Hepatic Proteins

Hepatic proteins are a group of proteins synthesized in the liver that may be used in the assessment of nutritional status. Hepatic proteins include albumin, prealbumin (transthyretin), retinol-binding protein (RBP), and transferrin.

Tabs Content

Clinical Overview

Diagnosis

Indications for Testing

Known disease that would cause compromised nutritional status (eg, cancer, malabsorption)
Failure to thrive in children

Laboratory Testing

Albumin – usual first-line test in evaluating nutritional status
- Elevated concentrations – dehydration
- Decreased concentrations are very common
  - Impaired synthesis
    - Primary (eg, liver disease)
    - Secondary (eg, low protein intake)
  - Increased catabolism – result of tissue damage and inflammation
  - Reduced absorption of amino acids – malabsorption or malnutrition
  - Excessive protein loss in urine, feces, or skin – glomerulonephritis, nephrotic syndrome, protein-losing enteropathy
  - Altered distribution that sequesters large amounts of albumin in extravascular compartment
    - Nephrotic syndrome
    - Congestive heart failure
- Albumin measurement in urine may aid in early detection of renal involvement in chronic diseases
Prealbumin – may be a better early screening test due to short half-life
- Used as marker of nutritional status in
  - Premature infants
  - Cancer patients
  - Surgical patients
- Negative acute phase reactant – concentrations fall in the following diseases due to decreased synthesis
  - Inflammation
  - Malignancy
  - Cirrhosis of the liver
  - Protein-wasting diseases of the gut or kidney
- Recommended test for protein measurement in evaluation of nutrition in hospitalized patients
Retinol-binding protein (RBP), transferrin, and fecal alpha-1-antitrypsin – less widely used as screening tests
- Decreased concentrations of RBP – cystic fibrosis, liver disease
- Elevated concentrations of transferrin
  - Malnutrition
  - Acute inflammation
  - Infection
  - Renal disorders
  - Red blood cell disorders (eg, iron deficiency)
  - High concentrations can occur in pregnancy and during estrogen administration
- Decreased concentrations of transferrin
  - Transferrin is a negative acute phase reactant
  - Low concentrations occur in
    - Inflammation
    - Malignancy
    - Chronic liver disease
    - Protein loss
- Elevated fecal clearance of alpha-1-antitrypsin in protein-losing enteropathy
Vitamin/mineral assay testing also recommended

Background

Etiologies

Starvation
Chronic disease
- HIV
- Malignancy
- Chronic liver disease
- Chronic kidney disease
- Chronic obstructive pulmonary disease (COPD)
Anorexia
Malabsorption
Critical illness or trauma

Pathophysiology

Albumin
- Function – carrier protein for minerals, fatty acids, vitamins, and hormones
- Most abundant protein in human plasma – 55-65% of total protein content
- Most commonly monitored protein – long half-life (20 days) makes it a relatively insensitive marker
Prealbumin (transthyretin)
- Function – carrier protein for thyroid hormone
- 2-day half-life
  - Short half-life makes it a good indicator for early monitoring
  - Unaffected by hydration status
Retinol-binding protein (RBP)
- Function – responsible for binding and transporting retinol (vitamin A)
- Short half-life (11 hours) makes it an excellent indicator of early malnutrition
Transferrin
- Function – carrier protein for iron
- Presence of transferrin in serum and other body fluids aids in differential diagnosis
Alpha-1-antitrypsin (fecal)
- Function – protease inhibitor

Clinical Presentation

Constitutional – weight loss, muscle wasting, fatigue, failure to thrive (children)
Skin changes from vitamin deficiencies may occur in chronic loss
Extremes – kwashiorkor manifesting with ascites, edema

ARUP Lab Tests

Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

Albumin, Serum or Plasma by Spectrophotometry 0020030
Method: Quantitative Spectrophotometry

Recommended Use

Evaluate production of albumin by liver; assess nutritional status

Assess nephrotic syndrome and protein-losing enteropathy

Prealbumin, Serum 0050435
Method: Immunoturbidimetry

Recommended Use

Assess nutritional status in premature infants, in cancer patients, and surgical patients

