However, many studies were limited by small sample size [15,16,22,23] and a lack of a population-based comparison cohort [11–13,15,16,19,21–23]. AIDS-related opportunistic infections, neoplasms and HIV infection per se have been hypothesized to predispose patients to a hypercoagulable state [16]. Various other abnormalities in the haemostatic pathways of HIV-infected

patients have also been reported [25–27]. An association between HIV-induced immunodeficiency and low Acalabrutinib ic50 levels of several thrombophiliac components, for example, protein S, protein C and antithrombin III, as well as high levels of anticardiolipin antibodies, has been proposed [16,25,27,28]. Although VTE risk may be related to HIV-induced immunodeficiency [16,17], no studies to date have determined the impact of HIV, low CD4 cell count and HAART on the risk of VTE in HIV-infected patients on a nationwide scale. We conducted a

population-based nationwide cohort study to examine the risk of VTE in HIV-infected patients compared with a general population comparison cohort. We also examined the impact of low CD4 cell count and HAART on the risk of VTE in HIV-infected patients, as well as the risk posed by injecting drug use (IDU). As of 1 January 2007, Denmark had a population of 5.5 million [29], with an estimated HIV prevalence of 0.07% among adults [30]. Medical care, Pritelivir in vitro including antiretroviral treatment, is tax-supported and provided free of charge to all HIV-infected residents of Denmark. Treatment of HIV infection is restricted to eight specialized medical centres, where patients are seen on an out-patient basis at intended intervals

of 12 weeks. During the Megestrol Acetate follow-up period of our study, national criteria for initiating HAART were HIV-related disease, acute HIV infection, pregnancy, CD4 cell count<300 cells/μL, and, until 2001, plasma HIV RNA>100 000 HIV-1 RNA copies/mL. The DHCS, which has been described in detail elsewhere, is a nationwide, prospective, population-based cohort study of all Danish HIV-infected patients treated at Danish hospitals since 1 January 1995 [30,31]. The data are updated on a yearly basis and include demographics, route of infection, all CD4 cell counts, viral loads and antiretroviral treatment. The DCRS, established in 1968, stores information on vital status, residency, and immigration/emigration for all Danish residents [32]. A 10-digit personal number [Central Personal Registry (CPR) number], assigned at birth, uniquely identifies each citizen. The DNHR, established in 1977, records all hospital diagnoses according to the International Classification of Diseases [8th revision (ICD-8) until the end of 1993 and 10th revision (ICD-10) thereafter], all operations according to NCSP (NOMESCO Classification of Surgical Procedures – the Danish edition) and, since 1995, all hospital out-patient visits. ICD-9 has never been used in Denmark [33].