PB1190 - Evaluation of Anti-Xa assay for monitoring Low Molecular Weight Heparin (LMWH) using dedicated Stago reagent and analyser

Background: Low molecular weight heparins (LMWH) are a class of anticoagulants used in patients for the prevention and treatment of venous and arterial thromboembolism. The availability of an in-house anti-Xa assay against LMWH is useful for monitoring the effect of LMWH in certain clinical situations. In Khoo Teck Puat Hospital, Anti-Xa LMWH test is currently referred to a reference laboratory. Each month, the Department of Laboratory Medicine receives an average of seven Anti-Xa LMWH test requests.

Aims: The authors sought to evaluate the performance of an Anti-Xa LMWH assay suitable for implementation in-house

Methods: Twenty-one previously-assayed citrated plasma samples provided by our current referral laboratory were used for the evaluation. Split-sample analysis was performed on the 21 samples: in-house using the STA®-Liquid anti-Xa LMWH on Stago STA Compact Max instrument (Diagnostica Stago, France) and in KK Women’s and Children’s Hospital (KKH) laboratory using the same instrument-reagent combination as reference. The results were compared using Two-Instrument Comparison module of the EP Evaluator statistical software.

Results: The trueness study showed a slope of 0.889 and intercept of 0.026. The R2 value is 0.9819. The QCs performed during the evaluation period showed a imprecision of 3.0% and 3.8% for normal and abnormal controls which is within manufacturer’s specification. A slight negative bias was observed but sample deterioration cannot be excluded. Overall, there was no significant difference observed between the in-house assay and the reference laboratory.

Conclusion(s): The evaluated Anti-Xa LMWH reagent and instrument demonstrated comparable performance against the reference laboratory. The Stago instrument-reagent combination can be integrated into a General Laboratory workflow with relative ease, making it a good option for laboratories that need accommodate increasing number of patients who require monitoring for LMWH.