thereby causing false negative test results was investigated in this study. RESULTS Anti-PfHRP2 antibodies were detected in 19/75 (25%) of plasma samples collected from patients with acute malaria from Cambodia, Nigeria and the Philippines, as well as in 3/28 (10.7%) asymptomatic Solomon Islands residents. Pre-incubation of plasma samples from subjects with high-titre anti-PfHRP2 antibodies with soluble PfHRP2 blocked the detection of the target antigen on two of the three brands of RDTs tested, leading to false negative results. Pre-incubation of the plasma with intact parasitized erythrocytes resulted in a reduction of band intensity at the highest parasite density, and a reduction of lower detection threshold by ten-fold on all three brands of RDTs tested. CONCLUSIONS These observations indicate possible reduced sensitivity for diagnosis of P. falciparum malaria using PfHRP2-detecting RDTs among people with high levels of specific antibodies and low density infection, as well as possible interference with tests configured to detect soluble PfHRP2 in saliva or urine samples. Further investigations are required to assess the impact of pre-formed anti-PfHRP2 antibodies on RDT performance in different transmission settings.
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7
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Ashraf S, Kao A, Hugo C, Christophel EM, Fatunmbi B, Luchavez J, Lilley K, Bell D. Developing standards for malaria microscopy: external competency assessment for malaria microscopists in the Asia-Pacific. Malar J 2012; 11:352. [PMID: 23095668 PMCID: PMC3502462 DOI: 10.1186/1475-2875-11-352] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 10/04/2012] [Indexed: 11/27/2022] Open
Abstract
Background Malaria diagnosis has received renewed interest in recent years, associated with the increasing accessibility of accurate diagnosis through the introduction of rapid diagnostic tests and new World Health Organization guidelines recommending parasite-based diagnosis prior to anti-malarial therapy. However, light microscopy, established over 100 years ago and frequently considered the reference standard for clinical diagnosis, has been neglected in control programmes and in the malaria literature and evidence suggests field standards are commonly poor. Microscopy remains the most accessible method for parasite quantitation, for drug efficacy monitoring, and as a reference of assessing other diagnostic tools. This mismatch between quality and need highlights the importance of the establishment of reliable standards and procedures for assessing and assuring quality. This paper describes the development, function and impact of a multi-country microscopy external quality assurance network set up for this purpose in Asia. Methods Surveys were used for key informants and past participants for feedback on the quality assurance programme. Competency scores for each country from 14 participating countries were compiled for analyses using paired sample t-tests. In-depth interviews were conducted with key informants including the programme facilitators and national level microscopists. Results External assessments and limited retraining through a formalized programme based on a reference slide bank has demonstrated an increase in standards of competence of senior microscopists over a relatively short period of time, at a potentially sustainable cost. The network involved in the programme now exceeds 14 countries in the Asia-Pacific, and the methods are extended to other regions. Conclusions While the impact on national programmes varies, it has translated in some instances into a strengthening of national microscopy standards and offers a possibility both for supporting revival of national microcopy programmes, and for the development of globally recognized standards of competency needed both for patient management and field research.
