Preliminary Study on PCR Method for Laboratory Diagnosis with Fecal Specimens of Entamoeba histolytica Infection

  Objective  To develop a PCR method for Entamoeba histolytica（E.histolytica) detection in fecal specimens, and to compare the performance of PCR to that of microscopy and ELISA.

  Methods  Two pairs of self-designed primers and 2 pairs of primers from references based on small subunit ribosome RNA (SSU rRNA) fragment of E. histolytica standard strain were synthetized. DNA from E. histolytica reference strain were amilified by the conventional PCR using the 4 pairs of primers. 221 stool samples from diarrhea patients were collected and detected for E. histolytica by three methods: Entamoeba trophozoites and cysts detection by microscopy, E. histolytica-specific antigen detection using enzyme-linked immunosorbent assay (ELISA) kit (E. HISTOLYTICA II), amplification of SSU rRNA fragment of E. histolytica by PCR method. Positive rate of three methods were compared by chi-square test, and Kappa test was applied to determine the concordance among the three methods.

  Results  Specific fragments of E. histolytica were amplified by the PCR method we developed in this study. Positive rates of PCR, microscopy and ELISA were 2.26%, 0.90% and 9.50%, respectively. The positive rates of the three methods were significantly different (χ²=23.34, P<0.01). The Kappa value of PCR and microscopy was 0.216, and that of PCR and ELISA method was –0.134, both of which showed a weak consistency. PCR results showed best consistency with clinical diagnosis.

  Conclusion  The PCR method we established in this study has a better performance in accuracy than microscopy and ELISA have in laboratory diagnosis of E. histolytica infection.