Detection of Intestinal Parasites in Diarrhea Samples Using Various Diagnostic Methods and Evaluation of the Stability of In-house Quality Control Materials for Stool Examination

ABSTRACT

BACKGROUND: Because of a lack of quality control (QC) materials, stool examination has not been standardised. This study examined intestinal parasites in diarrhea specimens to manufacture and evaluate the performance stability of QC materials for stool examination. METHODS: This study examined diarrhea specimens submitted for stool culture. Microscopic examination was performed using the direct smear and formalin-ether concentration method (Military General Laboratory, MGL). Enzyme-linked immunosorbent assay (ELISA) kits (R-Biopharm AG, Germany) and xTAG Gastrointestinal Pathogen Panel (Luminex Corp., USA) were used for the three major protozoa Cryptosporidium parvum, Giardia lamblia, and Entamoeba histolytica. Polymerase chain reaction (PCR) was performed for Dientamoeba fragilis and Blastocystis hominis. The QC materials for stool examination were generated using Diphyllobothrium nihonkaiense ova. The manufactured QC materials were evaluated under different storage conditions, with varying preservatives, temperatures, and storage times. RESULTS: From November 2015 to April 2016, 82 diarrhea specimens were collected and tested. All results from microscopy and ELISA were negative; C. parvum (n=2) and G. lamblia (n=1) were detected by xTAG, while D. fragilis (n=10) and B. hominis (n=2) were detected by PCR. High- and low-concentration QC materials were manufactured. Using the high-concentration QC material, ova were observed in all storage conditions using MGL. Using the low-concentration QC material, the ova were observed until 14 days, but not after 3 weeks. CONCLUSIONS: It should be considered for making QC materials for stool examinations that focus on D. fragilis and B. hominis frequently found in Korea and with the caution to the low-concentration of QC materials could be unstable.