At a Glance

Why It's Ordered
Suspected disseminated intravascular coagulation (DIC) with bleeding or clotting in sepsis, major trauma, obstetric hemorrhage or malignancy, where the score decides whether to treat the trigger and replace components.
Check First
Platelets, PT/INR, fibrinogen and D-dimer together: the four ISTH score items. A long PT with low fibrinogen and a high D-dimer points to consumption; one value alone does not diagnose DIC.
Critical Values
Lab critical values (typical, lab-dependent): Platelets <30 ×10³/µL · Fibrinogen <100 mg/dL · INR >5.0 · aPTT ≥100 s. Call-now threshold (not a lab critical value): ISTH overt DIC score ≥5
Don't Miss
Giving 4F-PCC to a patient with DIC: the label contraindicates it. Treat the trigger, replace components by bleeding and measured level, and involve hematology early.
Field & Transport
A fingerstick INR is approximate and no EMS kit measures the full score. Send a light-blue citrate tube and a lavender tube with the draw time, and hand over the trend and every product given.

Panel Overview

The DIC panel is five tests: platelet count, prothrombin time with INR (PT/INR), activated partial thromboplastin time (aPTT), fibrinogen and D-dimer. Together they produce the ISTH overt disseminated intravascular coagulation (DIC) score, which applies only when a DIC trigger is present, such as sepsis, major trauma, obstetric hemorrhage or malignancy. Platelets, PT/INR and fibrinogen also appear on the CBC and coagulation pages. This panel adds the score and the decisions it drives.

When to Order:
  • Sepsis or shock with bleeding: oozing from lines, purpura or hematuria
  • Major trauma: hemorrhagic shock or massive transfusion
  • Obstetric emergency: placental abruption, postpartum hemorrhage or suspected amniotic fluid embolism
  • Malignancy: bleeding in acute promyelocytic leukemia or another hematologic cancer
  • Liver failure: bleeding or a clotting profile that does not match the liver disease
  • Thrombosis with a falling platelet count: also consider heparin-induced thrombocytopenia

Clotting Times

PT/INR

Normal: PT 11–13.5 s | INR 0.8–1.1

Extrinsic and common pathways. Prolonged in DIC, liver failure, warfarin and vitamin K deficiency. Scored as PT prolongation above the laboratory upper limit of normal in the ISTH score (3 to under 6 s is 1 point; 6 s or more is 2).

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aPTT

Normal: 25–35 s

Intrinsic and common pathways. Prolonged in DIC, heparin exposure, lupus anticoagulant and factor deficiency. Not one of the four ISTH score items; read it with PT to see the pattern.

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Consumption & Fibrin Markers

Fibrinogen

Normal: 200–400 mg/dL

Clot substrate. Falls with consumption, dilution and fibrinolysis; scored below 100 mg/dL. Pregnancy and inflammation raise it, so a low-normal value can still mean consumption.

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D-dimer

Normal: <500 ng/mL FEU

Fibrin breakdown product, scored as a multiple of the upper limit of normal. High in DIC but also in PE, DVT, trauma and age over 50, so it is never read alone.

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Platelets

Platelet Count

Normal: 150–450 ×10³/µL

Scored at under 100 and under 50 ×10³/µL. The DIC pattern is consumption with a falling count. Smear the blood before transfusing to exclude TTP, HUS or HIT.

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Calculated Values

ISTH Overt DIC Score

Expected: 0–4 points (no overt DIC)

Sum of platelet, D-dimer, PT and fibrinogen points (maximum 8). 5 or more is consistent with overt DIC. Repeat and trend the score; a single value is not diagnostic.

Common Add-Ons

Hemoglobin

Normal: M 13.5–17.5 | F 12.0–16.0 g/dL

Falls with ongoing hemorrhage, and early values can lag the true blood loss. Trend it with the score and with transfusion decisions.

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Peripheral Smear

Expected: no schistocytes

Look for schistocytes and clumped platelets. Schistocytes point to a microangiopathy (TTP, HUS, HELLP) rather than simple DIC; review with the laboratory and hematology.

