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Validation of a de novo Paediatric Warfarin Nomogram

1The Royal Children's Hospital, Department of Clinical Haematology, Parkville, Australia, 2University of Melbourne, Department of Nursing, Calton, Australia, 3Murdoch Children's Research Institute, Parkville, Australia, 4University of Melbourne, Calton, Australia

Abstract Number: PB0798

Meeting: ISTH 2021 Congress

Theme: Pediatrics » Thrombosis in Neonates and Children

Background: Warfarin therapy in children is impacted by many variables, including diet and concurrent illness. To support the implementation of a self-management program within a paediatric anticoagulation service, a paediatric-specific warfarin nomogram was needed. A literature review revealed no published paediatric nomograms therefore a de novo nomogram was developed drawing upon the hospital’s warfarin management evidence-based guideline.

Aims: This study aimed to validate a paediatric warfarin nomogram.

Methods: A retrospective audit of electronic medical records compared the dosing and international normalised ratio (INR) retest decisions made by haematology clinicians to the dosing and retesting recommended by a de novo warfarin nomogram at a tertiary pediatric hospital. Children (aged six months-18 years) on warfarin therapy for longer than six months were included. Data was collected between September 2019 and February 2020.  Descriptive data analysis was performed and the study was approved by the hospital human research ethics committee.

Results: Warfarin dosing and INR retest decisions made by haematology clinicians for 25 children were included, equating to 396 INR tests. The nomogram matched 79.3% of clinicians dosing decisions and 23.5% of INR retest decisions. 53% of the recommended retest dates were earlier than the nomogram’s recommendation. In the INR 2.0-3.0 group, 62.5% of INR results were within the TTR and 83.0% of dosing decisions matched the nomogram. In the INR 3.0-4.0 group, only 43.5% of INR results were within the target range and the nomogram matched 65.9% of dosing decisions.

Conclusions: These preliminary results suggest this de novo paediatric nomogram is reliable and valid tool for warfarin dosing, as recommended warfarin doses matched the majority of clinicians’ dosing decisions. Dosing decisions and INR retesting recommendations from the nomogram most accurately matched haematology team decisions when the INR was in range. Further analysis is needed confirm the validity of the nomogram in children with unstable INRs.

To cite this abstract in AMA style:

Jones S, Monagle P, Allan A, Chen S, Dawson K, Kuzmitsky A, Pham-Crepps M, Renner-Hahn E, Greenway A, Newall F. Validation of a de novo Paediatric Warfarin Nomogram [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/validation-of-a-de-novo-paediatric-warfarin-nomogram/. Accessed June 25, 2022.

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