What are the diagnostic criteria for disseminated intravascular coagulation (DIC)?

Diagnostic Criteria for Disseminated Intravascular Coagulation (DIC)

Use the ISTH overt DIC scoring system as the global standard for diagnosing decompensated DIC, requiring ≥5 points, and apply the SIC scoring system (≥4 points) for earlier detection in septic patients. 1, 2

ISTH Overt DIC Scoring System (≥5 Points = DIC)

The ISTH overt DIC criteria represent the gold standard for diagnosing decompensated DIC and require an underlying causative condition (sepsis, trauma, malignancy, obstetrical complications) plus laboratory confirmation. 1, 2

Scoring parameters:

• Platelet count:

  • <50 × 10⁹/L = 2 points 2
  • ≥50 to <100 × 10⁹/L = 1 point 2
  • ≥100 × 10⁹/L = 0 points 2

• Fibrin-related markers (D-dimer or FDP):

  • Strong increase = 3 points 2
  • Moderate increase = 2 points 2
  • No increase = 0 points 2

• Prothrombin time (PT):

  • ≥6 seconds prolonged OR PT ratio >1.4 = 2 points 2
  • ≥3 to <6 seconds prolonged OR PT ratio >1.2 to ≤1.4 = 1 point 2
  • <3 seconds prolonged = 0 points 2

• Fibrinogen level:

  • <100 mg/dL = 1 point 2
  • ≥100 mg/dL = 0 points 2

Total score ≥5 = overt DIC diagnosis 2

Sepsis-Induced Coagulopathy (SIC) Scoring System (≥4 Points = SIC)

The SIC scoring system detects the compensated phase of DIC in sepsis patients earlier than overt DIC criteria, with approximately 60% of septic patients meeting SIC criteria versus only 30% meeting overt DIC criteria. 1, 2 Almost all patients with overt DIC were diagnosed with SIC earlier in their disease course. 1

Scoring parameters:

• Platelet count:

  • <100 × 10⁹/L = 2 points 2
  • ≥100 to <150 × 10⁹/L = 1 point 2
  • ≥150 × 10⁹/L = 0 points 2

• PT ratio:

  • 1.4 = 2 points 2

  • 1.2 to ≤1.4 = 1 point 2

  • ≤1.2 = 0 points 2

• SOFA score:

  • ≥2 = 2 points (capped at 2 even if SOFA >2) 2
  • 1 = 1 point 2
  • 0 = 0 points 2

Total score ≥4 = SIC diagnosis 2

Algorithmic Approach to DIC Diagnosis

For septic patients, use a two-step algorithm: First assess for SIC; if SIC criteria are met (≥4 points), then evaluate for overt DIC (≥5 points). 2 This approach enables earlier detection and intervention, as SIC mortality is ≥30%, making it a clinically significant threshold for patient selection for anticoagulant therapy. 1, 2

For non-septic patients (trauma, malignancy, obstetrical complications), proceed directly to ISTH overt DIC scoring. 2

Critical Diagnostic Considerations

Fibrinogen interpretation varies by underlying condition: Hypofibrinogenemia is uncommon in sepsis-associated DIC due to excessive suppression of fibrinolysis, whereas malignancy-associated DIC demonstrates a fibrinolytic phenotype with more frequent bleeding and low fibrinogen. 2 This explains why fibrinogen is deliberately excluded from SIC criteria—it is usually normal or elevated in sepsis as an acute-phase reactant. 2

Dynamic monitoring is essential: DIC is a progressive syndrome that evolves from compensated to decompensated phases. 2 Repeat laboratory testing should track disease progression and treatment response, with declining trends in platelet count and fibrinogen being more diagnostically important than static values. 3

A 30% or greater drop in platelet count is diagnostic of subclinical DIC even when absolute platelet values remain in the normal range. 3

Ruling Out DIC

A normal D-dimer level effectively rules out DIC, as this test has the highest sensitivity (91-100%) among all laboratory markers. 3 However, normal PT and PTT do NOT rule out DIC, particularly in sepsis or subclinical cancer-associated DIC, where these tests may remain normal in approximately 50% of cases. 3

A score <5 points on ISTH overt DIC criteria effectively rules out overt DIC, and a score <4 points on SIC criteria rules out sepsis-associated coagulopathy. 3

Common Pitfalls to Avoid

Do not rely on fibrinogen level alone to grade DIC severity in sepsis—it is excluded from SIC criteria because it typically remains elevated as an acute-phase reactant. 2

Do not use a single laboratory test to diagnose or exclude DIC—no single test is sufficiently accurate, which is why combination scoring systems are required. 4

Do not assume all DIC presents identically—different underlying conditions (sepsis, malignancy, trauma) produce distinct coagulation phenotypes with varying degrees of thrombosis versus bleeding. 2