title: Laboratory diagnosis for Giardia lamblia infection: A comparison of microscopy, coprodiagnosis and serology.
abstract: OBJECTIVE
  To evaluate newer techniques such as coproantigen detection and serology in the diagnosis of symptomatic Giardia lamblia infection.
  
  
  METHODS
  Blinded comparison of copro-antigen detection (by ELISA), serology (immunoglobulin IgG and IgM anti-G lamblia by ELISA, and IgG, IgM and IgA by immunoblot) and microscopy in clinical samples. Microscopic findings for three preserved stools were considered the gold standard.
  
  
  METHODS
  Travel medicine clinic.
  
  
  METHODS
  Adults, post-travel, with gastrointestinal symptomatology.
  
  
  RESULTS
  For 152 previously collected stools, copro-antigen detection had a sensitivity of 73 of 74 (98.6%) and a specificity of 78 of 78 (100%). In clinical samples of 62 patients, eight of the 62 patients (13%) were diagnosed with G lamblia infection on microscopy. Copro-antigen diagnosis was accurate in symptomatic patients, with sensitivity of seven of eight (87.5%) and specificity of 52 of 54 (96.8%). Serology was less accurate. IgG response to G lamblia had sensitivity of four of seven and specificity of 24 of 50 (48%), and IgM response had sensitivity of three of six and specificity 27 of 48 (56%). Western blot had a sensitivity of five of seven and a specificity of 38 of 49 (78%).
  
  
  CONCLUSIONS
  Copro-antigen diagnosis of G lamblia is highly accurate in patients with chronic gastrointestinal complaints, while serology is less accurate and appears to be less useful diagnostically.
authors.affiliation: McGill University Centre for Tropical Diseases; Division of Clinical Epidemiology, Montreal General Hospital; and Institute of Parasitology, McGill University, Montreal, Quebec.
authors.forename: M A
authors.initials: MA
authors.lastname: Behr
authors.forename: E
authors.initials: E
authors.lastname: Kokoskin
authors.forename: T W
authors.initials: TW
authors.lastname: Gyorkos
authors.forename: L
authors.initials: L
authors.lastname: Cédilotte
authors.forename: G M
authors.initials: GM
authors.lastname: Faubert
authors.forename: J D
authors.initials: JD
authors.lastname: Maclean