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Affiliation(s)
- Sania Ashraf
- Rollins School of Public Health, Emory University, Georgia, USA
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8
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Albertini A, Djalle D, Faye B, Gamboa D, Luchavez J, Mationg ML, Mwangoka G, Oyibo W, Bennett J, Incardona S, Lee E. Preliminary enquiry into the availability, price and quality of malaria rapid diagnostic tests in the private health sector of six malaria-endemic countries. Trop Med Int Health 2011; 17:147-52. [PMID: 22032415 DOI: 10.1111/j.1365-3156.2011.02904.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVES This enquiry aimed to provide a snap-shot of availability, price and quality of malaria rapid diagnostic tests (RDTs) in private health facilities at selected sites in six malaria-endemic countries in Africa, South East Asia and South America. METHODS In each study site, data collectors surveyed private healthcare facilities which were selected based on accessibility from their home institution. Using a questionnaire, information was recorded about the facility itself and the malaria RDT(s) available. Where possible, a small number of RDTs were procured and quality control tested using a standardized procedure. RESULTS Of the 324 private healthcare facilities visited, 35 outlets (mainly private clinics and hospitals) were found to supply 10 different types of RDTs products. RDT prices across the six countries ranged from US$1.00 to $16.81. Five of the 14 malaria RDTs collected failed quality control testing. CONCLUSIONS In the private outlets sampled, the availability of RDTs was limited. Some of the RDTs whose quality we tested demonstrated inadequate sensitivity. This presents a number of risks. Given the more widespread distribution of antimalarials currently planned for private sector facilities, parasite-based diagnosis in this sector will be essential to adhere to the WHO guidelines for effective case management of malaria. Considerable regulation and quality control are also necessary to assure the availability of accurate and reliable RDTs, as well as adequate case management and provider adherence to RDT results. Public sector engagement is likely to be essential in this process.
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Affiliation(s)
- A Albertini
- FIND (Foundation for Innovative New Diagnostics), Geneva, Switzerland
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Luchavez J, Baker J, Alcantara S, Belizario V, Cheng Q, McCarthy JS, Bell D. Laboratory demonstration of a prozone-like effect in HRP2-detecting malaria rapid diagnostic tests: implications for clinical management. Malar J 2011; 10:286. [PMID: 21957869 PMCID: PMC3214175 DOI: 10.1186/1475-2875-10-286] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2011] [Accepted: 09/29/2011] [Indexed: 11/20/2022] Open
Abstract
Background Malaria rapid diagnostic tests (RDTs) are now widely used for prompt on-site diagnosis in remote endemic areas where reliable microscopy is absent. Aberrant results, whereby negative test results occur at high parasite densities, have been variously reported for over a decade and have led to questions regarding the reliability of the tests in clinical use. Methods In the first trial, serial dilutions of recombinant HRP2 antigen were tested on an HRP2-detectiing RDT. In a second trial, serial dilutions of culture-derived Plasmodium falciparum parasites were tested against three HRP2-detecting RDTs. Results A prozone-like effect occurred in RDTs at a high concentration of the target antigen, histidine-rich protein-2 (above 15,000 ng/ml), a level that corresponds to more than 312000 parasites per μL. Similar results were noted on three RDT products using dilutions of cultured parasites up to a parasite density of 25%. While reduced line intensity was observed, no false negative results occurred. Conclusions These results suggest that false-negative malaria RDT results will rarely occur due to a prozone-like effect in high-density infections, and other causes are more likely. However, RDT line intensity is poorly indicative of parasite density in high-density infections and RDTs should, therefore, not be considered quantitative. Immediate management of suspected severe malaria should rely on clinical assessment or microscopy. Evaluation against high concentrations of antigen should be considered in malaria RDT product development and lot-release testing, to ensure that very weak or false negative results will not occur at antigen concentrations that might be seen clinically.
