Prevalence of Relative Systemic Hypertension in Ghanaian Adults with Sickle Cell Disease

Introduction: Sickle cell disease (SCD) is associated with an increased risk of premature death in adults. Relative systemic hypertension (RSH) is associated with increased risk of vascular disorders in SCD. While drugs targeting RSH may halt the development of sickle vascular disorders, the magnitude of this problem is unknown in many countries, including in Ghana, which has ~2% incidence rate of SCD. In this study, we examined the prevalence of relative hypertension in an adult SCD patient population of the Ghana Institute of Clinical Genetics (GICG), Korle-Bu, Accra, Ghana and described their demographic characteristics, genotypes and complications.

Methods: With institutional ethics committee approval, we conducted a retrospective chart review of 1000 adults aged ≥ 18 years with SCD receiving regular care at the GICG. Charts were selected as patients visited the clinic for routine care over a ten month period. SCD patients 18 years or older who had 3 blood pressure (BP) measurements on separate clinic visits for at least one year were eligible for the study. RSH was defined as systolic BP (SBP) 120 mmHg to 139 mmHg and diastolic blood pressure (DBP) 70 mmHg to 89 mmHg on at least two consecutive routine visits or visits for mild illness. We collected data on demographics, genotypes, the three most recent consecutive BPs, blood counts done on days the BPs were recorded and documented complications of SCD. A data extraction manual was used to reduce inter-observer variability. Descriptive statistics were used for data analysis. The prevalence of relative systemic hypertension in the group was calculated.

Results: There were 873 eligible cases involving 319 males (36.5%) and 554 females (63.5%). Homozygous SCD (SS) and Heterozygosity for sickle cell and hemoglobin D disease accounted for 56.9% of cases, Hb SC 39% and other genotypes (e.g. S-Beta Thalassemia, Hb SF) 4%. The overall prevalence of RSH was 40.4%; Hb SS 35.8% and Hb SC 47.7%. Among the 353 patients with RSH, 145 (41.1%) were male, and 208 (58.9%) were female. The predominant genotypes in the RSH group were SS (50.4%) and SC 46.2%. Other genotypes accounted for 3.4%. Median systolic BP (SBP) for the entire cohort was 116.6 (range 86.6 - 171.1) mmHg, and the median diastolic BP (DBP) was 70.3 (range 48 to 113.6) mmHg. Median blood pressures were higher in patients with Hb SC (males: 123/75, females: 122/76 mmHg) than those with Hb SS (males: 117.6/67, females 111/67mmHg). Complications were noted as follows; avascular necrosis (6.9%), other bone disease (1.1%) leg ulcers (6.3%), cholelithiasis (3.7%), cardiopulmonary 1%, and renal 1%. Pearson correlation coefficient showed associations between blood pressure, age, hemoglobin (Hb), and WBC. There was a positive correlation between SBP and age (r = 0.088, p = 0.009) and total Hb (r = 0.106, p = 0.002). Spearson's correlation revealed significant positive correlation between SBP and leg ulcers (r = 0.074, p ≤ 0.05); DBP and leg ulcers (r = 0.119, p ≤0.01); DBP and priapism (r = 0.075, p =0.026) and DBP and cholelithiasis (r = 0 .086, p=0.011).

Conclusions: There is a 40.4% prevalence of RSH, which to the best of our knowledge represents the first estimate of this condition in the Ghanaian adult SCD population. The prevalence among Hb SS patients is 35.8% compared to the 44% previously reported in the US. There is significant positive correlation of BP with Hb, leg ulcers, priapism and cholelithiasis. Future prospective studies using standardized BP monitoring are warranted to validate preemptive treatment of RSH in SCD.