A critical assessment of two real-time PCR assays targeting the (SSU) rRNA and gdh genes for the molecular identification of Giardia intestinalis in a clinical laboratory

Introduction Giardiasis is an intestinal diarrhoeal illness caused by the flagellate protozoan parasite Giardia intestinalis. Molecular techniques for the identification of G. intestinalis have generally been shown to offer a better detection rate of the parasite than the traditional faecal concentration and microscopy techniques. Aim The aim of this study was to critically assess the performance of a commercial and a published real-time PCR assay for their potential use as frontline tests for the diagnosis of giardiasis. Methods A composite reference standard of enzyme immunoassay and rapid membrane test was used in a diagnostic accuracy study to assess the performance of Primerdesign's, and Verweij et al G. intestinalis real-time PCR assays, comparing them with the traditional ova, cysts and parasite microscopy test (OCP-M). Results The Verweij real-time PCR used primers for the (SSU) rRNA gene, and produced a diagnostic sensitivity of 93.4% (95% CI 88.30% to 98.50%) and an efficiency of 100%. Primerdesign's real-time PCR used primers for the glutamate dehydrogenase gene and produced a diagnostic sensitivity of 61.5% (95% CI 51.50% to 71.50%) and an efficiency of 203%. The OCP-M sensitivity was 83.5% (95% CI 75.87% to 91.13%). Conclusions The Verweij real-time PCR was robust and the most sensitive assay suited for use as a first-line diagnostic test for giardiasis.