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Affiliation(s)
- Jennifer Luchavez
- Department of Parasitology, Research Institute for Tropical Medicine, Alabang, Muntinlupa City, The Philippines
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Hopkins H, Oyibo W, Luchavez J, Mationg ML, Asiimwe C, Albertini A, González IJ, Gatton ML, Bell D. Blood transfer devices for malaria rapid diagnostic tests: evaluation of accuracy, safety and ease of use. Malar J 2011; 10:30. [PMID: 21303528 PMCID: PMC3041722 DOI: 10.1186/1475-2875-10-30] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2010] [Accepted: 02/08/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria rapid diagnostic tests (RDTs) are increasingly used by remote health personnel with minimal training in laboratory techniques. RDTs must, therefore, be as simple, safe and reliable as possible. Transfer of blood from the patient to the RDT is critical to safety and accuracy, and poses a significant challenge to many users. Blood transfer devices were evaluated for accuracy and precision of volume transferred, safety and ease of use, to identify the most appropriate devices for use with RDTs in routine clinical care. METHODS Five devices, a loop, straw-pipette, calibrated pipette, glass capillary tube, and a new inverted cup device, were evaluated in Nigeria, the Philippines and Uganda. The 227 participating health workers used each device to transfer blood from a simulated finger-prick site to filter paper. For each transfer, the number of attempts required to collect and deposit blood and any spilling of blood during transfer were recorded. Perceptions of ease of use and safety of each device were recorded for each participant. Blood volume transferred was calculated from the area of blood spots deposited on filter paper. RESULTS The overall mean volumes transferred by devices differed significantly from the target volume of 5 microliters (p < 0.001). The inverted cup (4.6 microliters) most closely approximated the target volume. The glass capillary was excluded from volume analysis as the estimation method used is not compatible with this device. The calibrated pipette accounted for the largest proportion of blood exposures (23/225, 10%); exposures ranged from 2% to 6% for the other four devices. The inverted cup was considered easiest to use in blood collection (206/226, 91%); the straw-pipette and calibrated pipette were rated lowest (143/225 [64%] and 135/225 [60%] respectively). Overall, the inverted cup was the most preferred device (72%, 163/227), followed by the loop (61%, 138/227). CONCLUSIONS The performance of blood transfer devices varied in this evaluation of accuracy, blood safety, ease of use, and user preference. The inverted cup design achieved the highest overall performance, while the loop also performed well. These findings have relevance for any point-of-care diagnostics that require blood sampling.
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Affiliation(s)
- Heidi Hopkins
- Foundation for Innovative New Diagnostics, Lumumba Avenue, Kampala, Uganda.
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Baker J, Ho MF, Pelecanos A, Gatton M, Chen N, Abdullah S, Albertini A, Ariey F, Barnwell J, Bell D, Cunningham J, Djalle D, Echeverry DF, Gamboa D, Hii J, Kyaw MP, Luchavez J, Membi C, Menard D, Murillo C, Nhem S, Ogutu B, Onyor P, Oyibo W, Wang SQ, McCarthy J, Cheng Q. Global sequence variation in the histidine-rich proteins 2 and 3 of Plasmodium falciparum: implications for the performance of malaria rapid diagnostic tests. Malar J 2010; 9:129. [PMID: 20470441 PMCID: PMC2893195 DOI: 10.1186/1475-2875-9-129] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Accepted: 05/17/2010] [Indexed: 11/20/2022] Open
Abstract
Background Accurate diagnosis is essential for prompt and appropriate treatment of malaria. While rapid diagnostic tests (RDTs) offer great potential to improve malaria diagnosis, the sensitivity of RDTs has been reported to be highly variable. One possible factor contributing to variable test performance is the diversity of parasite antigens. This is of particular concern for Plasmodium falciparum histidine-rich protein 2 (PfHRP2)-detecting RDTs since PfHRP2 has been reported to be highly variable in isolates of the Asia-Pacific region. Methods The pfhrp2 exon 2 fragment from 458 isolates of P. falciparum collected from 38 countries was amplified and sequenced. For a subset of 80 isolates, the exon 2 fragment of histidine-rich protein 3 (pfhrp3) was also amplified and sequenced. DNA sequence and statistical analysis of the variation observed in these genes was conducted. The potential impact of the pfhrp2 variation on RDT detection rates was examined by analysing the relationship between sequence characteristics of this gene and the results of the WHO product testing of malaria RDTs: Round 1 (2008), for 34 PfHRP2-detecting RDTs. Results Sequence analysis revealed extensive variations in the number and arrangement of various repeats encoded by the genes in parasite populations world-wide. However, no statistically robust correlation between gene structure and RDT detection rate for P. falciparum parasites at 200 parasites per microlitre was identified. Conclusions The results suggest that despite extreme sequence variation, diversity of PfHRP2 does not appear to be a major cause of RDT sensitivity variation.
