How is disseminated intravascular coagulation diagnosed?

Diagnosis of Disseminated Intravascular Coagulation

Diagnose DIC using the ISTH overt-DIC scoring system, which requires a score ≥5 points calculated from platelet count, PT prolongation, elevated fibrin markers (D-dimer/FDP), and fibrinogen level—but only in patients who have an appropriate underlying trigger such as sepsis, trauma, malignancy, or obstetric complications. 1, 2

Mandatory Prerequisite for Diagnosis

• DIC cannot be diagnosed by laboratory tests alone—you must first identify an underlying disorder known to cause DIC, as DIC is a mechanistic process rather than a primary disease entity. 3
• The most common triggers are sepsis (most frequent overall), trauma, hematologic malignancies, solid tumors, obstetric complications (placental abruption, amniotic fluid embolism), major surgery, and burns. 2, 3

ISTH Overt-DIC Scoring System (Gold Standard)

Calculate the score using these four components: 1, 2

Platelet Count

• 2 points if <50 × 10⁹/L
• 1 point if ≥50 but <100 × 10⁹/L
• 0 points if ≥100 × 10⁹/L 1

Fibrin Markers (D-dimer or FDP)

• 3 points for strong increase (typically >5× upper limit of normal)
• 2 points for moderate increase (typically 2-5× upper limit of normal)
• 0 points for normal or mild elevation 1

Prothrombin Time Prolongation

• 2 points if PT prolonged ≥6 seconds above control (or PT ratio >1.4)
• 1 point if PT prolonged ≥3 but <6 seconds (or PT ratio >1.2 but ≤1.4)
• 0 points if PT prolonged <3 seconds 1, 2

Fibrinogen Level

• 1 point if <100 mg/dL (1 g/L)
• 0 points if ≥100 mg/dL 1

A total score ≥5 confirms overt DIC. 1, 2

Two-Step Sequential Approach for Septic Patients

The ISTH recommends screening septic patients in two stages to catch coagulopathy earlier when intervention may be most beneficial: 1, 4

Step 1: Screen with Sepsis-Induced Coagulopathy (SIC) Criteria

Apply SIC scoring to any septic patient with platelet count <150 × 10⁹/L: 1, 4

• Platelet count: 2 points if <100 × 10⁹/L; 1 point if ≥100 but <150 × 10⁹/L
• PT ratio: 2 points if >1.4; 1 point if >1.2 but ≤1.4
• SOFA score: 2 points if ≥2; 1 point if =1 (use sum of respiratory, cardiovascular, hepatic, and renal SOFA components) 1

A score ≥4 indicates SIC (compensated phase of DIC). 1

Step 2: Assess for Overt DIC

If SIC criteria are met, immediately calculate the ISTH overt-DIC score using the full scoring system above. 1

Clinical rationale: SIC represents an earlier, compensated phase that typically precedes overt DIC, and mortality among SIC patients is ≥30%. Nearly all patients who develop overt DIC had previously met SIC criteria, making early detection critical. 1, 4

Essential Laboratory Tests

Order these tests when DIC is suspected: 2, 3, 5

• Complete blood count with platelet count—a ≥30% drop in platelets is diagnostic of subclinical DIC even when absolute values remain normal 2
• Prothrombin time (PT) and activated partial thromboplastin time (aPTT)—may be prolonged, though normal values do not exclude DIC 2, 5
• Fibrinogen level—typically decreased due to consumption in advanced DIC, but may be normal or elevated early in sepsis due to acute-phase response 2, 4
• D-dimer or fibrin degradation products (FDP)—elevated, indicating ongoing fibrinolysis; D-dimer is highly sensitive for DIC 2, 5, 6
• Peripheral blood smear—look for schistocytes (fragmented red cells) indicating microangiopathic hemolysis from microvascular thrombosis 4

Dynamic Monitoring is Critical

Single laboratory values are insufficient—trend analysis over hours to days is more diagnostically important than absolute values: 1, 2

• Daily monitoring for acute severe DIC with active bleeding or rapid clinical deterioration 2
• Every 2-3 days for stable ICU patients with diagnosed DIC 2
• Repeat screening on day 2 of ICU admission if initial screening was positive, as this strengthens mortality prediction 1

Serial measurements help differentiate true DIC (which shows dynamic worsening) from stable chronic coagulopathy (e.g., cirrhosis), where laboratory values remain relatively constant. 1

Special Diagnostic Considerations

Differentiating DIC from Cirrhotic Coagulopathy

This is challenging because laboratory abnormalities overlap extensively. 1

• In cirrhosis, coagulation parameters are typically stable over time, whereas DIC shows dynamic deterioration 1
• Serial testing is essential—rapid changes in platelet count, PT, and fibrinogen suggest DIC superimposed on chronic liver disease 1
• Soluble fibrin is expected to be a more specific marker for DIC, though its performance requires further validation 1
• Low antithrombin levels can help distinguish DIC (consumption) from isolated liver disease, though both conditions may have decreased antithrombin 2

Recognizing DIC Subtypes

The clinical presentation varies by underlying cause: 2

• Procoagulant (thrombosis-predominant) DIC: Common in pancreatic cancer and adenocarcinomas; presents with arterial ischemia, venous thromboembolism, or microvascular thrombosis 2
• Hyperfibrinolytic (bleeding-predominant) DIC: Typical of acute promyelocytic leukemia and metastatic prostate cancer; presents with widespread bleeding from multiple sites 2
• Subclinical DIC: Diagnosed by ≥30% platelet drop, elevated D-dimer, and mild coagulation factor consumption; may progress to overt DIC without treatment of the underlying condition 2

Common Diagnostic Pitfalls

• Do not rely on fibrinogen alone—it may be normal or even elevated early in sepsis-associated DIC because fibrinogen is an acute-phase reactant 2, 4
• Do not exclude DIC based on normal PT/aPTT—these may remain normal in early or chronic DIC 2, 5
• Do not diagnose DIC without an appropriate clinical trigger—laboratory abnormalities alone are insufficient 3, 5
• Do not use a single time-point—DIC is a dynamic process requiring serial assessment 1, 5
• Beware of symmetrical peripheral gangrene (SPG)—a devastating complication of sepsis-associated DIC causing acral limb loss from microvascular thrombosis, often preceded by acute hepatic dysfunction ("shock liver") that depletes natural anticoagulants 1, 4