Which diagnostic method is typically used to confirm the presence of Giardia lamblia?

The stool antigen test is the preferred diagnostic method for confirming the presence of Giardia lamblia, a protozoan parasite that causes gastrointestinal infections known as giardiasis. This test detects specific antigens that are released by the parasite in the stool. It is favored because it offers high sensitivity and specificity, allowing for reliable identification of active Giardia infections.

In contrast, serological testing primarily involves identifying antibodies in the blood, which may not be as effective for diagnosing a current infection since antibodies can take time to develop after exposure. Blood cultures are used to identify bacterial pathogens rather than protozoan parasites like Giardia, making them unsuitable for this diagnosis. Skin scraping is a technique used for identifying certain skin infections, typically fungal or ectoparasitic in nature, but has no relevance to diagnosing giardiasis.

Thus, the stool antigen test directly assesses the presence of the organism in the most relevant specimen, thereby establishing it as the most effective diagnostic method for Giardia lamblia.