Last update:
   07-Jul-2004
 

Arch Hellen Med, 20(3), May-June 2003, 299-304

ORIGINAL PAPER

Evaluation of two enzyme-linked immunosorbent assays
and one immunochromatographic rapid assay
for the detection of Giardia lamblia-specific antigens
in fecal specimens of patients with giardiasis

K. TZANETOU, E. DOLAPSAKI, C. KAKARI, A. SIDERI, A. BLACHAKI, E. MICHAELIDOU,
A. TSOUKNIDA, S. POLITAKI, A. TSANTES, V. PAPAIOANOU, G. MITSAKOU, E. MALAMOU-LADA
Laboratory of Microbiology, “G. Gennimatas” District General Hospital of Athens, Athens, Greece

OBJECTIVE The estimation of the sensitivity and specificity of two enzyme immunoassays (Alexon-Trend ProSpecT Giardia Microplate Assay and Cypress Diagnostics Giardiasis Ag ELISA) and one immunochromatographic assay (Becton Dickinson ColorPAC Giardia/Cryptosporidium Rapid Assay) in comparison with microscopic detection of Giardia cysts and trophozoites in the patients’ fecal specimens, in order to evaluate their usefulness as alternative methods for diagnosing giardiasis.

METHOD During the last 2.5 years, 5,800 fecal specimens were examined by conventional microscopic examination (direct wet preparation and after concentration) for ova and parasites. All the fecal specimens positive for cysts and/or trophozoites of Giardia using the ova and parasite examination were stored fresh (unpreserved) at -70 °C. These fecal specimens were examined retrospectively for the presence of Giardia specific antigens by the 3 methods mentioned above, using the manufacturers’ recommended procedures. In addition 52 fecal specimens negative for Giardia by ova and parasite examination were tested.

RESULTS Sixty one fecal specimens (29 from Greek patients and 32 from immigrants) of the 5,800 examined were found positive for Giardia by microscopic examination (1.05%). Giardia Specific Antigen 65 (GSA 65) was detected in all the 61 positive fecal specimens tested by Alexon ProSpecT Giardia Microplate Assay (sensitivity 100%). Two fecal specimens of the 61 (with the lowest absorptions in the Alexon-Trend assay) were found negative tested by the immunochromatographic assay (sensitivity 96.72%), and one also when by the Cypress diagnostic kit (sensitivity 98.36%). The 52 negative samples tested negative in all diagnostic kits (specificity 100%).

CONCLUSIONS (a) ProSpecT Giardia Microplate Assay, which is as sensitive and specific as the microscopic detection of the parasite and secondly Giardiasis Ag ELISA (Cypress Diagnostics) offer alternative or complementary methods to the routine ova and parasite examination, especially in the case of chronic diarrhea or clinical suspicion of giardiasis, when the first microscopic examination of the stool is negative. (b) The ColorPAC Giardia/Cryptosporidium Rapid Assay could be applied as a rapid screening test, though a negative result does not firmly exclude the infection.

Key words: Enzyme immunoassay, Giardia specific antigens, Giardiasis, Immunochromatographic assay.

© Archives of Hellenic Medicine