What are the two methods listed for fecal testing?

• A. Floatation and centrifugation
• B. Sedimentation and direct smear
• C. Culture and staining
• D. Filtration and decantation

Answer: (A)

Fecal parasite testing hinges on bringing parasite eggs, cysts, or oocysts out of the stool so they can be seen under a microscope. The two main approaches used are flotation and centrifugation.

Flotation uses a solution with higher specific gravity than the parasite stages. When the stool is mixed with this buoyant liquid, the eggs and oocysts ride to the surface and can be collected on a coverslip for examination. This method is especially good for many common nematode eggs and protozoan cysts because they float readily in the right solution.

Centrifugation concentrates parasite elements by spinning the sample. The centrifugal force helps pull sparse eggs or cysts into a concentrated area, increasing the likelihood of detection. Often this is used as centrifugal flotation, where spinning with a buoyant solution improves recovery compared with gravity-based flotation alone, or as a separate sedimentation/concentration step in other protocols.

These two methods cover the practical approaches used to detect parasites in fecal samples: using buoyancy to bring elements to the surface, and using centrifugal force to concentrate them for easier visualization.