Low Prevelance of VTE Observed Among Cohort with Sickle Cell Disease

Helen C. Okoye MBBS

A set of new findings from a cohort of patients with sickle cell disease in Nigeria suggest the prevalence of venous thromboembolism (VTE) is low among this population.

The rate of VTE was found to be 2%, which while not uncommon among sickle cell patients in Nigeria, is reported to be lower than previous reports.

“These rates, although higher in our population, were similar to the distribution in previous studies,” wrote study author Helen C. Okoye MBBS, Department of Haematology and Immunology, College of Medicine, University of Nigeria. “The implication of this would be the need for detailed thromboembolic evaluation and thromboprophylaxis in younger [sickle cell disease] patients who may be at risk of the traditional VTE risks especially in the presence of thrombotic factors.

Sickle cell disease is known to affect millions worldwide and Africa has the highest prevalence rate, with Nigeria bearing the greatest rates. Due to the high prevalence of VTE in patients with sickle cell disease in some parts of the world, there is a need to determine the accompanying rate in Nigeria.

Previous research suggested that risk factors specific to sickle cell disease contribute to a higher prevalence of thrombotic events among this patient population, relative to the general population. Thus, the current cross-sectional, retrospective study aimed to determine the VTE risk factors among patients with sickle cell disease at 4 tertiary health institutions in Nigeria.

They included patients with sickle cell disease 18 years and older receiving care at a participating facility. Investigators collected information on demographic, clinical and laboratory data, and the duration of follow-up. They additionally collected data on the use of any disease modifying agents like hydroxyurea, history and type of VTE, identifiable risk factors, and method of diagnosis.

A total of 509 sickle cell patients were included in the study and consisted of 251 (49.3%) men and 258 (50.7%) women. The mean age was 26.9 years with a median duration of follow-up at 2 years.

Of the 509 patients, data show 10 had VTE, making it a prevalence rate of 2.0%. It consisted of 9 patients who had deep vein thrombosis and 1 with pulmonary embolism. Investigators further stratified into giving a prevalence rate of 1.8% in patients less than 40 years old and 0.2% in patients ≥40 years.

No significant association was observed between VTE and age distribution (P = .898), gender (P = .752), and Hb phenotype.

They found VTE was significantly associated with acute chest syndrome (P = .002, odds ratio [OR] 8.0; 95% CI, 2.2 - 28.9], osteonecrosis (OR, 5.24; 95% CI, 1.45 - 18.91; P = .012), and vaso-occlusive crisis (P = .035).

Moreover, pulmonary hypertension (P = .001; OR, 23.3, 95% CI, 5.18 - 105.06) and stroke (P = .032; OR, 9.35; 95% CI, 0.87 - 53.25) were significantly associated with VTE.

"We recommend that prospective studies be carried out to understand the differential prevalence rates among Africans and the Western countries and to identify disease specific risks for VTE,” Okoye concluded.

The study, “Prevalence of venous thromboembolism and its associations in a large racially homogenous population of sickle cell disease patients,” was published in the European Journal of Haematology.