Comparison of Three Parasitological Stool Examination Methods with the Formalin-Ethyl Acetate Procedure for the Diagnosis of Intestinal Parasites in Humans

Abstract

Aims: The objective was to compare the sedimentation spontaneous in tube technique (SSTT), the direct smear, the zinc sulfhate (surface film and sediment analyzed) methods with the formalin-ethyl acetate method as the reference standard. Study Design: This a cross-sectional study performed in two populations around Chapala lake, Jalisco, Mexico. Place and Duration of Study: Sample Department of Medical Sciences and Life, University Center of the Ciénega, University of Guadalajara, Ocotlán, Jalisco, Mexico. Department of Physiology, Health Sciences University Center. University of Guadalajara, Jalisco. México, between June 2018 and July 2019. Methodology: Sample: We included a total of 297 samples and were analyzed by the direct smear, the zinc sulfhate (surface film and sediment analyzed), the SSTT and formalin-ethyl acetate methods. Results: The SSTT was able to detect 40% of intestinal parasites, very good agreement for Entamoeba complex, Entamoeba coli, and Ascaris lumbricoides kappa index=0.697, 0.791, 0.696, respectively and excellent agreement for Giardia lamblia kappa index = 0.843. Regarding the isolation of Blastocystis spp, only a poor agreement was found among all techniques. The SSTT was able to detect multiple parasites with a sensitivity of 82.90% and specificity 83.80 kappa index= 0.649. Conclusion: The SSTT showed a very good agreement for the diagnosis intestinal polyparasitism which could represent another alternative for the concentration and identification protozoans and intestinal helminthes in low-resource settings.