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Affiliation(s)
- Joanne Baker
- Department of Drug Resistance and Diagnostics, Australian Army Malaria Institute, Brisbane, Australia.
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Bowers KM, Bell D, Chiodini PL, Barnwell J, Incardona S, Yen S, Luchavez J, Watt H. Inter-rater reliability of malaria parasite counts and comparison of methods. Malar J 2009; 8:267. [PMID: 19939271 PMCID: PMC2789092 DOI: 10.1186/1475-2875-8-267] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Accepted: 11/25/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The introduction of artemesinin-based treatment for falciparum malaria has led to a shift away from symptom-based diagnosis. Diagnosis may be achieved by using rapid non-microscopic diagnostic tests (RDTs), of which there are many available. Light microscopy, however, has a central role in parasite identification and quantification and remains the main method of parasite-based diagnosis in clinic and hospital settings and is necessary for monitoring the accuracy of RDTs. The World Health Organization has prepared a proficiency testing panel containing a range of malaria-positive blood samples of known parasitaemia, to be used for the assessment of commercially available malaria RDTs. Different blood film and counting methods may be used for this purpose, which raises questions regarding accuracy and reproducibility. A comparison was made of the established methods for parasitaemia estimation to determine which would give the least inter-rater and inter-method variation METHODS Experienced malaria microscopists counted asexual parasitaemia on different slides using three methods; the thin film method using the total erythrocyte count, the thick film method using the total white cell count and the Earle and Perez method. All the slides were stained using Giemsa pH 7.2. Analysis of variance (ANOVA) models were used to find the inter-rater reliability for the different methods. The paired t-test was used to assess any systematic bias between the two methods, and a regression analysis was used to see if there was a changing bias with parasite count level. RESULTS The thin blood film gave parasite counts around 30% higher than those obtained by the thick film and Earle and Perez methods, but exhibited a loss of sensitivity with low parasitaemia. The thick film and Earle and Perez methods showed little or no bias in counts between the two methods, however, estimated inter-rater reliability was slightly better for the thick film method. CONCLUSION The thin film method gave results closer to the true parasite count but is not feasible at a parasitaemia below 500 parasites per microlitre. The thick film method was both reproducible and practical for this project. The determination of malarial parasitaemia must be applied by skilled operators using standardized techniques.
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Ashley EA, Touabi M, Ahrer M, Hutagalung R, Htun K, Luchavez J, Dureza C, Proux S, Leimanis M, Lwin MM, Koscalova A, Comte E, Hamade P, Page AL, Nosten F, Guerin PJ. Evaluation of three parasite lactate dehydrogenase-based rapid diagnostic tests for the diagnosis of falciparum and vivax malaria. Malar J 2009; 8:241. [PMID: 19860920 PMCID: PMC2774865 DOI: 10.1186/1475-2875-8-241] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Accepted: 10/27/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In areas where non-falciparum malaria is common rapid diagnostic tests (RDTs) capable of distinguishing malaria species reliably are needed. Such tests are often based on the detection of parasite lactate dehydrogenase (pLDH). METHODS In Dawei, southern Myanmar, three pLDH based RDTs (CareStart Malaria pLDH (Pan), CareStart Malaria pLDH (Pan, Pf) and OptiMAL-IT)were evaluated in patients presenting with clinically suspected malaria. Each RDT was read independently by two readers. A subset of patients with microscopically confirmed malaria had their RDTs repeated on days 2, 7 and then weekly until negative. At the end of the study, samples of study batches were sent for heat stability testing. RESULTS Between August and November 2007, 1004 patients aged between 1 and 93 years were enrolled in the study. Slide microscopy (the reference standard) diagnosed 213 Plasmodium vivax (Pv) monoinfections, 98 Plasmodium falciparum (Pf) mono-infections and no malaria in 650 cases. The sensitivities (sens) and specificities (spec), of the RDTs for the detection of malaria were- CareStart Malaria pLDH (Pan) test: sens 89.1% [CI95 84.2-92.6], spec 97.6% [CI95 96.5-98.4]. OptiMal-IT: Pf+/- other species detection: sens 95.2% [CI95 87.5-98.2], spec 94.7% [CI95 93.3-95.8]; non-Pf detection alone: sens 89.6% [CI95 83.6-93.6], spec 96.5% [CI95 94.8-97.7]. CareStart Malaria pLDH (Pan, Pf): Pf+/- other species: sens 93.5% [CI95 85.4-97.3], spec 97.4% [95.9-98.3]; non-Pf: sens 78.5% [CI95 71.1-84.4], spec 97.8% [CI95 96.3-98.7]. Inter-observer agreement was excellent for all tests (kappa > 0.9). The median time for the RDTs to become negative was two days for the CareStart Malaria tests and seven days for OptiMAL-IT. Tests were heat stable up to 90 days except for OptiMAL-IT (Pf specific pLDH stable to day 20 at 35 degrees C). CONCLUSION None of the pLDH-based RDTs evaluated was able to detect non-falciparum malaria with high sensitivity, particularly at low parasitaemias. OptiMAL-IT performed best overall and would perform best in an area of high malaria prevalence among screened fever cases. However, heat stability was unacceptable and the number of steps to perform this test is a significant drawback in the field. A reliable, heat-stable, highly sensitive RDT, capable of diagnosing all Plasmodium species has yet to be identified.
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Luchavez J, Espino F, Curameng P, Espina R, Bell D, Chiodini P, Nolder D, Sutherland C, Lee KS, Singh B. Human Infections with Plasmodium knowlesi, the Philippines. Emerg Infect Dis 2008; 14:811-3. [PMID: 18439369 PMCID: PMC2600254 DOI: 10.3201/eid1405.071407] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Human Infections with Plasmodium knowlesi, the Philippines Five human cases of infection with the simian malaria parasite Plasmodium knowlesi from Palawan, the Philippines, were confirmed by nested PCR. This study suggests that this zoonotic infection is found across a relatively wide area in Palawan and documents autochthonous cases in the country.
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Affiliation(s)
- Jennifer Luchavez
- Research Institute for Tropical Medicine - Parasitology, Fillinvest Compound, Alabang, Muntinlupa City, Muntinlupa 1781, the Philippines.
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Luchavez J, Lintag ME, Coll-Black M, Baik F, Bell D. An assessment of various blood collection and transfer methods used for malaria rapid diagnostic tests. Malar J 2007; 6:149. [PMID: 18001481 PMCID: PMC2194690 DOI: 10.1186/1475-2875-6-149] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Accepted: 11/15/2007] [Indexed: 11/25/2022] Open
Abstract
Background Four blood collection and transfer devices commonly used for malaria rapid diagnostic tests (RDTs) were assessed for their consistency, accuracy and ease of use in the hands of laboratory technicians and village health workers. Methods Laboratory technicians and village health workers collected blood from a finger prick using each device in random order, and deposited the blood either on filter paper or into a suitable casette-type RDT. Consistency and accuracy of volume delivered was determined by comparing the measurements of the resulting blood spots/heights with the measurements of laboratory-prepared pipetted standard volumes. The effect of varying blood volumes on RDT sensitivity and ease of use was also observed. Results There was high variability in blood volume collected by the devices, with the straw and the loop, the most preferred devices, usually transferring volumes greater than intended, while the glass capillary tube and the plastic pipette transferring less volume than intended or none at all. Varying the blood volume delivered to RDTs indicated that this variation is critical to RDT sensitivity only when the transferred volume is very low. Conclusion None of the blood transfer devices assessed performed consistently well. Adequate training on their use is clearly necessary, with more development efforts for improved designs to be used by remote health workers, in mind.
