Related Experiment Video
Updated: May 23, 2026
Comparative Analysis of Automatic Fecal Analyzer versus Direct Wet Smear Microscopy for Detecting Parasitic Infections in Stool Samples
Published on: April 25, 2025
Laboratory diagnosis for Giardia lamblia infection: A comparison of microscopy, coprodiagnosis and serology
M A Behr1, E Kokoskin, T W Gyorkos
1McGill University Centre for Tropical Diseases; Division of Clinical Epidemiology, Montreal General Hospital; and Institute of Parasitology, McGill University, Montreal, Quebec.
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.
