Evaluation of a real-time polymerase chain reaction assay for the laboratory diagnosis of giardiasis☆
Received 3 April 2009; accepted 6 October 2009. published online 11 November 2009.
Abstract
A real-time polymerase chain reaction (PCR) assay was evaluated in comparison with the combination of conventional methods (microscopic examination and antigen detection assay) during the period 2006 to 2008 on 771 fecal samples belonging to 386 patients to assess its usefulness for an accurate laboratory diagnosis of giardiasis. The real-time PCR assay detected Giardia intestinalis DNA in 195 samples (106 patients), including 26 samples (21 patients) negative by the conventional assays. Among the 21 patients, in 8 cases, giardiasis was previously diagnosed also by conventional methods in additional samples of the same patients, whereas in 13, it would have been undiagnosed if real-time PCR assay was not used. The real-time PCR assay demonstrated a detection limit of 2 cysts per reaction and 100% specificity and sensitivity compared to conventional methods. A genotype analysis targeting the β-giardin gene allowed to identify 53 samples (23 patients) containing genotype A and 59 samples (45 patients) containing genotype B.
☆ AC and CG conceived and designed the experiments. AC, CG, SM, SP, and GP performed the experiments. SM, FG, and NM performed the sequencing. CG, SM, and GP did the sequence analysis. AC, CG, and SM wrote the paper. AC, and SR performed the conventional parasitologic diagnostic methods. GD and CC conducted the scientific supervision of the manuscript.
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