Reference Ranges & Critical Values
Lab-specific ranges: Your lab's numbers are the ones that count. Intervals and critical lists change with the lab, the analyzer and the assay. Use the interval your lab reports and follow its critical-call policy.
TestAdult Normal (conventional)SI UnitsCritical LowCritical HighNotes
Platelets
150–450 ×10³/µL
150–450 ×10⁹/L
<30
>1,000
Scores 2 below 50 and 1 at 50 to under 100
PT
11–13.5 s
11–13.5 s
—
—
Reagent-specific; use lab range
INR
0.8–1.1
Dimensionless
—
>5.0
Warfarin 2.0–3.0; 2.5–3.5 mechanical mitral
aPTT
25–35 s
25–35 s
—
≥100 s
Lab-calibrated; typical critical value
Fibrinogen
200–400 mg/dL
2–4 g/L
<100 mg/dL
—
Scores 1 below 100 mg/dL (1 g/L)
D-dimer
<500 ng/mL FEU
<500 µg/L FEU
—
—
Score uses multiples of the lab upper limit
ISTH overt DIC score
0–4 points
Not applicable
—
Call-now threshold: ≥5 points
Score, not a lab value; repeat and trend

Think of these critical values as typical. Your institution sets the real ones. Pediatric ranges are in Special Populations.

Systematic Interpretation
  1. Name the trigger: Ask what started it. Sepsis, trauma, obstetric emergency, malignancy, liver disease, transfusion or heparin exposure. The score applies only to a patient with a DIC-associated condition.
  2. Draw the four score tests together: Platelets, PT/INR, fibrinogen and D-dimer. Citrate tube first, before any line flush.
  3. Score the ISTH criteria: Work through the formula box. 5 or more is consistent with overt DIC.
  4. Classify the phenotype: Bleeding dominates (hemorrhagic) or clots dominate (thrombotic). That call steers heparin and component decisions with hematology.
  5. Exclude mimics: Schistocytes, or a neurologic or renal picture (TTP, HUS, HELLP). A platelet fall after heparin points to HIT. A PT and aPTT pattern driven by an anticoagulant is not consumption.
  6. Trend: Every clinical draw gets the score and the four tests again. Rising D-dimer with falling fibrinogen and platelets: consumption is getting worse.
ISTH overt DIC score (2025 update; D-dimer thresholds per 2025, other items per 2001 weights pending full-text check)
Platelet points + D-dimer points + PT points + fibrinogen points (maximum 8)

Platelets: under 50 ×10³/µL = 2; 50 to under 100 = 1; 100 or more = 0. D-dimer: over 7× upper limit = 3; over 3× = 2; otherwise 0. PT prolongation above the laboratory upper limit of normal: 6 s or more = 2; 3 to under 6 s = 1; under 3 s = 0. Fibrinogen: under 100 mg/dL (1 g/L) = 1; otherwise 0. Interpretation: 5 or more = consistent with overt DIC; under 5 = not overt DIC, repeat the score.

Verification note: The platelet, PT and fibrinogen weights are the long-standing ISTH ones. Check them against the 2025 ISTH table before you lean on them.

Worked Example: Picture a septic patient. Platelets 42 ×10³/µL earn 2 points. D-dimer at 9× the upper limit earns 3. PT of 17 s, against a 13.5 s upper limit of normal, is 3.5 s prolonged: 1 point. Fibrinogen 92 mg/dL adds 1. The total of 7 is consistent with overt DIC. Treat the sepsis source. Replace components by bleeding and measured deficit per protocol. Bring in hematology.

Patterns & Differential

Read each pattern against the patient in front of you. One result can have several causes.

