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The Rivalta test is an inexpensive biochemistry test that differentiates exudate from transudate. Rivalta, an Italian researcher in 1900, initially devised the test. It is also used in diagnosing Feline Infectious Peritonitis in cats.
The test should not be confused with Pandy’s test which checks for elevated levels of proteins in cerebral spinal fluid.
Some infections cause fluids to accumulate in certain parts of the body, such as the ascites (abdomen) or pleural effusion (lungs), or pericardial (heart).
The test helps narrow down the infection by determining the quantity of proteins in the fluid. Transudates have a lower protein concentration than exudates.
In cats, the test helps to differentiate between effusions caused by Feline Infectious Peritonitis (FIP) and other diseases. FIP is a viral disease that affects cats.
Also read: All Biochemistry tests list (A -Z).
Rivalta test in humans
In humans, some diseases can cause fluid accumulation in various organs. The test helps determine the concentration of proteins in the accumulated fluid, which helps in the differential diagnosis.
Fluid accumulations caused by tuberculosis and cancer have higher protein content (exudate), while those caused by liver or heart failure have a lower protein content (transudate).
Rivalta is an inexpensive test that helps differentiate transudates from exudates.
Note: High concentrations of inflammatory mediators and fibrinogen can cause positive results.
Rivalta test in cats
The Rivalta test helps diagnose Feline Infectious Peritonitis (FIP), a frequent and fatal cat disease.
FIP is an immune-mediated infection caused by feline coronavirus (FCoV). The disease is difficult to diagnose and almost impossible to diagnose, making it a primary concern among veterinarians.
FCoV is transmissible through the fecal-oral route but does not infect other species. The exact way that FIP develops is not clear. One theory (internal mutation theory) suggests that a mutation favors the virus to replicate in macrophages. The other theory suggests that FCoV causes FIP when the viral load is high and the cat’s immunity is compromised.
Infected cats present with lesions on the central nervous system, parenchymatous organs, eyes, and vasculitis manifesting as ascites and effusions (pericardial, thoracic, and scrotal).
Positive Rivalta test can occur in cats with lymphoma or bacterial peritonitis. The effusion can be differentiated through bacterial culture, macroscopic, and cytological examinations.
Read more: FIP in Cats: Symptoms, tests, statistics, and treatment.
Rivalta test principle
The Rivalta test principle relies on the formation of a precipitate when an effusion is added to acetic acid. This helps differentiate whether a fluid is an exudate or a transudate. Exudates have a higher concentration of proteins than transudates.
Lower concentrations of proteins will dissolve in the acetic acid solution used in the Rivalta test, while higher concentrations do not. This allows for the differentiation between transudates and exudates based on the protein concentration in the fluid sample being tested.
Testing guidelines
Researchers are yet to standardize the Rivalta test, but they are conducting multiple research projects to determine the specificity and sensitivity of this test. It, however, is essential to note that the test has a high success rate of diagnosing FIP in felines.
Test requirements include protective gloves, distilled water, a transparent reagent bottle, acetic acid, and a pipette.
NOTE: The test checks for elevated protein levels in effusions; a negative result does not mean an absence of proteins.
Rivalta test procedure
- Pour out 8mL of distilled water into a 10ml reagent bottle.
- Add a drop of acetic acid (98% vinegar) and mix thoroughly.
- Carefully layer one drop of effusion on the surface of the solution. DO NOT MIX.
- Hold the preparation against a dark background and note the appearance of the drop.
The test result is negative if the drop dissolves into the reagent and remains clear. If the drop retains its shape, slowly floats down to the bottom, or stays attached to the surface, the test result is positive.
Conclusion
The Rivalta test is a valuable tool for differentiating between transudates and exudates and diagnosing FIP in cats. It is simple, inexpensive, and can be easily performed in private practice or resource-limited settings. By understanding the principle, procedure, and interpretation of the Rivalta test, clinicians can use it to help establish a diagnosis for certain diseases.
