title: Strongyloidiasis in Ontario: Performance of diagnostic tests over a 14-month period.
abstract: BACKGROUND
  We evaluated the performance of stool microscopy, serology, and real time PCR (qPCR) for the diagnosis of strongyloidiasis at our reference laboratory.
  
  
  METHODS
  Using a convenience sample of specimens submitted between April 1, 2014 and May 31, 2015, positivity rates and performance characteristics were calculated.
  
  
  RESULTS
  During the enrolment period, 17,933 stool specimens were examined for O&P, 14 of which were positive for Strongyloides larvae. For stool specimens serially positive for larvae, mean duration of larval shedding was 12.7 days following the initial positive specimen, while for sputum and urine, it was 12 and 2 days, respectively. During the enrolment period, 3258 specimens were processed for Strongyloides serology, 200 of which were reactive (6.1%), 210 indeterminate (6.5%), and 2848 non-reactive (87.4%). qPCR was positive in 11 of 12 (91.7%) stool specimens containing larvae, and negative in all stool specimens without larvae by microscopy. There was no cross-reactivity of Strongyloides-specific qPCR to other stool protozoa or helminths.
  
  
  CONCLUSIONS
  In the absence of immunosuppression, larval burden in strongyloidiasis is low, limiting the utility of microscopy, and favoring serologic testing. However, false negative serology can occur in those with hyperinfection necessitating a combined diagnostic approach. qPCR was insufficiently sensitive to replace microscopy for detection of larvae.
authors: University of Western Ontario, London, Ontario, Canada.
authors: Michelle Dao
authors: MD
authors: Dong
authors: Faculty of Arts and Sciences, University of Toronto, Canada.
authors: Nessika
authors: N
authors: Karsenti
authors: Public Health Ontario Laboratories, Public Health Ontario, Toronto, Ontario, Canada.
authors: Rachel
authors: R
authors: Lau
authors: Public Health Ontario Laboratories, Public Health Ontario, Toronto, Ontario, Canada.
authors: Filip
authors: F
authors: Ralevski
authors: Public Health Ontario Laboratories, Public Health Ontario, Toronto, Ontario, Canada.
authors: Karamjit
authors: K
authors: Cheema
authors: Public Health Ontario Laboratories, Public Health Ontario, Toronto, Ontario, Canada.
authors: Laura
authors: L
authors: Burton
authors: McMaster University, Hamilton, Ontario, Canada.
authors: Michael
authors: M
authors: Klowak
authors: Public Health Ontario Laboratories, Public Health Ontario, Toronto, Ontario, Canada; Tropical Disease Unit, Toronto General Hospital, Toronto, Ontario, Canada; Department of Medicine, University of Toronto, Ontario, Canada. Electronic address: andrea.boggild@utoronto.ca.
authors: Andrea K
authors: AK
authors: Boggild
mesh_terms: D000818:Animals; D005243:Feces / Q000469:parasitology*; D006801:Humans; D007814:Larva / Q000235:genetics / Q000648:ultrastructure; D008853:Microscopy; D058069:Neglected Diseases / Q000175:diagnosis / Q000469:parasitology; D009864:Ontario / Q000453:epidemiology; D059208:Parasite Load; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D013183:Sputum / Q000469:parasitology; D013321:Strongyloides / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification* / Q000648:ultrastructure; D013322:Strongyloidiasis / Q000175:diagnosis* / Q000453:epidemiology* / Q000469:parasitology; D014556:Urine / Q000469:parasitology
keywords: Disseminated strongyloidiasis; Neglected tropical diseases; Serology; Soil-transmitted helminths; Stool microscopy