What are the key diagnostic tests for identifying protozoan infections in patients presenting with gastrointestinal symptoms?

Key diagnostic tests for identifying protozoan infections in patients with gastrointestinal symptoms include microscopic examination of stool samples, antigen detection assays, and molecular methods such as PCR. Microscopic examination remains a cornerstone, involving direct wet mounts and concentration techniques to detect cysts, trophozoites, or oocysts of protozoa like Giardia lamblia, Entamoeba histolytica, and Cryptosporidium species NICE CG84 Foreyt 1989. Antigen detection tests, particularly enzyme immunoassays (EIA), provide improved sensitivity and specificity for Entamoeba species and Giardia, allowing differentiation between pathogenic and non-pathogenic strains Fotedar et al. 2007. Molecular diagnostics, including PCR, offer high sensitivity and specificity and can identify species and genotypes, which is valuable for epidemiological studies and treatment decisions Fotedar et al. 2007. While UK guidelines emphasize stool microscopy and antigen detection as primary diagnostic tools NICE CG84, recent literature supports the increasing role of molecular methods for accurate and rapid diagnosis Fotedar et al. 2007.