الفهرس 
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Abstract
The present study was performed to evaluate different seroological tests namely, indirect fluorescent antibody test (I~AT), enzyme-linked immunosorbent assay (ELISA) and gel diffusion (GD) for diagnosis of giardiasis in human cases.
The study was performed on 2100 patients attending the Outtpatient Clinics and Inpatient Sections of Abou El-Rlsh Hospital, Pac_lty of Medicine, Cairo University. For botb infected and conntrol cases, full sheets were prepared to obtain data including age, sex and duration of complaint. The age of the examined innfected cases and control ranged from six months up to 16 years. The duration of complaint ranged from one day up to J years.
from each case and control a stool sample was examined for Giardia cysts or trophozoites by direct smear method and zinc sulphate centrifugal floatation method. The intensity of infecction by Giardia was estimated. It ranged from 12.5 X 103 - 125 X 104 cysts/gm stool. Evaluation of the relation between intensity of infection and age & sex of patients and duration of complaint was attempted. The ~esultB showed no significant relations.
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Assessment of anti-Giardia antibodies in the infected patients and control was evaluated by IFAT, ELISA and GD.
Intact Giardia cysts were used as antigen for IFAT, While sonicated cysts were used for both ELISA and GD. The sensitiivity of IFAT (IgG & IgM), ELISA (IgG) and GD was 66.4%, ~4.1%, 52.7% and 8.6% respectively, While the specificity was 80% , 94%, 84% and 98% respectively. Evaluation of the three seroloogical teats as regards age & sex of patients, duration of commplaint and intensity of infection was studied.
Regarding age, it was found that ELISA (IgG) detected siggnificantly higher (P<O.050) percentages of positive cases (44.4%) among patients aged «4 years than other tests. On the other hand, IFAT (IgG) detected significantly (P~O.050) higher percentages (68.9% and 79%) of positive cases among patients aged 4 - 10 and > 10 years respectively.
Regarding sex, it was found that in both sexes higher perrcentage of positive cases (66.4% and 63.3%) were detected by IFAT (IgG) than by ELISA, while GD detected the least number of cases. The results were statistically significant (p ~O.050).
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It was found that IFAT (IgG) detected insignificantly higher (F ~O.50) percentages of positive cases at different durations of infections (60.5%, 78.4%, 67.5%, 66.~ and 66.7%),
while GD detected the least number of positive cases.
Results of the three serological tests in relation to inntensity of infection showed that at all intensities, IFAT (IgG) detected significantly (P ~O.050) higher percentages of posiitive cases (44.1%, 13.3% and 92.5%) than ELISA. It was also found that in all tests the percentage of detected positive cases increased significantly with increasing intensity of innfection.
Concerning the results of the three serological tests in Giardia infected patients with both single and mixed infection, it was found that IFAT (IgG) detected significantly higher
(F 0.50) percentages Of positive cases with single (69.4%) and mixed (61.6%) giardiasis, while ELISA (IgG) and GD detected significantly higher (P <0.50) percentages of positive cases (56.9% and 10.5%) with mixed infection.
In Case of mixed infection with different intestinal paraasites, it was found that IFAT (IgG & IgM) showed insignificantly
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high (F > 0.050) titres with Taenia ap. infection. ELISA (IgG)
also showed insignificantly high (F > 0.050) titres with Ascaris
and Taenia sp.
The presence of anti-Giardia antibodies in abnormal control cases was insignificantly (P> 0.050) with moderate titrea in
cases of infection with S. mansoni screened by IFAT (IgG) and
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with Oxyuris and A. ,•du.odenale screened by IFAT (IgM).
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Conclusion:
from the present study, it could be conclUded that Giardia
lamblia infection is rather prevalent especially among young
aged patients. It was found that the intensity of infection
with Q. lamblia could not be correlated with either age, sex or
duration of infection of the patient.
Diagnosis of Q. lamblia by direct methods is often difficult.
On the other hand, indirect methods of diagnosis were not en-
courging as the sensitivity of the three serological tests was
mostly low. Further trials to improve the quality of the anti-
gen by using the trophozoites or different Giardia strains
should be considered. However, IFAT (IgG) proved to be the most sensitive test, while GD the most speciric one.
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Fatients aged 4 - 1U years showed highest infection rate.
Accordingly studying anti-Giardi~ antibodies may be more feasiible in this age group. Sex of patients should not be considered as an important determining factor in the concept of serodiag-
nosis of giardiasis.
Persistant elevation of IgG at different durations of innfection with Giardia ahould be anticipated as in endemic areas, like Egypt, repeated Giardl~ infection is often frequent.
Anti-G1ardia IgG antibodies rise steadily with the increase in intensity of infection, especially if screened by IFAT.
Mixed intestinal infection did not significantly raise the anti-Giardia antibodies. The apparent cross reactiVity of Giardd~ antigen with other parasitic infections in cases not passing Giardia cysts or trophozoites in their stools may be due to the persistance of anti-giardia antibodies in the absence of intesstinal stages of the parasite eleminated by therapy or selt cure.
from the practical point of view, IFAT was relatively easier to perform than the other two tests •