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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
| | | | - 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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Ramharter M, Butler J, Mombo-Ngoma G, Nordmann T, Davi SD, Zoleko Manego R. The African eye worm: current understanding of the epidemiology, clinical disease, and treatment of loiasis. THE LANCET. INFECTIOUS DISEASES 2024; 24:e165-e178. [PMID: 37858326 DOI: 10.1016/s1473-3099(23)00438-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 07/07/2023] [Accepted: 07/10/2023] [Indexed: 10/21/2023]
Abstract
Loa loa, the African eye worm, is a filarial pathogen transmitted by blood-sucking flies of the genus Chrysops. Loiasis primarily affects rural populations residing in the forest and adjacent savannah regions of central and west Africa, where more than 20 million patients are chronically infected in medium and high transmission regions. For a long time, loiasis has been regarded as a relatively benign condition. However, morbidity as measured by disability-adjusted life-years lost might be as high as 400 per 100 000 residents, and the population attributable fraction of death is estimated at 14·5% in highly endemic regions, providing unequivocal evidence for the substantial disease burden that loiasis exerts on affected communities. The clinical penetrance of loiasis is variable and might present with the classic signs of eye worm migration or transient Calabar swellings, but might include common, unspecific symptoms or rare but potentially life-threatening complications. Although adult worm migration seems most closely linked to symptomatic disease, high levels of microfilaraemia are associated with clinically important complications and death. Loiasis remains difficult to diagnose, treat, and control due to an absence of reliable point-of-care diagnostic assays, safe and efficacious drugs, and cost-effective prevention strategies. This Review summarises the major advances in our understanding of loiasis made over the past decade and highlights the many gaps that await to be addressed urgently.
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Affiliation(s)
- Michael Ramharter
- Department of Clinical Research, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany; Division of Tropical Medicine, I Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Centre de Recherche Médicale de Lambaréné, Lambaréné, Gabon; German Center for Infection Research, Partner Site Hamburg-Lübeck-Borstel-Riems, Hamburg, Germany.
| | | | - Ghyslain Mombo-Ngoma
- Department of Implementation Research, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany; Division of Tropical Medicine, I Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Centre de Recherche Médicale de Lambaréné, Lambaréné, Gabon; German Center for Infection Research, Partner Site Hamburg-Lübeck-Borstel-Riems, Hamburg, Germany
| | - Tamara Nordmann
- Department of Clinical Research, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany; Division of Tropical Medicine, I Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; German Center for Infection Research, Partner Site Hamburg-Lübeck-Borstel-Riems, Hamburg, Germany
| | - Saskia Dede Davi
- Department of Clinical Research, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany; Division of Tropical Medicine, I Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; German Center for Infection Research, Partner Site Hamburg-Lübeck-Borstel-Riems, Hamburg, Germany
| | - Rella Zoleko Manego
- Department of Clinical Research, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany; Division of Tropical Medicine, I Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Centre de Recherche Médicale de Lambaréné, Lambaréné, Gabon
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Colorimetric and Real-Time Loop-Mediated Isothermal Amplification (LAMP) for Detection of Loa loa DNA in Human Blood Samples. Diagnostics (Basel) 2022; 12:diagnostics12051079. [PMID: 35626235 PMCID: PMC9139441 DOI: 10.3390/diagnostics12051079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 04/22/2022] [Accepted: 04/23/2022] [Indexed: 02/04/2023] Open
Abstract
Loiasis, caused by the filarial nematode Loa loa, is endemic in Central and West Africa. Loa loa has been associated with severe adverse reactions in high Loa-infected individuals receiving ivermectin during mass drug administration programs for the control of onchocerciasis and lymphatic filariasis. Diagnosis of loiasis still depends on microscopy in blood samples, but this is not effective for large-scale surveys. New diagnostics methods for loiasis are urgently needed. Previously, we developed a colorimetric high-sensitive and species-specific LAMP for Loa loa DNA detection. Here, we evaluate it in a set of 100 field-collected clinical samples stored as dried blood spots. In addition, Loa loa-LAMP was also evaluated in real-time testing and compared with microscopy and a specific PCR/nested PCR. A simple saponin/Chelex-based method was used to extract DNA. Colorimetric and real-time LAMP assays detected more samples with microscopy-confirmed Loa loa and Loa loa/Mansonella perstans mixed infections than PCR/nested-PCR. Samples with the highest Loa loa microfilariae counts were amplified faster in real-time LAMP assays. Our Loa loa-LAMP could be a promising molecular tool for the easy, rapid and accurate screening of patients for loiasis in endemic areas with low-resource settings. The real-time testing (feasible in a handheld device) could be very useful to rule out high-microfilariae loads in infected patients.
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