Reptilase Time Test
Reptilase Time (RT)
Key Points
- Specialized coagulation test evaluating fibrinogen function
- Directly assesses the final common pathway of coagulation
- Complements prothrombin time (PT) and thrombin time (TT)
- Useful for diagnosing certain congenital and acquired fibrinogen disorders
Overview
Reptilase Time (RT) is a laboratory test that specifically measures the clotting time of plasma in the presence of reptile-derived thrombin-like enzyme. It bypasses the initial steps of the coagulation cascade and directly evaluates the conversion of fibrinogen to fibrin, providing insights into the functionality of the final common pathway.
Mechanism of Action
- Reptilase is a thrombin-like serine protease enzyme
- Derived from the venom of certain snakes
- Activates fibrinogen in a manner similar to thrombin
- Reptilase Time measurement
- Citrated plasma is incubated with reptilase reagent
- Time to visible clot formation is recorded
- Reflects the functional capacity of fibrinogen
- Technical Considerations
- Temperature-controlled environment
- Standardized reagents and methodology
- Potential interference from heparin or fibrin degradation products
Primary Applications
- Diagnosis of congenital fibrinogen disorders
- Afibrinogenemia
- Hypofibrinogenemia
- Dysfibrinogenemia
- Evaluation of acquired fibrinogen abnormalities
- Liver disease
- Disseminated intravascular coagulation (DIC)
- Consumptive coagulopathies
- Assessment of fibrinogen function
- Monitoring replacement therapy
- Preoperative bleeding risk stratification
- Thrombotic disorder investigations
Complementary Testing
- Prothrombin Time (PT)
- Evaluates the extrinsic and common coagulation pathways
- Helps distinguish fibrinogen disorders from other factor deficiencies
- Thrombin Time (TT)
- Measures the conversion of fibrinogen to fibrin
- Provides additional information on fibrinogen quality and function
- Fibrinogen Antigen (Fg:Ag)
- Quantifies the total amount of fibrinogen present
- Aids in differentiating between quantitative and qualitative fibrinogen defects
Age-Specific Reference Ranges
- Neonates (0-30 days)
- RT: 14-22 seconds
- Infants (1-12 months)
- RT: 13-20 seconds
- Children (1-16 years)
- RT: 12-19 seconds
Developmental Factors
- Physiological changes in fibrinogen levels with age
- Higher baseline in neonates and infants
- Gradual normalization to adult ranges
- Influence of hormonal changes during puberty
- Importance of using age-appropriate reference intervals
Interpretation of Reptilase Time
- Prolonged Reptilase Time
- Congenital fibrinogen disorders
- Afibrinogenemia
- Hypofibrinogenemia
- Dysfibrinogenemia
- Acquired fibrinogen abnormalities
- Liver disease
- Disseminated intravascular coagulation (DIC)
- Severe consumptive coagulopathies
- Presence of fibrin degradation products (FDPs)
- Congenital fibrinogen disorders
- Normal Reptilase Time
- Excludes primary fibrinogen disorders
- Does not rule out other coagulation factor deficiencies
Clinical Correlation
- Interpret results in the context of clinical presentation
- Consider potential confounding factors
- Medications (e.g., heparin, fibrinolytics)
- Sample handling and processing issues
- Concurrent medical conditions
- Integrate with other coagulation test results
- PT, TT, Fg:Ag, and specific factor assays
- Multifaceted approach to diagnose fibrinogen disorders