Recommended protein measurement to evaluate nutritional status in hospitalized patients

Assess nephrotic syndrome and protein-losing enteropathy

Retinol Binding Protein 0050467
Method: Quantitative Nephelometry

Recommended Use

Indicate early malnutrition, acute and chronic hepatitic disease, advanced chronic renal insufficiency, and cystic fibrosis

Assess nephrotic syndrome and protein-losing enteropathy

Transferrin, Serum 0050570
Method: Quantitative Immunoturbidimetry

Recommended Use

Aid in differential diagnosis of malnutrition

Monitor iron deficiency anemia

Alpha-1-Antitrypsin Clearance, Quantitative by ELISA, Timed Stool 2011043
Method: Enzyme-Linked Immunosorbent Assay/Quantitative Immunoturbidimetry

Recommended Use

Follow-up test when protein-losing enteropathy is suspected

If serum or plasma specimen is not submitted in conjunction with timed stool collection, order alpha-1-antitrypsin (AAT) random stool test

Alpha-1-Antitrypsin, Quantitative by ELISA, Random Stool 2011041
Method: Quantitative Enzyme-Linked Immunosorbent Assay

Recommended Use

Follow-up test when protein-losing enteropathy is suspected

Alpha-1-Antitrypsin 0050001
Method: Quantitative Immunoturbidimetry

Recommended Use

Determine AAT enzyme plasma concentration for the initial evaluation of AAT deficiency

Acutely ill AAT-deficient patients may have falsely normal AAT concentrations

Calculations for the AAT fecal test require that this test also be ordered

Medical Experts

Delgado, Julio, MD, MS, Chief Medical Officer; Director of Laboratories; Chief, Division of Clinical Pathology at ARUP Laboratories; Associate Professor of Clinical Pathology, University of Utah

Genzen, Jonathan R., MD, PhD, Laboratory Section Chief, Clinical Chemistry, and Medical Director, Automated Core Laboratory, at ARUP Laboratories; Associate Professor of Clinical Pathology, University of Utah

Schlaberg, Robert, MD, MPH, Medical Director, Microbial Amplified Detection, Virology, and Fecal Chemistry; and Assistant Medical Director, Virology and Molecular Infectious Disease at ARUP Laboratories; Assistant Professor of Clinical Pathology, University of Utah

References

General References

Buxbaum JN, Reixach N. Transthyretin: the servant of many masters. Cell Mol Life Sci. 2009; 66(19): 3095-101. PubMed

Danziger J. Importance of low-grade albuminuria. Mayo Clin Proc. 2008; 83(7): 806-12. PubMed

Ellegård LH, Bosaeus IG. Biochemical indices to evaluate nutritional support for malignant disease. Clin Chim Acta. 2008; 390(1-2): 23-7. PubMed

Kmieć Z. Cooperation of liver cells in health and disease. Adv Anat Embryol Cell Biol. 2001; 161: III-XIII, 1-151. PubMed

Pencharz PB. Assessment of protein nutritional status in children. Pediatr Blood Cancer. 2008; 50(2 Suppl): 445-6; discussion 451. PubMed

Perez Valdivieso JR, Bes-Rastrollo M, Monedero P, de Irala J, Lavilla FJ. Impact of prealbumin levels on mortality in patients with acute kidney injury: an observational cohort study. J Ren Nutr. 2008; 18(3): 262-8. PubMed

Suzuki N, Kida K, Suzuki K, Harada T, Akashi YJ. Assessment of transthyretin combined with mini nutritional assessment on admission provides useful prognostic information in patients with acute decompensated heart failure. Int Heart J. 2015; 56(2): 226-33. PubMed

Last Update: July 2018

Hepatic Proteins

Diagnosis

Indications for Testing

Laboratory Testing

Background

Etiologies

Pathophysiology

Clinical Presentation

ARUP Lab Tests

Medical Experts

References

General References

ARUP Laboratories

ARUP Websites

ARUP Consult


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	Hepatic Proteins. ARUP Consult^©. Retrieved December 16, 2018, from: https://arupconsult.com/content/proteins