PatternKey FindingsCommon CausesNext Step
Overt DIC (score 5 or more)
Low platelets, long PT, low fibrinogen, high D-dimer
Sepsis, trauma, placental abruption, amniotic fluid embolism, malignancy, liver failure
Treat the trigger; replace components by measured deficit and bleeding
Early-phase DIC (score under 5)
One or two abnormal tests, or a falling trend
Early sepsis, cancer, pregnancy, trauma
Repeat the score; treat the cause; no blood products unless bleeding
Thrombotic phenotype
New clot at a new site; fibrinogen may be near normal
Sepsis and malignancy with consumption
Hematology now; anticoagulation weighs bleeding risk
Hemorrhagic phenotype
Major bleeding with a score of 5 or more
Massive transfusion, trauma, acute promyelocytic leukemia
Replace by bleeding and measured level; antifibrinolytics only in hyperfibrinolysis
Isolated prolonged PT/INR
Normal platelets and fibrinogen
Warfarin, DOAC, vitamin K deficiency, liver disease
Reversal per the anticoagulant reversal page
Low platelets with schistocytes
PT and aPTT often normal; neurologic or renal signs
TTP, HUS, HELLP
Smear; urgent hematology; ADAMTS13 per laboratory
Platelet fall after heparin
Fall of more than 50% on day 5–10 of heparin
Heparin-induced thrombocytopenia (HIT)
Stop all heparin including flushes; 4Ts score and PF4 per platelets page
High D-dimer, normal platelets and fibrinogen
Clinical picture decides
Pulmonary embolism, DVT, aortic dissection, recent surgery, pregnancy
Pretest probability first; PE pathway (see pulmonary embolism page)

Serial Testing & Kinetics
AnalyteRises/DetectablePeaksReturns to Baseline / Repeat IntervalMonitoring Target
Platelets
Falls early with consumption
Lowest during active bleeding
Recovers as the trigger is treated; repeat with each score
Keep above 50 ×10³/µL with ongoing bleeding (platelets page)
Fibrinogen
Falls as it is consumed; acute-phase rise can mask it
Lowest during bleeding
Recheck after each replacement dose
Replace by bleeding and the thresholds on the fibrinogen page
D-dimer
Rises with fibrin turnover
Varies with the trigger
Trend, not a single value
Falling trend as the trigger resolves
PT/INR
Prolongs with factor consumption
Varies with the trigger
Repeat with each score
PT moving back toward normal
ISTH score
5 or more points = overt DIC
Varies with the trigger
Repeat on each lab draw
Score falling below 5 as the trigger is controlled

Critical Findings & Emergency Actions

Overt DIC with active bleeding

Recognize: A score of 5 or more, and the patient is oozing from lines, passing blood in the urine or hemorrhaging. Sepsis, trauma or obstetric bleeding is the setting.

  1. Treat the trigger (Paramedic/RN): hemorrhage control and source control per the medical team; obstetric delivery decisions per the obstetric team.
  2. Replace by measured deficit, not empirically (RN): Fibrinogen follows the fibrinogen page. Platelets follow the platelets page. AABB 2025 suggests transfusion below 10 ×10³/µL for consumptive thrombocytopenia without major bleeding (conditional).
  3. Components for bleeding: In general, save platelets and plasma for the patient who is bleeding. The 2013 harmonized ISTH guidance says so. Non-bleeding patients at high risk of bleeding are managed per hematology and local protocol.
  4. Antifibrinolytics: generally avoided in DIC. The exception is severe bleeding in a markedly hyperfibrinolytic state, such as trauma or leukemia. In bleeding trauma, don't delay protocol tranexamic acid. DIC alone is not a reason to withhold it, per trauma protocol and medical direction. Outside trauma, give it only under the local protocol for that setting.

Bleeding on an anticoagulant with DIC

Recognize: Major bleeding on warfarin or a DOAC. The patient also meets DIC criteria.

  1. Do not give 4-factor PCC: 4F-PCC (Kcentra) is contraindicated in DIC and in heparin-induced thrombocytopenia.
  2. Use the reversal pathway: Follow the anticoagulant reversal page and per-protocol medical direction. Non-PCC options: warfarin, IV vitamin K with plasma. Dabigatran, idarucizumab. Factor Xa inhibitors, andexanet alfa where still available (check current US status on the reversal page). Heparin, protamine. Get hematology involved early.
  3. Check the last dose and renal function and label the time drawn on every specimen.

