What are the recommended diagnostic tests for confirming a Giardia lamblia infection in adults?

The recommended diagnostic tests for confirming Giardia lamblia infection in adults primarily involve stool analysis. The first-line approach is to perform microscopic examination of stool samples for Giardia cysts or trophozoites, ideally using multiple stool specimens collected on different days to increase sensitivity.

Additionally, antigen detection assays such as enzyme immunoassays (EIA) or immunofluorescence assays (IFA) targeting Giardia-specific antigens in stool are recommended due to their higher sensitivity and specificity compared to microscopy alone.

Molecular methods like polymerase chain reaction (PCR) can also be used for detection and confirmation, offering greater sensitivity, but are generally reserved for complex cases or reference laboratories.

In summary, the diagnostic pathway integrates stool microscopy with antigen detection tests as standard practice, with PCR as an adjunct when needed.

This approach aligns with UK clinical practice guidelines emphasizing stool examination and antigen testing ¹, while the literature supports the enhanced sensitivity of antigen detection and molecular methods (Cook, 1995).