equis - Articles
Blood: biochemistry – direct bilirubin test
Synonym(s): Conjugated bilirubin
Overview
- Serum bilirubin is a mixture of direct and indirect bilirubin.
- Peripheral breakdown of red cells and myoglobin → uncongugated bilirubin → (liver) conjugated with glucuronic acid → excreted in bile as conjugated (direct) bilirubin.
- Presence and degree of icterus in equine serum/plasma is difficult or impossible to evaluate maroscopically due to variable carotenoid pigments that are present, often influenced by diet.
Uses
In combination
- With total bilirubin Blood: biochemistry - total bilirubin :
- Assessment of liver damage.
- Diagnosis of biliary obstruction.
- With liver enzymes (ALP Blood: biochemistry - alkaline phosphatase (SAP, ALP) , GLDH, SDH (IDH), GGT Blood: biochemistry - gamma glutamyl transferase (gGT) , AST Blood: biochemistry - aspartate amino transferase (AST) or bile acids Blood: biochemistry - bile acids for assessment of liver damage.
Other points
- Biliprotein (deltabilirubin) is a fraction of conjugated bilirubin irreversibly bound to albumin.
- Variable amounts are formed and it comprises 0-90% of total bilirubin in jaundiced animal.
- Degraded over 14 days (along with albumin) therefore if it is the predominant component of the hyperbilirubinemia jaundice may be protracted after disease has resolved.
Sampling
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Tests
Methodologies
- Van den Bergh method.
Availability
- Routine test, widely available.
Validity
Sensitivity
- Van den Bergh test relatively insensitive.
Technique intrinsic limitations
- Most useful when interpreted in conjunction with other laboratory and clinical findings.
Result Data
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Engleking L R & Paradis M R (1987) Evaluation of hepatobiliary disorders in the horse. Vet Clin North Am Equine Pract 3 (3), 563-583.
- Ogilvie G K, Engleking L R & Anwer M S (1985) Effects of plamsa sample storage of on blood ammonia, bilirubin and urea nitrogen concentrations - cats and horses. Am J Vet Res 46 (12), 2619-2622.
Other sources of information
- Barton M H & Morris D D (1998) Diseases of the Liver. In: Equine Internal Medicine. Eds: S M Reed & W M Bayly. W B Saunders Co, USA.
- Kaneko J J, Harvey J W & Bruss M L (1997) Eds. Clinical Biochemistry of Domestic Animals. 5th edn. Academic Press, USA.
Organisation(s)
- Veterinary commercial laboratories, State diagnostic laboratories or Veterinary College laboratories.