Albumin, Serum

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Subject: Albumin, Serum

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Definition

  • Albumin is the most important protein and constitutes 55–65% of total plasma protein. Approximately 300–500 g of albumin is distributed in the body fluids, and the average adult liver synthesizes approximately 15 g/day. Albumin's half-life is approximately 20 days, with 4% of the total albumin pool being degraded daily. The serum albumin concentration reflects the rate of synthesis, the degradation, and the volume of distribution. Albumin synthesis is regulated by a variety of influences, including nutritional status, serum oncotic pressure, cytokines, and hormones.

  • Normal range:

    • 0–4 months: 2.0–4.5 g/dL

    • 4 months−16 years: 3.2–5.2 g/dL

    • >16 years: 3.5–4.8 g/dL

Use

  • Assess nutritional status

  • Evaluate chronic illness

  • Evaluate liver disease

Interpretation

Increased In

  • Dehydration

  • High-protein diet

Decreased In

  • Decreased synthesis by the liver:

    • Acute and chronic liver disease (e.g., alcoholism, cirrhosis, hepatitis)

    • Malabsorption and malnutrition

    • Fasting, protein–calorie malnutrition

    • Amyloidosis

    • Chronic illness

    • DM

    • Decreased growth hormone levels

    • Hypothyroidism

    • Hypoadrenalism

    • Genetic analbuminemia

  • Acute-phase reaction, inflammation, and chronic diseases:

    • Bacterial infections

    • Monoclonal gammopathies and other neoplasms

    • Parasitic infestations

    • Peptic ulcer

    • Prolonged immobilization

    • Rheumatic diseases

    • Severe skin disease

  • Increased loss over body surface:

    • Burns

    • Enteropathies related to sensitivity to ingested substances (e.g., gluten sensitivity, Crohn disease, ulcerative colitis)

    • Fistula (gastrointestinal or lymphatic)

    • Hemorrhage

    • Kidney disease

    • Rapid hydration or overhydration

    • Repeated thoracentesis or paracentesis

    • Trauma and crush injuries

  • Increased catabolism:

    • Fever

    • Cushing disease

    • Preeclampsia

    • Thyroid dysfunction

  • Plasma volume expansion:

    • CHF

    • Oral contraceptives

    • Pregnancy

Limitations

  • In clinical practice, one of the two dye-binding assays—bromocresol green (BCG) and bromocresol purple (BCP)—is used for measuring albumin levels, and systematic differences between these methods have long been recognized.

  • BCG methods are subject to nonspecific interference from binding to nonalbumin proteins, whereas BCP is more specific. BCP has been shown to underestimate serum albumin in pediatric patients on hemodialysis and patients in chronic renal failure. Chronic dialysis units often have little influence over the method.

  • Antialbumin antibodies are commonly found with hepatic dysfunction and are typically of IgA type.

  • Ischemia-modified albumin, in which the metal-binding capacity of albumin has decreased due to exposure to ischemic events, is a biologic marker of myocardial ischemia.

 
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