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Lipopolysaccharide binding protein (LBP)

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CONVENTIONAL UNITS

(Acute-Phase Reactant – Early Marker of Sepsis, Endotoxemia & Gram-Negative Inflammation)

Synonyms

  • LBP
  • Lipopolysaccharide-binding protein
  • Endotoxin-binding protein
  • LPS carrier protein
  • Acute-phase LPS transport protein

Units of Measurement

  • mg/L
  • mg/dL
  • mg/100 mL
  • mg%
  • µg/mL

Key Conversions

1 mg/dL = 10 mg/L
 1 µg/mL = 1 mg/L
 mg% = mg/dL = mg/100 mL

LBP is measured in mass units (not molar units).

Description

Lipopolysaccharide Binding Protein (LBP) is a liver-derived acute-phase protein that binds to LPS (endotoxin) from the outer membrane of Gram-negative bacteria.

Functions:

  • Detects circulating endotoxin
  • Presents LPS to CD14/TLR4 receptors
  • Initiates innate immune responses
  • Regulates inflammatory cascades in sepsis

LBP levels increase dramatically during infection and inflammation, especially with Gram-negative sepsis.

Physiological Role

1. Recognition of Endotoxin (LPS)

LBP binds to LPS with high affinity → forms LBP–LPS complex.

2. Innate Immune Activation

LBP delivers LPS to:

  • CD14
  • MD-2
  • TLR4

This triggers:

  • TNF-α
  • IL-1β
  • IL-6
  • IL-8
  • Neutrophil activation

3. Acute-Phase Response

LBP increases 10–100× in sepsis.

4. Endotoxin Clearance

Transfers LPS to lipoproteins → detoxification.

Clinical Significance

HIGH LBP

(Most important)

1. Early Marker of Sepsis

LBP rises earlier than CRP, often within 6–12 hours.

Strong association with:

  • Gram-negative bacteremia
  • Endotoxemia
  • Septic shock

2. Gram-Negative Infections

LBP elevations correlate with:

  • E. coli
  • Klebsiella
  • Pseudomonas
  • Acinetobacter

3. Systemic Inflammation

LBP increases in:

  • Severe pneumonia
  • Meningitis
  • Urinary tract infections
  • COVID-19 cytokine activity
  • Burns
  • Trauma
  • Major surgery

4. Inflammatory Bowel Disease

Especially in:

  • Crohn’s disease
  • Ulcerative colitis with bacterial translocation

5. Cirrhosis & Gut Translocation

Portal hypertension → endotoxin leakage → ↑ LBP.

6. Neonatal Sepsis

LBP is a helpful early biomarker alongside IL-6 & procalcitonin.

LOW LBP

Rarely clinically important; may occur in:

  • Severe liver failure (reduced synthesis)
  • Profound immunosuppression
  • Early neonatal life

Reference Intervals

(Tietz 8E + Mayo + ARUP + sepsis biomarker studies)

Adults

  • 5 – 15 mg/L

Mild Elevation

  • 15 – 25 mg/L

Moderate Elevation

  • 25 – 40 mg/L

High Elevation

  • >40 mg/L

Strongly Suggestive of Sepsis / Endotoxemia

  • >50–60 mg/L

Critical Elevation

  • >100 mg/L

(Ranges vary by method; interpret alongside CRP, PCT, IL-6.)

Diagnostic Uses

1. Early Sepsis Detection

LBP rises earlier than:

  • CRP
  • ESR
  • Ferritin

Useful when clinical suspicion is high.

2. Gram-Negative Bacteremia

LBP specifically detects endotoxin exposure.

3. Monitoring Severity in Sepsis

LBP correlates with:

  • Organ dysfunction
  • Vasopressor requirement
  • Mortality risk

4. Neonatal Sepsis

Combines well with IL-6 and procalcitonin for early detection.

5. Inflammatory Bowel Disease Activity

Reflects bacterial translocation.

6. Cirrhosis with Bacterial Translocation

Elevated due to increased gut permeability.

7. COVID-19 Hyperinflammation

LBP elevated due to gut–lung axis and systemic endotoxin leakage.

Analytical Notes

  • Serum or EDTA plasma acceptable
  • No fasting required
  • Stable at room temperature for several hours
  • Assayed by immunoassay (ELISA/turbidimetry)
  • Should be interpreted with CRP, procalcitonin, IL-6, and clinical context

Clinical Pearls

  • LBP rises before CRP, making it a valuable early sepsis marker.
  • In Gram-negative sepsis, LBP can increase 10–100×.
  • High LBP + high IL-6 = strong evidence of endotoxemia.
  • In neonates, LBP + IL-6 improves early detection of sepsis.
  • Persistently high LBP suggests ongoing bacterial translocation (IBD, cirrhosis).

Interesting Fact

LBP is part of the innate immune system’s “first responder” team, rapidly mobilized to detect and neutralize endotoxin long before typical inflammatory markers rise.

References

  1. Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Acute Phase Reactants
  2. Mayo Clinic Laboratories - LBP
  3. ARUP Consult - Sepsis Biomarkers
  4. IDSA Guidelines - Sepsis & Endotoxemia
  5. Critical Care Reviews - LBP in Sepsis
  6. MedlinePlus / NIH - Inflammation Markers

Last updated: January 26, 2026

Reviewed by : Medical Review Board

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