الفهرس 
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Abstract
an infection by the protozoan parasite E. histolytica, is globally considered as the third leading parasitic cause of human mortality besides malaria and schistosomiasis. It is estimated that E. histolytica may infect half a billion people annually. Moreover, it was estimated that 50,000 -100,000 patients per year died due to the clinical complications of the disease.
Laboratory diagnosis of E. histolytica/dispar is usually achieved by microscopic detection of trophozoites or cysts in stool samples. Microscopy is time-consuming and requires an experienced observer to identify the organism. Furthermore, it may be performed on three stool samples collected every other day over not more than 10 days to increase the sensitivity leading to decreased patient compliance and delay in the final diagnosis.
Therefore, a few commercially available copro-antigen assays have been developed for E. histolytica/dispar diagnosis including the enzyme immunoassay and non-enzymatic immunochromatographic (ICT) assays that do not depend on microscopy skills and increase laboratory efficiency by reducing time.
This study aimed to evaluate the efficacy of commercially available rapid immunochromatographic Copro-antigen assay (RIDA®QUICK Entamoeba, R-Biopharm AG, Darmstadt, Germany) in comparison with conventional microscopic examination for the diagnosis of E. histolytica/dispar infection. In addition, to estimate the prevalence of E. histolytica /dispar infection in outpatients in Sohag.
100 stool samples were collected from patients complaining of dysentery or diarrhea with age ranging from 3 to 62 years (Mean ± SD = 20.44 ± 1.61), attending outpatient clinics in Sohag University Hospitals and Endemic Diseases Hospital. They had to fulfill the criteria: not taking amoebicidal drugs two weeks before sample collection.
All samples were examined by microscopic examination including direct mount, formalin ethyl-acetate sedimentation concentration technique, Wiegert’s iron hematoxylin staining & ICT (Rida® Quick Entamoeba cassettes; R-Biopharm, Germany).
In this study, microscopic examination of stained smears was considered the gold standard to which results of Rida®Quick Entamoeba cassettes were compared.
In the present study, microscopic examination revealed E. histolytica/dispar (43%). The results showed that the sensitivity and specificity of Rida®Quick Entamoeba test were (97.67%) and (96.49%) respectively, with no cross-reactivity with other parasites copro-antigen. Moreover, the Kappa value was 0.939, which means the perfect agreement between both diagnostic methods.
The observed advantages of the Rida®Quick Entamoeba test were that it did not require any microscope, centrifugation, staining, or experienced personnel and was rapid; only required 10 minutes to be performed. So, it can be used to yield rapid results, for outbreak situations, screening proposals, and massive assays in endemic areas where a large number of samples must be analyzed. Whereas its main disadvantage was its high cost.
The causes of limitations of this study were the small sample size because of cost, and the tests employed for the diagnosis of E. histolytica/dispar did not include more accurate methods such as PCR.
Moreover, failure to differentiate between E. hitolytica & E.dispar species might be a missed opportunity to better elucidate the findings in a way to offer input towards continuous improvement of the rapid tests. Also, quantitative ICT models are required to measure the intensity of infection and monitor therapeutic success.
CONCLUSION
The present results revealed that microscopy is still the preferred method for diagnosing E. histolytica/dispar; being more sensitive, of low cost and it allows detection of other intestinal parasites in the sample if present.
Also, we found that the Rida®Quick Entamoeba test is simple, rapid, and has adequate sensitivity and specificity. Moreover, it does not require experienced personnel or special technical equipment. So, it can be used as an alternative test in certain situations where the microscopic diagnosis of E. histolytica/dispar is limited due to time restriction, lack of microscopy experts, unavailability of appropriate equipment or when examining large groups as in outbreaks and epidemiological surveys.
Unfortunately, the Rida®Quick Entamoeba test has the disadvantages of high cost, inability to differentiate between the pathogenic and non-pathogenic E. histolytica and E. dispar respectively. Moreover, quantitative ICT models are required to measure the intensity of infection and monitor therapeutic success.
RECOMMENDATIONS
In the present study, microscopy was the ”gold standard” for the evaluation of the sensitivity and specificity of Rida®Quick Entamoeba.
We recommend further studies to be performed using a more accurate diagnostic method as PCR to be the ”gold standard”.
We recommend genotyping in further studies for the false-negative samples to offer input towards the continuous improvement of the rapid tests & to differentiate between the pathogenic and non-pathogenic E. histolytica and E. dispar respectively for better epidemiological studies & treatment requirements.