Basic Coagulopathy Screen Components
A basic coagulopathy screen should include prothrombin time (PT/INR), activated partial thromboplastin time (aPTT), platelet count, and fibrinogen level 1, 2, 3, 4.
Core Laboratory Tests
The essential components of a coagulopathy screen are:
- Prothrombin Time (PT) or International Normalized Ratio (INR) - Assesses the extrinsic and common coagulation pathways
- Activated Partial Thromboplastin Time (aPTT) - Evaluates the intrinsic and common coagulation pathways
- Platelet Count - Identifies thrombocytopenia
- Fibrinogen Level - Detects hypofibrinogenemia, particularly important in bleeding patients
These four tests constitute the standard monitoring approach recommended by the American Society of Anesthesiologists for perioperative coagulopathy management 1. The European trauma guidelines similarly emphasize these parameters as routine practice for detecting post-traumatic coagulopathy 2.
Additional Considerations for Specific Clinical Contexts
In Bleeding or Trauma Patients
When evaluating a bleeding patient, the basic screen should also include hematocrit to assess blood loss 4. For trauma patients specifically, monitoring should extend to metabolic parameters like base deficit and lactate levels, as these correlate with shock severity and coagulopathy risk 2.
In Sepsis-Associated Coagulopathy
For patients with sepsis, the basic screen takes on additional diagnostic significance. The ISTH sepsis-induced coagulopathy (SIC) scoring system uses platelet count, PT ratio, and Sequential Organ Failure Assessment (SOFA) score, with a score ≥4 indicating SIC 3. D-dimer levels, while not part of routine screening, may help identify patients at higher thrombotic risk when markedly elevated (>6× upper limit of normal) 5.
Important Limitations to Recognize
PT/INR and aPTT alone should NOT be used to guide hemostatic therapy 1. These tests only monitor the initiation phase of coagulation (representing approximately 4% of thrombin production) and can appear normal while overall coagulation remains abnormal 2. This is a critical pitfall—normal screening tests do not exclude all coagulation disorders.
Tests NOT Part of Basic Screening
The following are not included in a basic coagulopathy screen but may be indicated based on clinical suspicion:
- Thrombin time (TT) - Used when heparin contamination or specific factor inhibitors are suspected 6
- Bleeding time or PFA-100 - For suspected platelet dysfunction, though these have limited sensitivity 7, 8
- D-dimer - Not a screening test; used for specific indications like DIC diagnosis or thrombotic risk stratification 3
- Viscoelastic testing (TEG/ROTEM) - May assist in characterizing coagulopathy but not part of basic screening 1, 2
- Specific factor assays - Second-line tests performed only when screening tests are abnormal or clinical suspicion is high 8, 9
Critical Clinical Context
The most powerful tool for detecting coagulopathy is the patient's bleeding history 9, 10. Screening tests performed without clinical indication (based on history, physical examination, or specific risk factors) are unnecessary and should not be done 10. In one prospective study, 46% of screening coagulation tests could have been eliminated by using clinical indications rather than routine screening 10.
The basic screen is designed to detect common, clinically significant coagulopathies but has "blind spots"—it will miss defects in fibrin network formation, fibrinolysis disorders (like alpha-2-antiplasmin deficiency), factor XIII deficiency, and mild von Willebrand disease 9. When clinical suspicion is strong despite normal screening tests, specific testing for these conditions is warranted.