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Affiliation(s)
- Jennifer Luchavez
- Research Institute for Tropical Medicine, Filinvest Compound, Alabang, Muntinlupa, Philippines.
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Baker J, McCarthy J, Gatton M, Kyle DE, Belizario V, Luchavez J, Bell D, Cheng Q. Genetic diversity of Plasmodium falciparum histidine-rich protein 2 (PfHRP2) and its effect on the performance of PfHRP2-based rapid diagnostic tests. J Infect Dis 2005; 192:870-7. [PMID: 16088837 DOI: 10.1086/432010] [Citation(s) in RCA: 214] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2005] [Accepted: 03/16/2005] [Indexed: 11/04/2022] Open
Abstract
Rising costs of antimalarial agents are increasing the demand for accurate diagnosis of malaria. Rapid diagnostic tests (RDTs) offer great potential to improve the diagnosis of malaria, particularly in remote areas. Many RDTs are based on the detection of Plasmodium falciparum histidine-rich protein (PfHRP) 2, but reports from field tests have questioned their sensitivity and reliability. We hypothesize that the variability in the results of PfHRP2-based RDTs is related to the variability in the target antigen. We tested this hypothesis by examining the genetic diversity of PfHRP2, which includes numerous amino acid repeats, in 75 P. falciparum lines and isolates originating from 19 countries and testing a subset of parasites by use of 2 PfHRP2-based RDTs. We observed extensive diversity in PfHRP2 sequences, both within and between countries. Logistic regression analysis indicated that 2 types of repeats were predictive of RDT detection sensitivity (87.5% accuracy), with predictions suggesting that only 84% of P. falciparum parasites in the Asia-Pacific region are likely to be detected at densities < or = 250 parasites/microL. Our data also indicated that PfHRP3 may play a role in the performance of PfHRP2-based RDTs. These findings provide an alternative explanation for the variable sensitivity in field tests of malaria RDTs that is not due to the quality of the RDTs.
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Affiliation(s)
- Joanne Baker
- Department of Drug Resistance and Diagnostics, Australian Army Malaria Institute, Brisbane, Australia
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Lon CT, Alcantara S, Luchavez J, Tsuyuoka R, Bell D. Positive control wells: a potential answer to remote-area quality assurance of malaria rapid diagnostic tests. Trans R Soc Trop Med Hyg 2005; 99:493-8. [PMID: 15869776 DOI: 10.1016/j.trstmh.2005.01.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2004] [Revised: 01/11/2005] [Accepted: 01/11/2005] [Indexed: 11/23/2022] Open
Abstract
Malaria rapid diagnostic tests (RDTs) are a potential breakthrough in the provision of accurate diagnosis in remote areas, but widescale use is hampered by uncertainty over accuracy under field conditions. Positive control wells, which contain recombinant malaria parasite antigen, are a novel method for addressing this need for quality assurance. The potential of a commercially available positive control well, reconstituted with blood, was assessed for use in routine monitoring of RDT sensitivity in a remote malaria-endemic region. When maintained at 4 degrees C, the wells produced a consistent level of parasite lactate dehydrogenase (pLDH) antigen activity, as detected by pLDH-detecting RDTs, but activity reduced after cumulative exposure to temperatures likely to be encountered over a few months in a malaria-endemic area. This limitation was successfully overcome in the field through centralized, controlled storage. Monitoring of RDT sensitivity was successfully incorporated into routine supervisory visits to remote clinics. However, improved temperature stability of the wells would enhance their potential. The threshold at which the wells' signal reduced RDT sensitivity requires further investigation. The wells show potential to overcome an important obstacle to the wide implementation of accurate parasite-based diagnosis and appropriate treatment. Further assessment of their place in malaria management is warranted.
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Affiliation(s)
- C T Lon
- National Center for Parasitology, Entomology and Malaria Control, Cambodia, 372, Blv. Monivong, Corner Street 322, Phnom Penh, Cambodia
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