Xavier Martiáñez-Vendrell1, Alfons Jiménez1,2, Ana Vásquez3, Ana Campillo4, Sandra Incardona4, Raquel González1,2,5, Dionicia Gamboa6, Katherine Torres7, Wellington Oyibo8, Babacar Faye9, Eusebio Macete5, Clara Menéndez1,2,5, Xavier C Ding4, Alfredo Mayor10,11,12. 1. ISGlobal, Hospital Clínic of Barcelona, Universitat de Barcelona, Carrer Rosselló 153 (CEK building), 08036, Barcelona, Spain. 2. Spanish Consortium for Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain. 3. Grupo Malaria, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia. 4. FIND, Geneva, Switzerland. 5. Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique. 6. Departamento de Ciencias Celulares y Moleculares, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru. 7. Laboratorio de Malaria, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofia, Universidad Peruana Cayetano Heredia, Lima, Peru. 8. ANDI Centre of Excellence for Malaria Diagnosis, College of Medicine, University of Lagos, Idi-Aaraba, Lagos, Nigeria. 9. Service de Parasitologie-Mycologie, Faculté de Médecine, Pharmacie et Odontologie, Université Cheikh Anta Diop de Dakar, Dakar, Sénégal. 10. ISGlobal, Hospital Clínic of Barcelona, Universitat de Barcelona, Carrer Rosselló 153 (CEK building), 08036, Barcelona, Spain. alfredo.mayor@isglobal.org. 11. Spanish Consortium for Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain. alfredo.mayor@isglobal.org. 12. Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique. alfredo.mayor@isglobal.org.
Abstract
BACKGROUND: Malaria diagnostics by rapid diagnostic test (RDT) relies primarily on the qualitative detection of Plasmodium falciparum histidine-rich protein 2 (PfHRP2) and Plasmodium spp lactate dehydrogenase (pLDH). As novel RDTs with increased sensitivity are being developed and implemented as point of care diagnostics, highly sensitive laboratory-based assays are needed for evaluating RDT performance. Here, a quantitative suspension array technology (qSAT) was developed, validated and applied for the simultaneous detection of PfHRP2 and pLDH in a variety of biological samples (whole blood, plasma and dried blood spots) from individuals living in different endemic countries. RESULTS: The qSAT was specific for the target antigens, with analytical ranges of 6.8 to 762.8 pg/ml for PfHRP2 and 78.1 to 17076.6 pg/ml for P. falciparum LDH (Pf-LDH). The assay detected Plasmodium vivax LDH (Pv-LDH) at a lower sensitivity than Pf-LDH (analytical range of 1093.20 to 187288.5 pg/ml). Both PfHRP2 and pLDH levels determined using the qSAT showed to positively correlate with parasite densities determined by quantitative PCR (Spearman r = 0.59 and 0.75, respectively) as well as microscopy (Spearman r = 0.40 and 0.75, respectively), suggesting the assay to be a good predictor of parasite density. CONCLUSION: This immunoassay can be used as a reference test for the detection and quantification of PfHRP2 and pLDH, and could serve for external validation of RDT performance, to determine antigen persistence after parasite clearance, as well as a complementary tool to assess malaria burden in endemic settings.
BACKGROUND:Malaria diagnostics by rapid diagnostic test (RDT) relies primarily on the qualitative detection of Plasmodium falciparumhistidine-rich protein 2 (PfHRP2) and Plasmodium spp lactate dehydrogenase (pLDH). As novel RDTs with increased sensitivity are being developed and implemented as point of care diagnostics, highly sensitive laboratory-based assays are needed for evaluating RDT performance. Here, a quantitative suspension array technology (qSAT) was developed, validated and applied for the simultaneous detection of PfHRP2 and pLDH in a variety of biological samples (whole blood, plasma and dried blood spots) from individuals living in different endemic countries. RESULTS: The qSAT was specific for the target antigens, with analytical ranges of 6.8 to 762.8 pg/ml for PfHRP2 and 78.1 to 17076.6 pg/ml for P. falciparum LDH (Pf-LDH). The assay detected Plasmodium vivax LDH (Pv-LDH) at a lower sensitivity than Pf-LDH (analytical range of 1093.20 to 187288.5 pg/ml). Both PfHRP2 and pLDH levels determined using the qSAT showed to positively correlate with parasite densities determined by quantitative PCR (Spearman r = 0.59 and 0.75, respectively) as well as microscopy (Spearman r = 0.40 and 0.75, respectively), suggesting the assay to be a good predictor of parasite density. CONCLUSION: This immunoassay can be used as a reference test for the detection and quantification of PfHRP2 and pLDH, and could serve for external validation of RDT performance, to determine antigen persistence after parasite clearance, as well as a complementary tool to assess malaria burden in endemic settings.
Entities:
Keywords:
Histidine-rich protein 2; Luminex; Malaria; Parasite lactate dehydrogenase; Quantitative suspension array technology; Rapid diagnostic test