Critically ill, not bleeding, with DIC

Recognize: The score sits at 5 or more, yet nothing is actively bleeding and no clinically important thrombosis is present.

  1. Prophylactic heparin: For critically ill non-bleeding patients with DIC, the 2013 harmonized ISTH guidance recommends prophylactic-dose heparin to prevent venous thromboembolism. High-alert Heparin dose and monitoring per the heparin page and protocol.
  2. Therapeutic heparin: this is for when clots dominate and bleeding risk is low, per hematology.
  3. Avoid prophylactic transfusion: In DIC, platelets and plasma are in general for bleeding. Non-bleeding patients at high bleeding risk are managed per hematology and local protocol.
  4. Other agents: Antithrombin or recombinant thrombomodulin may be considered in certain patients with DIC, per hematology. Availability is not uniform.

Platelet fall after heparin

Recognize: Platelets drop during or after heparin exposure. Thrombosis may or may not be present.

  1. Stop all heparin: infusions, flushes, lock solutions and heparin-coated catheters, per local protocol.
  2. Score and test: 4Ts score and PF4 immunoassay per the platelets page; consider a non-heparin anticoagulant per hematology.
  3. Warning: The PCC product itself contains heparin, so HIT rules it out.

Prehospital & Transport Considerations

Point-of-Care Testing

Device / MethodAnalytesSpecimenLimitations
Fingerstick POC INR
PT/INR
Capillary
Approximate; less reliable at high INR and with antiphospholipid antibodies; confirm on laboratory blood
Viscoelastic testing (TEG or ROTEM)
Clot strength and fibrinolysis
Whole blood
Hospital-based; assay-specific with no universal range
Platelets, fibrinogen, D-dimer
Laboratory tests
Lavender and light blue
Not in standard EMS kits; send to the laboratory with the time drawn

Interfacility Transfer & Handoff

  • Results and times: the four score tests, the time drawn, and any score calculated.
  • Replacement history: each fibrinogen, platelet and plasma dose with its time, and the result after it.
  • Pending items: type and crossmatch, smear review, and PF4 if HIT is suspected.
  • Trend: One value tells them little. The receiving team needs the series.

Scope Notes

  • Blood product and anticoagulant decisions follow the local protocol and medical direction.
  • Transport teams don't start empiric component therapy outside the protocol.

Special Populations

Pediatrics

In children, DIC is most often sepsis or trauma. Use the lab's age-specific ranges for the four score tests. Don't apply adult values to neonates. AABB 2025 suggests platelet transfusion below 25 ×10³/µL for consumptive thrombocytopenia in neonates without major bleeding (strong recommendation). Pediatric sepsis lives on the pediatric sepsis page. Fibrinogen dosing by weight is on the fibrinogen medication page.

Pregnancy

Fibrinogen and D-dimer climb in normal pregnancy. A value that looks normal can still be consumption. A pregnancy-modified ISTH score drops D-dimer and scores platelet count, PT and fibrinogen alone. Ask the laboratory and obstetric team which version applies. The main obstetric DIC triggers are placental abruption, amniotic fluid embolism and postpartum hemorrhage. The postpartum hemorrhage page covers the obstetric workflow.

Older Adults

The age-adjusted D-dimer cutoff (age × 10 over 50) belongs to the pulmonary embolism pathway. It has no place in the ISTH DIC score, which uses multiples of the laboratory upper limit.

Liver Disease

Chronic liver disease cuts clotting factor production. So PT and fibrinogen run abnormal at baseline. Compare against the patient's own baseline before you score a new change.

Hematologic Malignancy

Acute promyelocytic leukemia is a DIC emergency with hyperfibrinolysis. It needs urgent hematology involvement. It is outside EMS scope.

