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Direct Bilirubin, Protein-Bound (Delta Bilirubin) — Mass Concentration

Published: August 9, 2026Updated: August 16, 2026

Measures protein-bound direct bilirubin in blood. This fraction, also called delta bilirubin, is usually interpreted along with total and direct bilirubin results.

Quick summary

["This test helps evaluate bilirubin processing by the liver and may be especially relevant when jaundice is present."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
56906-1
Short code
Bilirub Direct Prt-mCnc
Synonyms
Bilirub Direct Prt-mCnc
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

This test measures the amount of direct bilirubin associated with protein in a blood sample. Direct bilirubin is processed by the liver and can be released into bile; bilirubin that remains bound to protein may be reported as delta bilirubin.

Why might I need this test?

It may be ordered to help evaluate jaundice, liver function, or impaired bile flow. It is also relevant in newborns and infants, when an elevated direct bilirubin fraction may indicate a problem with bile processing or drainage.

How is the test performed?

A blood sample is collected and analyzed in the laboratory using methods that distinguish direct bilirubin from other bilirubin forms. The protein-bound result is generally considered together with total and other direct bilirubin measurements.

How do I prepare for the test?

No special preparation is usually required for this test alone. Follow your healthcare professional's instructions, particularly if the test is part of a broader panel that may require fasting.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Protein-bound direct bilirubin

Frequently asked questions

Is protein-bound direct bilirubin the same as direct bilirubin?
It is a component or related form that may be included in some direct-bilirubin measurements. It is also commonly called delta bilirubin, so check the laboratory report for the exact label used.
Does an abnormal result mean I have liver disease?
Not necessarily. Abnormal bilirubin results can have several causes and are interpreted together with other liver tests, imaging, symptoms, and medical history.
Why is this result important in a newborn?
Newborns can have physiologic jaundice, but elevated direct bilirubin may indicate impaired bile processing or drainage. Prompt review by the newborn's healthcare professional is important.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy