Assessment of the ability of PCR for diagnosis of infection with Cryptosporidium in children with diarrhea

Usual diagnostic methods for detection of Cryptosporidium include smear preparation، modified Zeihl-Neelsen staining، microscopic examination and observation of oocysts. No studies have been done to compare PCR and Zeihl-Neelsen staining in Iran. This study was done to determine the positive predictive value، (PPV) and the negative predictive value (NPV) of PCR in comparison to modified Zeihl-Neelsen staining for isolation of Cryptosporidium in children with diarrhea.

Direct smears were prepared from fecal samples of 2500 children with diarrhea. Smears were stained by modified Zeihl-Neelsen method and examined by microscope. All samples positive for cryptosporidia and some randomized negative samples were selected for DNA extraction for PCR assay.

From 2500 fecal samples، 30 positive cases were detected by modified Zeihl-Neelsen، (Z-N) staining; these tested positive by PCR method too; however two samples، found to be negative on microscopic examination were positive by PCR technique. PPV and NPV of microscopic examination after staining with Z-N were computed as 94. 1% and 100%، PPV and NPV of PCR method were computed as 100%.

PCR is a sensitive technique for detection of Cryptosporidium، especially useful in immunocompromised individuals.