Immunofluorescence Assay and PCR Analysis of Cryptosporidium Oocysts and Species From Human Feacal Specimens

BACKGROUND: Cryptosporidium spp. is a widespread protozoan parasite involving humans and animals. OBJECTIVES: This study was carried out to evaluate the immunofluorescence assay (IFA) and PCR results for more accurate diagnosis of faecal specimens. PATIENTS AND METHODS: Forty six faecal human specimens of Cryptosporidium oocysts were examined by PCR and IFA in Calgary, Canada. In statistical analysis, sensitivity and positive predictive value were detected by IFA. RESULTS: Among 46 faecal samples, 9 (19.6%) were IFA-positive and 10 (21.7%) PCR-positive. Faecal smears of both PCR- and IFA-positive shown that the reproducibility was 90.9% for PCR-DNA and 81.8% for IFA. In Our findings, PCR -DNA showed that diagnosis cryptosporidiosis 2.1% was more sensitive than IFA. Two different oocysts sizes were visualized by IF microscopy which belonged to different species. Furthermore, PCR analysis with primers against the 18S rRNA gene indicated two genotypes of C. hominis and C. parvum, 500-650 base pairs (bp). In this study, the golden standard was the PCR. In statistical analyses, IFA had positive predictive value (PPV) of 81.8% with 81.8% sensitivity, whereas negative predictive value (NPV) was 1% with 0.97% specificity. CONCLUSIONS: PCR showed more sensitivity than IFA for tracking Cryptosporidium oocysts as well as detection of species in faecal human specimens.