What are the key diagnostic tests for confirming a Cryptosporidium infection in a patient presenting with acute gastroenteritis?

The key diagnostic tests for confirming a Cryptosporidium infection in a patient presenting with acute gastroenteritis include stool microscopy with acid-fast staining, antigen detection assays, and molecular methods such as PCR. Stool microscopy using modified acid-fast staining is a traditional method to identify Cryptosporidium oocysts in stool samples, providing direct visual confirmation of the parasite ¹. Antigen detection tests, including enzyme immunoassays (EIA), offer higher sensitivity and specificity compared to microscopy and are widely used in clinical practice for rapid diagnosis ¹. Molecular techniques like polymerase chain reaction (PCR) provide the most sensitive and specific detection, allowing for confirmation even in low parasite burdens and enabling species differentiation, which can be important for epidemiological purposes (Gerace et al., 2019).

In clinical practice, initial testing often starts with antigen detection assays due to their rapid turnaround and ease of use, with microscopy or PCR reserved for confirmatory testing or in cases where initial tests are inconclusive. This integrated approach aligns with UK guidelines on managing infectious gastroenteritis, which recommend targeted testing for Cryptosporidium in patients with persistent diarrhoea or relevant exposure history ¹.