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Canadian Journal of Infectious Diseases
Volume 8, Issue 1, Pages 33-38
Original Article

Laboratory Diagnosis for Giardia Lamblia Infection: A Comparison of Microscopy, Coprodiagnosis and Serology

Marcel A Behr,1,2 Evelyne Kokoskin,1 Theresa W Gyorkos,1,2,3 Lyne Cédilotte,1 Gaetan M Faubert,1,3 and J Dick MacLean1,2

1McGill University Centre for Tropical Diseases, Canada
2Division of Clinical Epidemiology, Montreal General Hospital, Canada
3Institute of Parasitology, McGill University, Montreal, Quebec, Canada

Received 14 February 1996; Accepted 15 July 1996

Copyright © 1997 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


OBJECTIVE: To evaluate newer techniques such as coproantigen detection and serology in the diagnosis of symptomatic Giardia lamblia infection.

DESIGN: 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.

SETTING: Travel medicine clinic.

POPULATION STUDIED: Adults, post-travel, with gastrointestinal symptomatology.

MAIN 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.