Which test on effusion is commonly used as supportive evidence for FIP?

• A. Rivalta test on effusion
• B. Urinalysis
• C. Serum creatinine
• D. Reticulocyte count

Answer: (A)

Rivalta testing of the effusion is a quick, inexpensive way to gauge whether an effusion is inflammatory and protein-rich, which fits with what is seen in FIP. In this test, a drop of the effusion is mixed with a drop of a water-acetic acid solution; a positive result appears as a opaque, jelly-like precipitate that remains or slowly sinks, indicating an inflammatory exudate. This supports FIP when paired with other signs, but it isn’t definitive on its own. Urinalysis, serum creatinine, and reticulocyte counts don’t assess the inflammatory nature of the effusion or provide FIP-specific support, so they aren’t used as evidence for FIP in this context.