Coagulation:- part 3 – Critical Coagulation Tests

September 12, 2025Hematology Lab Tests

Table of Contents

Critical Coagulation Tests

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

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		>30 seconds
Thrombin time (TT)	17 to 25 seconds	14 to 19 seconds Varies from lab to lab	>30 to 35 seconds
Bleeding time (BT)	2 to 8 minutes	Duke method: 1 – 4 minutes Ivy method: 2 – 7 minutes	> 15 minutes
Clotting time (CT)	2 to 6 minutes Glass tube 10 to 15 minutes		>20 minutes (Lee-White ) Or no clot formation
Fibrinogen	2.0 to 4.0 g/L		<100 mg/dL
Fibrinogen degradation products (FDP)	< 10 mg/L	Negative at 1:4 dilution <10 mg/dL	Mild increase = 10 to 40 µg/mL Significant increase = 40 to 50 µg/mL Marked increase = >100 µg/mL
Plasma D-dimer	< 200 mg/L	<250 µg/L	>2.0 µg/mL or when 4.0 to 5.0 µg/mL
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 coagulation tests: Coagulation pathways

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

Question 1: What is the critical value of fibrinogen?

Question 2: What is the critical value of APTT?