Real-time PCR for the detection of Giardia lamblia

Microscopy is considered to be the gold standard for diagnosis of Giardia lamblia infection. However, this method is time-consuming and not very sensitive. We developed a real-time PCR assay based on the small subunit ribosomal RNA gene of G. lamblia for the specific detection of G. lamblia DNA in stool samples and thereafter compared the results with microscopy and antigen detection. The G. lamblia real-time PCR was positive in 102 of 104 fecal samples known to contain G. lamblia cysts and was positive in 10 fecal samples in which G. lamblia antigen was detected but in which no cysts were found with microscopic examination of concentrated fecal samples. The real-time PCR is as specific and sensitive as antigen detection and is more sensitive than microscopy. Moreover, in two patients we were able to detect G. lamblia earlier in the course of infection than with any of the other methods.