Application
Diagnostic reasoning
Start with the bleeding phenotype and organize PT/aPTT before the differential.
Objective: Distinguish primary hemostasis, secondary hemostasis, global consumption, and inhibitors.
Suggested time: 12 min
Clinical library
Learn through modules, not an endless page
Choose an objective, study one block at a time, and use search to quickly locate tests, concepts, and diagnostic traps.
Active learning
Want to test yourself before reviewing?
The Clinical Bench guides you through hypothesis, test selection, interpretation, and targeted confirmation in six progressive cases.
Available modules
6 modules found
Application
Laboratory and preanalytics
Connect collection, citrate, processing, interference, and quality control to the result.
Objective: Decide whether a result represents the patient or a sample problem.
Suggested time: 15 min
Foundation
Hemostasis models
Compare the classic assay cascade with the cell-based model of in-vivo coagulation.
Objective: Know which question each model answers and avoid mixing them.
Suggested time: 10 min
Application
Platelets and microscopy
Review morphology, activation, and platelet participation in hemostasis.
Objective: Relate visual findings to primary hemostasis without overinterpreting images.
Suggested time: 10 min
Application
Multiprofessional care
Integrate clinical observation, safety, communication, and nursing care.
Objective: Recognize warning signs and communicate findings clearly.
Suggested time: 8 min
Reference
Glossary and factors
Look up technical terms and the role of each factor in the classic pathways.
Objective: Use a quick reference without losing functional context.
Suggested time: Open
Studying
Diagnostic reasoning
Distinguish primary hemostasis, secondary hemostasis, global consumption, and inhibitors.
Clinical reasoning
How to interpret PT, PTT, and bleeding pattern
Start with the clinical bleeding pattern, then connect laboratory tests to the most likely pathway in the cascade.
Mucocutaneous bleeding
Petechiae, purpura, epistaxis, gum bleeding, menorrhagia.
Suggests platelet, vascular, or von Willebrand-related problems.
Deep bleeding
Hemarthrosis, muscle hematomas, delayed post-trauma bleeding.
Suggests a coagulation factor deficiency.
Prolonged PT + normal PTT
Extrinsic pathway
Factor VII, early vitamin K deficiency, warfarin, or early liver disease.
Normal PT + prolonged PTT
Intrinsic pathway
Factors VIII, IX, XI, XII, heparin, or lupus anticoagulant.
Prolonged PT and PTT
Common pathway or global consumption
Factors X, V, II, I, DIC, liver disease, or severe vitamin K deficiency.
Normal PT and PTT with bleeding
Think beyond global tests
Platelets, von Willebrand disease, Factor XIII, or vascular abnormalities.
Practical rule
If only one test is abnormal, think about the corresponding pathway. If PT and PTT are both abnormal, look for common pathway disease or global factor consumption.
Important trap
Factor XIII can cause delayed bleeding with normal PT and PTT because it acts during stabilization of already formed fibrin.
Teaching limit
The classic cascade helps explain laboratory tests, but in vivo coagulation is more integrated and begins mainly through tissue factor.
Diagnostic approach
How to approach a patient with bleeding
A practical pathway from the clinical complaint to the most likely group of causes.
1. Define the bleeding pattern
Petechiae, purpura, and mucosal bleeding suggest platelets/von Willebrand. Hemarthrosis, deep hematomas, and delayed bleeding suggest coagulation factors.
Next step
2. Look for family history
Bleeding since childhood, affected male relatives, or familial recurrence increase suspicion for hemophilia and inherited disorders.
Next step
3. Review medications and context
Anticoagulants, antiplatelets, antibiotics, liver disease, sepsis, malnutrition, and recent surgery change test interpretation.
Next step
4. Interpret initial tests
Start with platelets, PT/INR, PTT, fibrinogen, and D-dimer. The combined pattern often points to the likely pathway or systemic process.
Next step
5. Direct the investigation
Abnormal PT suggests the extrinsic pathway. Abnormal PTT suggests the intrinsic pathway. Both abnormal suggests common pathway, consumption, or liver disease.
Next step
6. Remember exceptions
Normal PT/PTT does not exclude bleeding: assess platelets, von Willebrand, vascular disorders, and Factor XIII deficiency.
Mental summary: first classify the bleeding type, then check platelets/PT/PTT, and only then connect the pattern to a cascade pathway or systemic causes.