HIV Infection As A Risk Factor For Venous Thrombosis A Case-Control Study At Kenyatta National Hospital

Abstract

Background: The association between HIV infection and venous thrombosis has long been postulated. It is estimated that HIV infected patients have a 2 to 10 fold increased risk of developing venous thrombosis. However the majority of studies done were retrospective cohort with selection bias and no controls. All the studies were undertaken in first world countries with missing confounding variables. A systematic review by Klein et al of these major studies concluded that there is some evidence linking HIV infection with venous thrombosis but further studies preferably case-control are needed to elucidate this link. Venous thrombosis remains a common cause of morbidity and mortality in both ambulatory and hospitalized patients. Objective: To establish if there is an association between venous thrombosis and HIV infection amongst patients at Kenyatta National Hospital Study Design, Site and Subjects This was a hospital based case control study at Kenyatta National Hospital. Admitted patients with clinical and doppler evidence of deep venous thrombosis and/or patients with pulmonary embolism confirmed with Computed Tomography Pulmonary Angiogram were defined as a case. Controls were age and sex matched individuals without clinical evidence of deep venous thrombosis and/or pulmonary embolism who seek voluntary HIV testing at the Voluntary Counselling and Testing center in Kenyatta National Hospital within the study period. A case to control ratio of 1:1 was used. Clinical Method: Consecutive sampling method of both cases and controls was done. A consent form was issued to the participant for signing after counselling about the study. The data collecting form was filled with the help of the Principal Investigator or research assistant to obtain relevant data for the study controlling for venous thrombosis risk factors. The participant was examined by the principal investigator and pertinent variables such as BMI, HIV status, smoking history, cancer, recent central venous catheterization, recent surgery trauma or immobilization, pregnancy, use of oral contraceptive pills and long distance travelling was noted. Patient confidentiality was maintained throughout this research. xi Data Analysis: The results are presented in the form of tables and charts using SPSS version 21. The association between venous thrombosis and HIV was done using univariate analysis and odds ratio. Multivariate logistic regression analysis was done to determine factors independently associated with venous thrombosis. Results: Of the 62 cases of venous thrombosis 23 were HIV positive. Of the 62 controls only 7 were positive for HIV. In a univariate analysis the odds of having venous thrombosis in an HIV positive patient was 4.634 times than that of HIV negative patients (P=0.001, 95% CI 1.810 – 11.866). Controlling for traditional risk factors in a multiple logistic regression model, HIV remained an independent risk for venous thrombosis with an aOR 6.6 (P=0.006, 95% CI 1.7 – 25.6). Conclusion: HIV is a risk factor for venous thromboembolism. The odds of venous thrombosis in an HIV infected person is 5 to 7 times higher than the general population