title: Loss of sensitivity of immunochromatographic test (ICT) for lymphatic filariasis diagnosis in low prevalence settings: consequence in the monitoring and evaluation procedures.
abstract: BACKGROUND
  Diagnostic tools for lymphatic filariasis (LF) elimination programs are useful in mapping the distribution of the disease, delineating areas where mass drug administrations (MDA) are required, and determining when to stop MDA. The prevalence and burden of LF have been drastically reduced following mass treatments, and the evaluation of the performance of circulating filarial antigen (CFA)-based assays was acknowledged to be of high interest in areas with low residual LF endemicity rates after multiple rounds of MDA. The objective of this study was therefore to evaluate the immunochromatographic test (ICT) sensitivity in low endemicity settings and, specifically, in individuals with low intensity of lymphatic filariasis infection.
  
  
  METHODS
  To perform this study, calibrated thick blood smears, ICT and Og4C3 enzyme-linked immunosorbent assay (ELISA) were carried out by night to identify Wuchereria bancrofti microfilarial and circulating filarial antigen carriers. A threshold determination assay regarding ICT and ELISA was performed using serial plasma dilutions from individuals with positive microfilarial counts.
  
  
  RESULTS
  All individuals harbouring microfilariae (positive blood films) were detected by ICT and ELISA, but among individuals positive for ELISA, only 35.7 % of them were detected using ICT (Chi square: 4.57; p-value = 0.03), indicating a moderate agreement between both tests (kappa statistics = 0.49). Threshold determination analyses showed that ELISA was still positive at the last plasma dilution with negative ICT result.
  
  
  CONCLUSIONS
  These findings suggest a loss of sensitivity for ICT in low endemicity settings, especially in people exhibiting low levels of circulating filarial antigen, raising serious concern regarding the monitoring and evaluation procedures in the framework of LF elimination program.
authors.affiliation: Centre for Research on Filariasis and other Tropical Diseases (CRFilMT), P.O. Box 5797, Yaounde, Cameroon. gounoue@crfilmt.org.|Department of Animal Biology and Physiology, Laboratory of Animal Physiology, Faculty of Science, University of Yaounde 1, P.O. Box 812, Yaounde, Cameroon. gounoue@crfilmt.org.
authors.forename: Raceline
authors.initials: R
authors.lastname: Gounoue-Kamkumo
authors.affiliation: Centre for Research on Filariasis and other Tropical Diseases (CRFilMT), P.O. Box 5797, Yaounde, Cameroon. nanadjeunga@crfilmt.org.|Department of Animal Biology and Physiology, Parasitology and Ecology Laboratory, Faculty of Science, University of Yaounde 1, P.O. Box 812, Yaounde, Cameroon. nanadjeunga@crfilmt.org.
authors.forename: Hugues C
authors.initials: HC
authors.lastname: Nana-Djeunga
authors.affiliation: Centre for Research on Filariasis and other Tropical Diseases (CRFilMT), P.O. Box 5797, Yaounde, Cameroon. bopda@crfilmt.org.
authors.forename: Jean
authors.initials: J
authors.lastname: Bopda
authors.affiliation: Helen Keller International, P.O. Box 14227, Yaounde, Cameroon. jakame@hki.org.
authors.forename: Julie
authors.initials: J
authors.lastname: Akame
authors.affiliation: Helen Keller International, P.O. Box 14227, Yaounde, Cameroon. tariniann@gmail.com.
authors.forename: Ann
authors.initials: A
authors.lastname: Tarini
authors.affiliation: Centre for Research on Filariasis and other Tropical Diseases (CRFilMT), P.O. Box 5797, Yaounde, Cameroon. kamgno@crfilmt.org.|Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, P.O. Box 1364, Yaounde, Cameroon. kamgno@crfilmt.org.
authors.forename: Joseph
authors.initials: J
authors.lastname: Kamgno
mesh_terms: D000818:Animals; D000947:Antigens, Helminth / Q000097:blood* / Q000276:immunology; D002163:Cameroon / Q000453:epidemiology; D004605:Elephantiasis, Filarial / Q000175:diagnosis* / Q000453:epidemiology / Q000517:prevention & control; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008297:Male; D012680:Sensitivity and Specificity; D014958:Wuchereria bancrofti / Q000276:immunology / Q000472:pathogenicity
chemical_list: D000947:Antigens, Helminth