Background: The risk of venous thromboembolism (VTE) is increased in women who use combined oral contraceptives (COC). Therefore, a risk assessment model identifying women at low/high risk before starting COC would be clinically valuable in guiding the choice of whether or not to prescribe COC.
Aims: The aim of this study was to develop and externally validate a risk assessment model for VTE in women within one year of starting COC.
Methods: Data from the MEGA study, a large population-based case-control study was used. Candidate predictor were chosen based on literature. Multiple imputation was used for missing data, with five imputed datasets and pooling according to Rubin’s rules. Using logistic regression, a backward selection procedure was performed to obtain the most optimal model (clinical+genetic and clinical only model). The discriminative value of the models was assessed by calculating the area under the curve (AUC) of the ROC curve.
Results: 179 Cases and 577 controls were included within 1 year after starting COC. Tables 1 and 2 show preliminary results regarding the AUC values for each model.
The clinical model contained predictors which are not (commonly) used in the clinic, e.g., injury, co-morbidity, but also expected variables, e.g., family history of VT.
The clinical+genetic model had a higher AUC value: 0.813 (95%CI: 0.776-0.851) than the clinical only model: 0.771 (95%CI: 0.729-0.812).
Conclusions: Current results show that adding genetic risk factors improved the performance of the clinical model and may suggest that screening for genetic variants may be important in women starting COC. Future steps will be to explore other methods of variable selection, i.e., Lasso, to perform internal and external validation of the models, and to develop a scoring system based on regression coefficients to simplify the model and to make its usage optimal in the clinic.
| Full | Clinical+Genetic | Clinical | |
| Age Plastercast | x x | x | x |
| Hospital admission Surgery | x x | x | x |
| Bedridden Injury | x x | x x | x x |
| Inflammation Varicosis | x x | ||
| Comorbidity Tromboflebitis | x x | x | x x |
| Family history of VTE Body mass index | x x | x x | x x |
| Smoking Factor V Leiden | x x | x | |
| Prothrombin | x | x | |
| Non-O bloodtype | x | x |
[Candidate predictors in each model.]
| AUC | 95% CI | |
| Full | 0.814 | 0.776 – 0.852 |
| Clinical+Genetic | 0.813 | 0.776 – 0.851 |
| Clinical | 0.771 | 0.729 – 0.812 |
[AUC values of each model]
To cite this abstract in AMA style:
Khialani DK, Arcudi S, Cannegieter S, van Hylckama Vlieg A. Development and External Validation of a Risk Assessment Model for First Venous Thromboembolism in Women Starting Combined Oral Contraceptives [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/development-and-external-validation-of-a-risk-assessment-model-for-first-venous-thromboembolism-in-women-starting-combined-oral-contraceptives/. Accessed March 3, 2021.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/development-and-external-validation-of-a-risk-assessment-model-for-first-venous-thromboembolism-in-women-starting-combined-oral-contraceptives/