Test Catalog

Test Id : TPBF

Protein, Total, Body Fluid

Useful For
Suggests clinical disorders or settings where the test may be helpful

Identification of exudative pleural effusions


Differentiating hepatic from other causes of ascites that have elevated serum ascites albumin gradient (SAAG) using peritoneal fluid

Method Name
A short description of the method used to perform the test


NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Protein, Total, BF

Lists additional common names for a test, as an aid in searching

Lights Criteria

Light's criteria

Specimen Type
Describes the specimen type validated for testing

Body Fluid

Ordering Guidance

For protein measurement in spinal fluid specimens, order TPSF / Protein, Total, Spinal Fluid. Testing will be changed to TPSF if this test is ordered on that specimen type.

Necessary Information

1. Date and time of collection are required.

2. Specimen source is required.


Question ID Description Answers
FLD23 Fluid Type, Protein, Total

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Specimen Type: Body fluid

Preferred Source:

-Peritoneal fluid (peritoneal, abdominal, ascites, paracentesis)

-Pleural fluid (pleural, chest, thoracentesis)

-Drain fluid (drainage, JP drain)


Acceptable Source: Write in source name with source location (if appropriate)

Collection Container/Tube: Sterile container

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Centrifuge to remove any cellular material and transfer into a plastic vial.

2. Indicate the specimen source and source location on label.


If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject
Anticoagulant or additive Breast milk Nasal secretions Gastric secretions Bronchoalveolar lavage (BAL) or bronchial washings Colostomy/ostomy Feces Cerebrospinal fluid Saliva Sputum Urine Vitreous fluid Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Body Fluid Refrigerated (preferred) 7 days
Frozen 30 days
Ambient 24 hours

Useful For
Suggests clinical disorders or settings where the test may be helpful

Identification of exudative pleural effusions


Differentiating hepatic from other causes of ascites that have elevated serum ascites albumin gradient (SAAG) using peritoneal fluid

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Pleural fluid:

Pleural fluid is normally present within the pleural cavity surrounding the lungs, serving as a lubricant between the lungs and inner chest wall. Pleural effusion develops when the pleural cavity experiences an overproduction of fluid due to increased capillary hydrostatic and osmotic pressure that exceeds the ability of the lymphatic or venous system to return the fluid to circulation. Laboratory-based criteria are often used to classify pleural effusions as either exudative or transudative. Exudative effusions form due to infection or inflammation of the capillary membranes allowing excess fluid into the pleural cavity. Patients with these conditions benefit from further investigation and treatment of the local cause of inflammation. Transudative effusions form due to systemic conditions such as volume overload, end stage renal disease, and heart failure that can lead to excess fluid accumulation in the pleural cavity. Patients with transudative effusions benefit from treatment of the underlying condition.(1)


Dr. Richard Light derived criteria in the 1970s that are still used today for patients with pleural effusions.(2)


The criteria include the measurement of total protein and lactate dehydrogenase (LDH) in pleural fluid and serum. Exudates are defined as meeting 1 of the following criteria:

1. Pleural fluid to serum protein ratio above 0.5

2. Pleural fluid LDH above two-thirds the upper limit of normal serum LDH

3. Pleural fluid to serum LDH ratio above 0.6


Dr. Light's criteria were designed to be sensitive for detecting exudates at the expense of specificity.(3) Heart failure and recent diuretic use contribute to most misclassifications by Dr. Light's criteria (transudates falsely categorized as exudates). Serum-to-fluid protein gradient (serum protein minus fluid protein) may be calculated in these cases and when more than 3.1 g/dL suggests the patient has a transudative effusion.


Peritoneal fluid:

The pathologic accumulation of fluid within the peritoneal cavity is commonly referred to as ascites. The most common cause of ascites is liver cirrhosis. Differentiating cardiac from cirrhotic ascites is a common clinical conundrum as they are common conditions presenting with elevated serum ascites albumin gradient (SAAG).(4) Heart failure leads to the development of high gradient ascites due to hepatic sinusoidal hypertension. Since the sinusoids are normal and have not been damaged from collagen deposition associated with cirrhosis, protein tends to "leak" more readily into ascites and is associated with higher total protein concentrations.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Provides information to assist in interpretation of the test results

A pleural fluid total protein to serum total protein ratio of above 0.5 is most consistent with exudative effusion.(2,5)


A peritoneal fluid total protein of above 2.5 g/dL in patients with a high serum ascites albumin gradient (SAAG) can be caused by heart failure. A peritoneal fluid total protein of over 1.0 g/dL helps to differentiate secondary from spontaneous bacterial peritonitis in conjunction with other laboratory, imaging and clinical findings.(6,7,8)


The usefulness of measuring total protein in pericardial fluid is not well documented. Results may be interpreted in conjunction with serum or plasma total protein concentrations.


The usefulness of measuring total protein in synovial fluid is limited as it has poor sensitivity and specificity for differentiating inflammatory vs non-inflammatory causes and should be interpreted in conjunction with other clinical findings.(9)


All other fluids: Total protein may be used to differentiate transudative from exudative effusions. The decision limits are not well defined in fluids other than pleural fluid and should be interpreted in conjunction with other clinical findings.(10)

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

In very rare cases, gammopathy, in particular type IgM (Waldenstrom macroglobulinemia), may cause unreliable results.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Block DR, Florkowski CM: Body fluids. In: Rafai N, Horvath AR, Wittwer CT. eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier;2018:chap43

2. Light RW: The Light criteria: the beginning and why they are useful 40 years later. Clin Chest Med. 2013 Mar;34(1):21-26

3. Porcel JM: Identifying transudates misclassified by Light's criteria. Curr Opin Pulm Med. 2013;19:362-367

4. Block DR, Genzen JR: Diagnostic body fluid testing. In: Clarke W, ed. Contemporary Practice in Clinical Chemistry. 3rd ed. AACC Press; 2016:773-775

5. Sahn SA: Getting the most from pleural fluid analysis. Respirology. 2012;17:270-277

6. Runyon BA: AASLD Practice Guideline. Management of adult patients with ascites due to cirrhosis: update 2012. Hepatology. 2013;57:1-26  

7. McGibbon A, Chen GI, Peltekian KM, van Zanten SV: An evidence-based manual for abdominal paracentesis. Dig Dis Sci. 2007;52:3307-3315

8. Runyon BA, Montano AA, Akriviadis EA, Antillon MR, Irving MA, McHutchison JG: The serum-ascites gradient is superior to the exudate-transudate concept in the differential diagnosis of ascites. Ann Intern Med. 1992;117:215-220

9. Shmerling RH, Delbanco TL, Tosteson AN, Trentham DE: Synovial fluid tests: what should be ordered? JAMA. 1990;264:1009-1014

10. Brunzel NA: Pleural, pericardial, and peritoneal fluid analysis. In: Fundamentals of Urine and Body Fluid Analysis. WB Saunders Company; 1994:406

Method Description
Describes how the test is performed and provides a method-specific reference

Divalent copper reacts in alkaline solution with protein peptide bonds to form the characteristic purple-colored biuret complex. Sodium potassium tartrate prevents the precipitation of copper hydroxide and potassium iodide prevents auto-reduction of copper. The color intensity is directly proportional to the protein concentration which can be determined photometrically.(Package insert: Roche Protein reagent. Roche Diagnostics; 01/2020)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Sunday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

Same day/1 to 2 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

1 week

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
TPBF Protein, Total, BF 2881-1
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
TPBF1 Protein, Total, BF 2881-1
FLD23 Fluid Type, Protein, Total 14725-6

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports