From the Guidelines
The proper way to check for ova and parasites involves collecting at least three fresh stool specimens collected on different days, as parasites are shed intermittently, with a sensitivity of approximately 60–90% for detection of these organisms 1. To accurately diagnose ova and parasites, patients should provide separate stool specimens collected over multiple days. Each sample should be fresh, collected within 30 minutes of defecation, or preserved immediately in appropriate fixatives.
- Samples should not be contaminated with urine, water, or toilet chemicals.
- Patients should use clean, dry containers and avoid collecting samples during menstruation or while using certain medications like antibiotics, antidiarrheals, antacids, or barium, as these can interfere with detection.
- The laboratory examination typically includes direct microscopy, concentration techniques, and special stains to identify eggs, cysts, larvae, or adult parasites.
- Multiple collection days are necessary because parasites often have cyclical shedding patterns, and a single negative sample does not rule out infection. However, according to the AGA clinical practice guidelines, in patients presenting with chronic diarrhea with no travel history to or recent immigration from high-risk areas, testing for ova and parasites (other than Giardia) is not recommended due to low-quality evidence 1. In cases where Giardia infection is suspected, a stool ELISA with 92% sensitivity and 98% specificity can be used, replacing the need for intestinal biopsies and wet preparations 1.
From the Research
Diagnosing Ova and Parasites
To diagnose ova and parasites, several methods are recommended, depending on the type of infection:
- Stool microscopy with direct fluorescent antibody testing is recommended for diagnosing Giardia infection 2
- Microscopy with immunofluorescence is sensitive and specific for diagnosing Cryptosporidium infection 2
- Microscopy or polymerase chain reaction assays are recommended to diagnose Cyclospora infections 2
- Serum antibody testing is used to diagnose Trichinella infection 2
- Pinworm infections can be diagnosed visually or by a tape test or paddle test 2
Laboratory Tests
Laboratory tests play a crucial role in diagnosing ova and parasites:
- Stool samples are often used to diagnose intestinal parasites 2
- Direct fluorescent antibody testing and immunofluorescence can be used to detect specific parasites 2
- Polymerase chain reaction assays can be used to diagnose Cyclospora infections 2
Note on Relevance of Studies
The study on long-term culture of guinea pig tongue cells 3 is not directly relevant to the diagnosis of ova and parasites. Therefore, it is not considered in the recommended methods for diagnosing ova and parasites. The information provided is based on the study on common intestinal parasites 2.