An ova and parasites (O&P) test is a lab test that checks a stool sample for parasites or their eggs (ova) and cysts, which are protective shells that some parasites form. This test helps diagnose parasitic infections, such as those from Giardia, Entamoeba histolytica, or hookworms, which can cause symptoms like persistent diarrhea or other intestinal problems. To collect the sample, you provide a stool specimen in a special container to prevent contamination with urine or toilet water