Lu Ban1, Alyshah Abdul Sultan2, Joe West3, Laila J Tata4, Richard D Riley5, Catherine Nelson-Piercy6, Matthew J Grainge7. 1. NIHR Nottingham Biomedical Research Centre (BRC), Nottingham University Hospitals NHS Trust and the University of Nottingham, C-floor, South Block, Queen's Medical Centre, Derby Road, Nottingham NG72UH, UK; Nottingham Digestive Diseases Biomedical Research Centre, School of Medicine, University of Nottingham, E-floor, West Block, Queen's Medical Centre, Derby Road, Nottingham NG72UH, UK. 2. Centre for Prognosis, School of Primary, Community and Social Care, Keele University, David Weatherall Building, Keele, Staffordshire ST5 5BG, UK. Electronic address: alyshah.abdulsultan@astrazeneca.com. 3. NIHR Nottingham Biomedical Research Centre (BRC), Nottingham University Hospitals NHS Trust and the University of Nottingham, C-floor, South Block, Queen's Medical Centre, Derby Road, Nottingham NG72UH, UK; Population and Lifespan Sciences, School of Medicine, University of Nottingham, Clinical Sciences Building Phase 2, City Hospital, Nottingham NG5 1PB, UK. Electronic address: joe.west@nottingham.ac.uk. 4. Population and Lifespan Sciences, School of Medicine, University of Nottingham, Clinical Sciences Building Phase 2, City Hospital, Nottingham NG5 1PB, UK. Electronic address: laila.tata@nottingham.ac.uk. 5. Centre for Prognosis, School of Primary, Community and Social Care, Keele University, David Weatherall Building, Keele, Staffordshire ST5 5BG, UK. Electronic address: r.riley@keele.ac.uk. 6. Women's Health Academic Centre, Guy's and St Thomas' NHS Foundation Trust, St Thomas Hospital, Westminster Bridge Rd, London SE1 7EH, UK. Electronic address: Catherine.Nelson-Piercy@gstt.nhs.uk. 7. Population and Lifespan Sciences, School of Medicine, University of Nottingham, Clinical Sciences Building Phase 2, City Hospital, Nottingham NG5 1PB, UK. Electronic address: matthew.grainge@nottingham.ac.uk.
Abstract
INTRODUCTION: Venous thromboembolism (VTE) is the leading cause of direct maternal mortality in high-income countries. We previously developed a risk prediction score for postpartum venous thromboembolism (VTE) in women without a previous VTE. In this paper, we provide further external validation and assess its performance across various groups of postpartum women from England. MATERIALS AND METHODS: Cohort study using primary and secondary care data covering England. We used data from QResearch comprising women with pregnancies ending in live birth or stillbirth recoded in Hospital Episodes Statistics between 2004 and 2015. Outcome was VTE in the 6 weeks postpartum. Our predictor variables included sociodemographic and lifestyle characteristics, pre-existing comorbidities, and pregnancy and delivery characteristics. RESULTS: Among 535,583 women with 700,185 deliveries, 549 VTE events were recorded (absolute risk of 7.8 VTE events per 10,000 deliveries). When we compared predicted probabilities of VTE for each woman from the original model with actual VTE events, we obtained a C-statistic of 0.67 (95% CI 0.65 to 0.70). However, our model slightly over-predicted VTE risk for the higher risk women (calibration slope = 0.84; 95% CI 0.74 to 0.94). Performance was similar across groups defined by calendar time, socioeconomic status, age group and geographical area. The score performed comparably with the existing algorithm used by the UK Royal College of Obstetrician and Gynaecologists. CONCLUSIONS: Our model enables flexibility in setting new treatment thresholds. Adopting it in clinical practice may help optimise use of low-molecular-weight heparin postpartum to maximise health gain by better targeting of high-risk groups.
INTRODUCTION: Venous thromboembolism (VTE) is the leading cause of direct maternal mortality in high-income countries. We previously developed a risk prediction score for postpartum venous thromboembolism (VTE) in women without a previous VTE. In this paper, we provide further external validation and assess its performance across various groups of postpartum women from England. MATERIALS AND METHODS: Cohort study using primary and secondary care data covering England. We used data from QResearch comprising women with pregnancies ending in live birth or stillbirth recoded in Hospital Episodes Statistics between 2004 and 2015. Outcome was VTE in the 6 weeks postpartum. Our predictor variables included sociodemographic and lifestyle characteristics, pre-existing comorbidities, and pregnancy and delivery characteristics. RESULTS: Among 535,583 women with 700,185 deliveries, 549 VTE events were recorded (absolute risk of 7.8 VTE events per 10,000 deliveries). When we compared predicted probabilities of VTE for each woman from the original model with actual VTE events, we obtained a C-statistic of 0.67 (95% CI 0.65 to 0.70). However, our model slightly over-predicted VTE risk for the higher risk women (calibration slope = 0.84; 95% CI 0.74 to 0.94). Performance was similar across groups defined by calendar time, socioeconomic status, age group and geographical area. The score performed comparably with the existing algorithm used by the UK Royal College of Obstetrician and Gynaecologists. CONCLUSIONS: Our model enables flexibility in setting new treatment thresholds. Adopting it in clinical practice may help optimise use of low-molecular-weight heparin postpartum to maximise health gain by better targeting of high-risk groups.