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Diagnostic Methods
Diagnostic methodsPros and cons
Parasitological diagnosis 
Giardia cysts and trophozoites can be detected in faecal samples. Since Giardia is not regularly found in the stools, multiple samples have to be analysed.
As a supplement, duodenal samples can be analysed (in aspirates or using the “Entero-Test”).
  • Sensitivity of routine stool examination is limited
  • Multiple stool samples are needed for adequate sensitivity
Molecular diagnosis 
Real-time PCR or nested PCR amplifying the small subunit ribosomal RNA gene to detect and quantify G. lamblia trophozoites. The detection limit for the rt-PCR is 50 trophozoites per gram stool.
  • Microscopy needs more samples to reach similar sensitivity
  • High sensitivity and specificity
  • Amplification product can be used for genotyping
  • Under development: multiplex rt-PCR assays to detect several pathogens in one test
Antigen detection 
Several commercially available test kits detect with a high sensitivity Giardia copro-antigens in faecal samples by immunochromatographic, immunoenzyme or direct fluorescent antibody assays.
  • One or two stool samples are in most cases sufficient
  • Excellent specificity
  • Various demands on sample preparation are test dependent (either fresh, frozen or fixed stools)
  • Detection of only one pathogen (however there is a combination test with Cryptosporidium or the Triage Micro Parasite Panel assay which also includes E. histolytica/E. dispar)
Antibody detection 
Not of diagnostic relevance since it cannot distinguish past from acute infection.