Specimen Collection & Interfering Factors
  • Tube: light-blue citrate for PT/INR, aPTT, fibrinogen and D-dimer, filled to the line (9:1 blood to citrate). Lavender for the platelet count (tube colours are institution-dependent).
  • Order of draw: blood cultures, then light blue, red or gold, green, lavender, gray (CLSI GP41).
  • Site: fresh venipuncture, not from a line used for heparin or flushes, and not above an IV.
  • Handling: Delays change factor activity, so label the time drawn and send promptly.
Error / InterferentEffect on ResultsPrevention
Heparin contamination
Prolonged aPTT and unreliable PT
Draw from a fresh site, discard the line volume per protocol
Underfilled citrate tube
Falsely prolonged PT and aPTT
Fill to the line
EDTA contamination or clumping
Falsely low platelet count
Redraw in citrate or review the smear before transfusing
Delayed processing
Factor activity falls
Analyze promptly
D-dimer units mixed (DDU vs FEU)
Wrong rule-out or score
Use the laboratory's validated cutoff; never convert at the bedside

Clinical Pearls
Treat the trigger first: DIC resolves when its cause does. Source control and hemorrhage control come first. Components follow, per the 2013 harmonized ISTH guidance.
Normal does not mean normal: Fibrinogen usually runs high in late pregnancy and in sepsis. A value sliding toward the lower limit can be consumption.
The score needs a trigger: The 2025 ISTH criteria are built around underlying conditions. Bleeding with no DIC-associated condition? That patient needs a different workup.
Replace by measured deficit: Measured levels and bleeding set the dose for fibrinogen and platelets. Not a guess. Recheck after each dose.
Heparin is thrombosis-led: Clots lead the decision. Therapeutic heparin is considered when clots dominate and bleeding risk is low. Prophylaxis fits the non-bleeding critically ill patient.
Field and transport: A fingerstick INR gives you an approximate number. Send citrate blood for the score tests. Write the draw time on every tube.
Nursing: Trend platelets and fibrinogen after each product. A rising count means the product worked. A flat count means consumption is still going on.
Critical care: ICU patients often carry a high D-dimer. The score combines four results. One high value is not DIC.
Pitfall: 4F-PCC in DIC. Kcentra is contraindicated in DIC and in heparin-induced thrombocytopenia. Before you reverse warfarin in a patient with DIC, check the reversal page.
Pitfall: antifibrinolytic by reflex. Tranexamic acid is generally avoided in DIC. The exception is severe hyperfibrinolytic bleeding, such as trauma or leukemia. In bleeding trauma, run the trauma protocol for TXA. Don't hold it back because of DIC. Don't give it automatically to every bleeding patient with sepsis.

Related

References
  1. Iba T, Levy JH, Maier CL, et al. Updated definition and scoring of disseminated intravascular coagulation in 2025: communication from the ISTH SSC Subcommittee on Disseminated Intravascular Coagulation. J Thromb Haemost. 2025;23(7):2356–2362. https://doi.org/10.1016/j.jtha.2025.03.038
  2. Iba T, Maier CL, Scarlatescu E, Levy JH, et al. Introducing the new definition and diagnostic criteria of disseminated intravascular coagulation released by the International Society on Thrombosis and Haemostasis in 2025. Semin Thromb Hemost. 2026;52(1):10–17. https://doi.org/10.1055/a-2675-6068
  3. Wada H, Thachil J, Di Nisio M, et al. Guidance for diagnosis and treatment of DIC from harmonization of the recommendations from three guidelines (landmark guidance, 2013). J Thromb Haemost. 2013;11:761–767. https://doi.org/10.1111/jth.12155
  4. Metcalf RA, Nahirniak S, Guyatt G, et al. Platelet transfusion: 2025 AABB and ICTMG international clinical practice guidelines. JAMA. 2025;334(7):606–617. https://doi.org/10.1001/jama.2025.7529
  5. Kcentra (prothrombin complex concentrate, human) prescribing information. CSL Behring; revised 05/2023. DailyMed. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=eee1afb8-324c-42e4-8bf0-f0c9da5e6d42
  6. Clinical and Laboratory Standards Institute. GP41: Collection of Diagnostic Venous Blood Specimens, 7th ed. Wayne, PA: CLSI; 2017. Order of draw guidance.

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