Incidence of a first venous thrombotic event in people with HIV in the Netherlands: a retrospective cohort study

Background The risk of venous thrombotic events is elevated in people with HIV, but overall risk estimates and estimates specific to immune status and antiretroviral medication remain i mprecise. In this study, we aimed to estimate these parameters in a large cohort of people with HIV in the Netherlands. Methods In this retrospective cohort study, we used the Dutch ATHENA cohort to estimate crude, age and sex standardised, and risk period-specific incidences of a first venous thrombotic event in people with HIV aged 18 years or older attending 12 HIV treatment centres in the Netherlands. Crude and standardised incidences were compared with European population-level studies of venous thrombotic events. We used time-updated Cox regression to estimate the risk of a first venous thrombotic event in association with HIV-specific factors (CD4 cell count, viral load, recent opportunistic infections, antiretroviral medication use) adjusted for traditional risk factors for venous thrombotic events. Findings With data collected from Jan 1, 2003, to April 1, 2015, our study cohort included 14 389 people with HIV and 99 762 person-years of follow-up, with a median follow-up of 7.2 years (IQR 3.3-11.1). During this period, 232 first venous thrombotic events occurred, yielding a crude incidence of 2.33 events per 1000 person-years (95% CI 2.04-2.64) and an incidence standardised for age and sex of 2.50 events per 1000 (2.18-2.82). CD4 counts less than 200 cells per mu L were independently associated with higher risk of a venous thrombotic event: adjusted hazard ratio (aHR) 3.40 (95% CI 2.28-5.08) relative to counts of 500 cells per mu L. A high viral load (aHR 3.15, 95% CI 2.00-5.02; >100 000 copies per mL vs <50 copies per mL) and current or recent opportunistic adverse events (2.80, 1.77-4.44) were also independently associated with higher risk of a venous thrombotic event. There were no associations between any specific antiretroviral drugs and risk of a venous thrombotic event. Rates associated with pregnancy (9.4, 95% CI 4.6-17.3), malignancy (16.7,10.6-25.1), and hospitalisation (24.4, 19.1-30.6) were lower than primary thromboprophylaxis thresholds suggested by the respective guidelines. Interpretation Our findings support neither prescribing primary outpatient thromboprophylaxis nor avoiding any type of antiretroviral medication in people with HIV at high risk of a venous thrombotic event.