From the Guidelines
To avoid false negative results in clotting factor assays and fibrin degradation product assays after transfusion, wait at least 90–120 min after the infusion ends, and consider taking a level 6 hours after the infusion ends for more accurate results. This recommendation is based on the British Thoracic Society guidelines for the management of non-tuberculous mycobacterial pulmonary disease (NTM-PD) 1.
Key Considerations
- The timing of sample collection is crucial to avoid false negatives, as transfused blood products can temporarily alter the patient's coagulation profile.
- Taking a level 90–120 min after the infusion ends can provide a more accurate measure of the peak level, while taking a level 6 hours after the infusion ends can help to extrapolate back to time=0 and use this as the peak level 1.
- Alternatively, taking a level of 60 min after infusion ends may be appropriate as a measure of the peak level, but may underestimate the true peak level 1.
Clinical Implications
- The waiting period is necessary because transfused blood products, such as fresh frozen plasma and cryoprecipitate, contain exogenous clotting factors and other hemostatic components that can mask underlying coagulation defects or consumption processes.
- In emergency situations where testing cannot be delayed, it is essential to note the timing of sample collection relative to transfusion on the laboratory requisition to aid in proper interpretation.
- Proper collection technique, including the use of citrated tubes (light blue top) for coagulation studies, is also crucial to avoid hemodilution or activation.
From the Research
Wait Time for Clotting Factor Assay and Fibrin Degradation Product Assay Post Transfusion
- The optimal wait time for clotting factor assay and fibrin degradation product assay post transfusion to avoid false negatives is not directly addressed in the provided studies 2, 3, 4, 5, 6.
- However, the studies suggest that the timing of these assays can be crucial in accurately diagnosing coagulopathy and fibrinolysis-related conditions.
- For example, a study on the diagnostic possibilities of specific fibrin(ogen) degradation products in relation to venous thromboembolism found that the values of the area under the curve of the receiver operating characteristic curve for fibrinogen elastase degradation product and fibrin degradation product assays were lower than D-dimer 3.
- Another study on the use of tranexamic acid in severely injured patients found that patients with depletion of fibrinolysis inhibitors had significantly increased D-dimer levels and lower fibrinogen levels, and that tranexamic acid improved fibrin clot strength in patients with hyperfibrinolysis 4.
- A study on functional fibrinogen assay found that fibrinogen is critical in correcting abnormal clot strength following trauma, and that a TEG-based functional fibrinogen assay can assess the contribution of fibrinogen and platelets to clot strength 5.
- A review of D-dimer assays found that D-dimer is very sensitive to intravascular thrombus and may be markedly elevated in disseminated intravascular coagulation, acute aortic dissection, and pulmonary embolus, but that elevations can also occur in normal pregnancy, active malignancy, and with age 6.
Assay Timing Considerations
- The timing of clotting factor assay and fibrin degradation product assay post transfusion may depend on various factors, including the type of transfusion, the patient's underlying condition, and the specific assay being used 2, 3, 4, 5, 6.
- Further research is needed to determine the optimal wait time for these assays to avoid false negatives and ensure accurate diagnosis and treatment of coagulopathy and fibrinolysis-related conditions.