Certain diseases can cause excessive accumulations of fluid in areas of the body such as the abdomen (ascites) or the pleural space around the lungs (pleural effusion) or the pericardial space around the heart. An estimate of the concentration of protein in such fluids can narrow the differential diagnosis and assist the clinician in establishing a diagnosis. For example, fluid accumulations due to congestive heart failure and liver failure (cirrhosis) are typically lower in protein content and are called transudates whereas fluid accumulations due to cancer and tuberculosis are typically higher in protein content and are called exudates. The Rivalta Test is a simple, inexpensive method that can be used in resource-limited settings to differentiate a

transudate Transudate is extravascular fluid with low protein content and a low specific gravity (< 1.012). It has low nucleated cell counts (less than 500 to 1000 per microliter) and the primary cell types are mononuclear leukocyte, mononuclear cells: macrop ...

from an

exudate An exudate is a fluid released by an organism through pores or a wound, a process known as exuding or exudation. ''Exudate'' is derived from ''exude'' 'to ooze' from Latin language, Latin 'to (ooze out) sweat' (' 'out' and ' 'to sweat'). Medi ...

. It is a simple, inexpensive method that does not require special laboratory equipment and can be easily performed in private practice. The test was originally developed by the Italian researcher Rivalta around 1900 and was used to differentiate transudates and exudates in human patients. It is also useful in cats to differentiate between effusions due to feline infectious peritonitis (FIP) and effusions caused by other diseases.Hartmann et al., 2003 Not only the high protein content, but high concentrations of fibrinogen and inflammatory mediators lead to a positive reaction.

Method

A test tube is filled with distilled

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

and

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main compone ...

is added. To this mixture one drop of the effusion to be tested is added. If the drop dissipates, the test is negative, indicating a transudate. If the drop precipitates, the test is positive, indicating an exudate. Using a pH 4.0 acetic acid solution, 8 types of proteins were identified in Rivalta reaction-positive turbid precipitates:

C-reactive protein C-reactive protein (CRP) is an annular (ring-shaped) pentameric protein found in blood plasma, whose circulating concentrations rise in response to inflammation. It is an acute-phase protein of hepatic origin that increases following interleukin ...

(CRP),

Alpha 1-antitrypsin Alpha-1 antitrypsin or α1-antitrypsin (A1AT, α1AT, A1A, or AAT) is a protein belonging to the serpin superfamily. It is encoded in humans by the ''SERPINA1'' gene. A protease inhibitor, it is also known as alpha1–proteinase inhibitor (A1P ...

(alpha1-AT),

Orosomucoid Introduction Orosomucoid (ORM) or alpha-1-acid glycoprotein (''α1AGp'', ''AGP'' or ''AAG'') is an acute phase protein found in blood plasma, plasma. Orosomucoid was discovered over 70 years ago and belongs to the lipocalin protein family. The ...

((Alpha-1-acid glycoprotein or AGP)),

haptoglobin Haptoglobin (abbreviated as Hp) is the protein that in humans is encoded by the ''HP'' gene. In blood plasma, haptoglobin binds with high affinity to ''free'' hemoglobin released from erythrocytes, and thereby inhibits its deleterious oxidativ ...

(Hp),

transferrin Transferrins are glycoproteins found in vertebrates which bind and consequently mediate the transport of iron (Fe) through blood plasma. They are produced in the liver and contain binding sites for two Iron(III), Fe3+ ions. Human transferrin is ...

(Tf),

ceruloplasmin Ceruloplasmin (or caeruloplasmin) is a ferroxidase enzyme that in humans is encoded by the ''CP'' gene. Ceruloplasmin is the major copper-carrying protein in the blood, and in addition plays a role in iron metabolism. It was first described in ...

(Cp),

fibrinogen Fibrinogen (coagulation factor I) is a glycoprotein protein complex, complex, produced in the liver, that circulates in the blood of all vertebrates. During tissue and vascular injury, it is converted Enzyme, enzymatically by thrombin to fibrin ...

(Fg), and hemopexin (Hpx). Since those are

Acute-phase proteins Acute-phase proteins (APPs) are a class of proteins whose concentrations in blood plasma either increase (positive acute-phase proteins) or decrease (negative acute-phase proteins) in response to inflammation. This response is called the ''acute-p ...

, a positive Rivalta's test may be suggestive of

inflammation Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...

Procedure

To perform this test, a transparent reagent tube (volume 10 ml) is filled with approximately 7–8 ml distilled water, to which 1 drop of acetic acid (8%, plain white vinegar) is added and mixed thoroughly. On the surface of this solution, 1 drop of the effusion fluid is carefully layered. If the drop disappears and the solution remains clear, the Rivalta's test is defined as negative. If the drop retains its shape, stays attached to the surface or slowly floats down to the bottom of the tube (drop- or jelly-fish-like), the Rivalta's test is defined as positive. The Rivalta's test had a high positive predictive value (86%) and a very high negative predictive value for FIP (96%) in a study in which cats that presented with effusion were investigated (prevalence of FIP 51%). Positive Rivalta's test results can occur in cats with bacterial peritonitis or lymphoma.

References

{{reflist * http://abcd-vets.org/guidelines/feline_infectious_peritonitis/chapter-5.asp Medical tests