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Coagulation:- part 3 – Coagulation Screening Tests, and Critical values

September 15, 2023HematologyLab Tests

Table of Contents

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  • Coagulation Screening tests
      • For the screening of coagulation abnormality, the following tests are advised.
        • The tests advised for coagulation screening workup and critical (panic) values:
      • Critical values of blood coagulation screening test:
        • Differential diagnoses of bleeding disorders:
      • Questions and answers:

Coagulation Screening tests

For the screening of coagulation abnormality, the following tests are advised.

  1. Platelets count  (140,000 to 340,000 /cmm).
  2. Bleeding time  (Ivy method <4 min and Duke method 1 to 4 min).
  3. Clot retraction qualitative begins in 30 to 60 minutes, completed within 24 hours but usually within 6 hours.
  4. Coagulation time or clotting time (5 to 15 minutes in glass tubes and 19 to 60 minutes in the siliconized tube).
  5. Fibrinolysins are negative.
  6. Prothrombin time, one stage  (same as control and should be 11 to 16 seconds).
  7. Thromboplastin generation time (compared to normal control).
  8. To measure  the intrinsic system, advise:
    1. Activated partial thromboplastin APTT.
  9. To measure the extrinsic system, advise:
    1. One stage prothrombin time PT.

The tests advised for coagulation screening workup and critical (panic) values:

Test           Normal values    Normal values source (4)  Critical values   (source 3)
Platelets count 150.000 to 450,000 /cmm <100,000   (20,000 /cmm)
Activated partial thromboplastin time (APTT)           25 to 35 seconds >40 seconds.
Prothrombin time  (PT)            10 to 13 seconds >15 seconds
Thrombin time  (TT)            17 to 25 seconds
Bleeding time (BT)            2 to 8 minutes
Clotting time (CT) 2 to 6 minutes (glass tube 10 to 15 minutes)
Fibrinogen            2.0 to 4.0 g/L <100 mg/dL
Fibrinogen degradation products (FDP)           < 10 mg/L
  1. Negative at 1:4 dilution
  2. <10 mg/dL
Plasma D-dimer            < 200 mg/L <250 µg/L
Coagulation factors              500 to 1500 U/L
Factor V% <35%
Factor VII <10%
Factor VIII <100%  and >160%
Factor IX <30%
Protein C              70 to 1400 U/L
Protein S total             70 to 1400 U/L

Critical values of blood coagulation screening test:

  •  Platelets = <50,000/cmm or > 1 million/cmm.
  • APTT        = >70 seconds.
  • PTT          = >100 seconds.
  • Fibrinogen = <100 mg/dL.
Coagulation screening tests: Coagulation pathways

Coagulation screening tests: Coagulation pathways

Differential diagnoses of bleeding disorders:

APTT PT Platelets count Causes of bleeding disorders
Increased Normal Normal
  1. Heparin therapy
  2. Factor VIII, IX, and XI deficiencies
  3. Lupus anticoagulant
  4. von Willibrand’s disease
Normal Increased Normal
  1. Early coumadin therapy
  2. Factor VII deficiency or inhibitor
  3. Early vitamin K deficiency
  4. Early liver diseases
Increased Increased Normal
  1. Heparin therapy
  2. Coumadin therapy
  3. Malabsorption
  4. Liver diseases
  5. DIC (acute)
  6. Gall bladder diseases
Normal Normal Normal
  1. Chronic compensated DIC
  2. von Willebrand’s disease
  3. Factor XIII deficiency
  4. Aspirin
  5. Uremia
  6. Fibrinogen disorder (dysfibrinogenemia)
  7. Vasculitis
  8. Scurvy
  9. Colonic carcinoma
Normal Normal Increased
  1. Proliferative disorders
  2. CML
  3. Polycythemia rubra vera
  4. Essential thrombocythemia
Normal Normal Decreased
  1. Hemodilution
  2. Platelet disorders (destruction)
Increased Increased Decreased
  1. Acute DIC
  2. Liver diseases
  3. Heparin-induced thrombocytopenia
  4. Hypersplenism
  5. Thrombotic thrombocytopenic purpura
  6. Hemolytic uremic syndrome

Questions and answers:

Question 1: What is the critical value of fibrinogen?
Show answer
Fibrinogen critical value is <100 mg/dL.
Question 2: What is the critical value of APTT?
Show answer
APTT critical value is >70 seconds.

Possible References Used
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