Coagulation Time Evaluation

Introduction to Coagulation Tests

The American Academy of Pediatrics recommends that the Prothrombin Time (PT) evaluates the extrinsic and common pathways (factors VII, X, V, II, and fibrinogen), while the Activated Partial Thromboplastin Time (APTT) evaluates the intrinsic and common pathways (factors XII, XI, IX, VIII, X, V, II, and fibrinogen) 1, 2
The International Society on Thrombosis and Haemostasis states that PT specifically evaluates factor VII (extrinsic pathway) and factors X, V, II, and fibrinogen (common pathway) 1, 2
The Journal of Thrombosis and Haemostasis notes that the INR is a standardization of PT designed exclusively for monitoring warfarin, not for evaluating general coagulopathies 3

The American Academy of Pediatrics indicates that APTT evaluates factors XII, XI, IX, VIII (intrinsic pathway) and factors X, V, II, and fibrinogen (common pathway) 1, 2
The International Society on Thrombosis and Haemostasis recommends that APTT can detect mild hemophilia only if specific levels of factor VIII or IX are measured, as APTT may be normal in mild deficiencies 1, 2
The Journal of Thrombosis and Haemostasis states that deficiencia aislada de factor VII is a cause of isolated PT prolongation 1, 2

The American Society of Anesthesiologists recommends that Fresh Frozen Plasma (FFP) is indicated when INR >2.0 with active microvascular bleeding 6
The American Society of Anesthesiologists suggests that the dose of FFP should be calculated to achieve a minimum 30% concentration of plasma factors 6
The British Thoracic Society recommends that platelets should be transfused if <50×10⁹/L with active surgical bleeding 6
The British Thoracic Society suggests that platelets should be transfused if <100×10⁹/L before invasive procedures 7

The Critical Care journal recommends that warfarina should be suspended immediately in cases of bleeding, and PFC should be administered if no concentrates of prothrombin complex are available 8
The Journal of Thrombosis and Haemostasis notes that heparina should be suspended, and protamina should be administered if active bleeding occurs 4

The British Thoracic Society recommends that safe thresholds for percutaneous lung biopsy are PT ratio or APTT ratio <1.4, and platelets >100×10⁹/L 7
The British Thoracic Society suggests that warfarina should be suspended 4 days before the procedure (time for INR <1.5) 7

The Journal of Thrombosis and Haemostasis warns that INR should not be used to evaluate coagulopathies not related to warfarina, as it lacks validity for liver disease, DIC, or acute bleeding 3
The Journal of Thrombosis and Haemostasis notes that factor XII deficiency prolongs APTT but does not cause bleeding, and therefore does not require correction 3
The Journal of Thrombosis and Haemostasis recommends that APTT may be falsely elevated by interference from residual anti-Xa DOACs, and that measurement should be delayed for 3 days after suspension 4