Efficiency of Direct Microscopy of Stool Samples Using an Antigen-Specific Adhesin Test for Entamoeba Histolytica.

BACKGROUND

is among the common causes of acute gastroenteritis. The pathogenic species and the nonpathogenic species cannot be morphologically differentiated, although correct identification of these protozoans is important for treatment and public health. In many laboratories, the screening of leukocytes, erythrocytes, amoebic cysts, trophozoites and parasite eggs is performed using Native-Lugol's iodine for pre-diagnosis.

AIMS

In this study, we aimed to investigate the frequency of in stool samples collected from 788 patients residing in the Anatolian region of İstanbul who presented with gastrointestinal complaints. We used the information obtained to evaluate the effectiveness of microscopic examinations when used in combination with the adhesin antigen test.

STUDY DESIGN

Retrospective cross-sectional study.

METHODS

Preparations of stool samples stained with Native-Lugol's iodine were evaluated using the adhesin test and examined using standard light microscopy at ×40 magnification. Pearson's Chi-square and Fisher's exact tests were used for statistical analysis. Logistic regression analysis was used for multivariate analysis.

RESULTS

Of 788 samples, 38 (4.8%) were positive for adhesin antigens. When evaluated together with the presences of erythrocytes, leukocytes, cysts, and trophozoites, respectively, using logistic regression analysis, leukocyte positivity was significantly higher. The odds ratio of leukocyte positivity increased adhesin test-positivity by 2,530-fold (95% CI=1.01-6.330). Adhesin test-positivity was significant (p=0.047).

CONCLUSION

In line with these findings, the consistency between the presence of cysts and erythrocytes and adhesin test-positivity was found to be highly significant, but that of higher levels of leukocytes was found to be discordant. It was concluded that leukocytes and trophozoites were easily misjudged using direct microscopy. Although microscopic examination of samples stained with Native-Lugol's iodine is a cheap and simple method, the confusion of trophozoites with leukocytes may direct the clinician toward an incorrect pre-diagnosis. Because trichrome staining is difficult and time consuming, and results may vary depending on the technician, this method is not preferred in most laboratories. Therefore, an enzyme-linked immunosorbent assay method, which is a more advanced method than polymerase chain reaction, should be used to distinguish between and in order to achieve an accurate diagnosis.