Effective October 10, 2025, Corewell Health Reference Laboratory West will implement an updated protocol for the Lupus Screen (LAB478). This change is designed to improve diagnostic accuracy for patients undergoing anticoagulant therapy, where false-positive or false-negative results can complicate clinical decision-making.
Recent studies have demonstrated that anticoagulants, particularly direct Xa inhibitors, can significantly affect Lupus testing outcomes. To mitigate this, our laboratory is implementing best practices as outlined in the following sources:
- Favaloro EJ, Res Pract Thromb Haemost. 2024;8(3):102385
- Favaloro EJ, Res Pract Thromb Haemost. 2022;6(2):e12676
- Dr. Goodwin’s article in CAP Today, “D-dimer reporting, INR among the variables that matter” August 2025
These sources emphasize the importance of screening for anticoagulants prior to Lupus testing to avoid misleading results.
What’s Changing?
Before performing the Lupus Screen, the lab will now run a UFH anti-Xa assay to detect anticoagulant presence. Based on the results:
- If the UFH anti-Xa < 0.10 IU/mL
→ Lupus Screen will be performed similar to current process. - If the UFH anti-Xa > 1.0 IU/mL
→ It will be reported with the following comment:
“Testing indicates the presence of a direct Xa inhibitor or other novel anticoagulant that may lead to a false negative or positive test result. Repeat testing once the patient is free of anticoagulant therapy is recommended if clinically indicated”
→ Lupus Screen test will be cancelled. - If the UFH anti-Xa results between 0.10 and 1.0 IU/mL
→ An aPTT Heparin Neutralization assay (Epic Test ID: LAB3377) will be performed:- If heparin is neutralized → Lupus Screen proceeds
- If heparin is not neutralized → Lupus Screen test is canceled with the same comment as above.
This protocol ensures that Lupus testing is only performed when results are likely to be reliable, reducing the risk of misdiagnosis due to anticoagulant interference. Providers are encouraged to consider timing of anticoagulant therapy when ordering Lupus testing.
Questions?
For any questions or concerns, please contact the hematopathologist covering coagulation services, or the on-call hematopathologist after hours.