title: Real-time PCR for detection of Strongyloides stercoralis in human stool samples from Côte d'Ivoire: diagnostic accuracy, inter-laboratory comparison and patterns of hookworm co-infection.
abstract: Human infections with the helminth species Strongyloides stercoralis encompass a wide clinical spectrum, ranging from asymptomatic carriage to life-threatening disease. The diagnosis of S. stercoralis is cumbersome and the sensitivity of conventional stool microscopy is low. New molecular tools have been developed to increase sensitivity. We compared the diagnostic accuracy of real-time PCR with microscopy for the detection of S. stercoralis and hookworm in human stool samples, and investigated the inter-laboratory agreement of S. stercoralis-specific real-time PCR in two European laboratories. Stool specimens from 256 randomly selected individuals in rural Côte d'Ivoire were examined using three microscopic techniques (i.e. Kato-Katz, Koga agar plate (KAP) and Baermann (BM)). Additionally, ethanol-fixed stool aliquots were subjected to molecular diagnosis. The prevalence of S. stercoralis and hookworm infection was 21.9% and 52.0%, respectively, whilst co-infections were detected in 35 (13.7%) participants. The diagnostic agreement between real-time PCR and microscopy was excellent when both KAP and BM tested positive for S. stercoralis, but was considerably lower when only one microscopic technique was positive. The sensitivity of KAP, BM and real-time PCR for detection of S. stercoralis as compared to a combination of all diagnostic techniques was 21.4%, 37.5% and 76.8%, respectively. The inter-laboratory agreement of S. stercoralis-specific PCR was substantial (κ=0.63, p<0.001). We conclude that a combination of real-time PCR and stool microscopy shows high accuracy for S. stercoralis diagnosis. Besides high sensitivity, PCR may also enhance specificity by reducing microscopic misdiagnosis of morphologically similar helminth larvae (i.e. hookworm and S. stercoralis) in settings where both helminth species co-exist.
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland; University of Basel, P.O. Box, CH-4003 Basel, Switzerland; Institute of Medical Microbiology and Hygiene, Saarland University, Kirrberger Straße, Building 43, D-66421 Homburg/Saar, Germany.
authors.forename: Sören L
authors.initials: SL
authors.lastname: Becker
authors.affiliation: Institute of Medical Microbiology and Hygiene, Saarland University, Kirrberger Straße, Building 43, D-66421 Homburg/Saar, Germany.
authors.forename: Nivetha
authors.initials: N
authors.lastname: Piraisoody
authors.affiliation: University of Basel, P.O. Box, CH-4003 Basel, Switzerland; Department of Medical Services and Diagnostics, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Kramme
authors.affiliation: University of Basel, P.O. Box, CH-4003 Basel, Switzerland; Department of Medical Services and Diagnostics, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland.
authors.forename: Hanspeter
authors.initials: H
authors.lastname: Marti
authors.affiliation: Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, 02 BP 770, Abidjan 02, Côte d'Ivoire; Département Environnement et Santé, Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire.
authors.forename: Kigbafori D
authors.initials: KD
authors.lastname: Silué
authors.affiliation: Institute of Virology, University Medical Center Freiburg, Hermann-Herder-Straße 11, D-79104 Freiburg, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Panning
authors.affiliation: University of Basel, P.O. Box, CH-4003 Basel, Switzerland; Department of Medical Services and Diagnostics, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Nickel
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University Medical Center Freiburg, Hugstetter Straße 55, D-79106 Freiburg, Germany.
authors.forename: Winfried V
authors.initials: WV
authors.lastname: Kern
authors.affiliation: Institute of Medical Microbiology and Hygiene, Saarland University, Kirrberger Straße, Building 43, D-66421 Homburg/Saar, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Herrmann
authors.affiliation: University of Basel, P.O. Box, CH-4003 Basel, Switzerland; Department of Medical Services and Diagnostics, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland; Epidemiology, Biostatistics and Prevention Institute, University of Zurich, P.O. Box, CH-8001 Zurich, Switzerland.
authors.forename: Christoph F
authors.initials: CF
authors.lastname: Hatz
authors.affiliation: Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, 02 BP 770, Abidjan 02, Côte d'Ivoire; Département Environnement et Santé, Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire.
authors.forename: Eliézer K
authors.initials: EK
authors.lastname: N'Goran
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland; University of Basel, P.O. Box, CH-4003 Basel, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Utzinger
authors.affiliation: Institute of Medical Microbiology and Hygiene, Saarland University, Kirrberger Straße, Building 43, D-66421 Homburg/Saar, Germany. Electronic address: lutz.mueller@christophorus-kliniken.de.
authors.forename: Lutz
authors.initials: L
authors.lastname: von Müller
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000723:Ancylostomatoidea / Q000235:genetics / Q000302:isolation & purification*; D000818:Animals; D002648:Child; D002675:Child, Preschool; D060085:Coinfection; D007560:Cote d'Ivoire / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005243:Feces / Q000469:parasitology; D005260:Female; D006725:Hookworm Infections / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D060888:Real-Time Polymerase Chain Reaction; D012424:Rural Population; D012680:Sensitivity and Specificity; D017171:Strongyloides stercoralis / Q000235:genetics / Q000302:isolation & purification*; D013322:Strongyloidiasis / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D055815:Young Adult
keywords: Baermann technique; Diagnostic accuracy; Hookworm; Koga agar plate culture; Real-time PCR; Strongyloides stercoralis