Purpose:
To compare the effect of hemoglobin and hematocrit levels on the severity of sickle cell retinopathy (SSR).
Methods:
Retrospective study of patients with SSR. Data was collected between January 2005 to January 2010. Collected data included patient demographics, sickle cell genotype (SS/SC/Other), hemoglobin (Hgb) and hematrocrit (Hct) levels, and severity of retinopathy based on the Goldberg staging criteria at initial presentation. Patients with SSR were divided into two groups based on their severity of retinopathy: Group A included patients with retinopathy of stage 3 or above (neovascularization) and Group B included patients with less than stage 3 retinopathy. Patients were excluded from this study if they had any other retinopathy due to other causes. All data was analyzed using STATA 11 software.
Results:
Seventy nine patients were included in this study (40 males, 39 females). Mean age was 33 years. 30 patients were found to have Hgb SC, 36 patients with Hgb SS, and 13 with other Hbg genotypes. 40 patients met the staging requirements for Group A and had 39 patients were included in Group B. The average Hgb level in Group A was 10.95 gm/dl and in Group B was 9.14 gm/dl (p=0.0002). The average Hct level in Group A was 31.45% and in Group B was 26.07% (p<0.0001). Subgroup analysis comparing the two major Hbg genotypes showed the average Hbg level in Hgb SS patients was 8.97 gm/dl and in Hgb SC patients was 11.56 gm/dl (p<0.0001).
Conclusions:
A significant difference was found between the two group’s hemoglobin and hematocrit levels. We found that the group with less severe retinopathy (less than stage 3 retinopathy) has lower Hgb and Hct levels and the group with more severe retinopathy has higher Hgb and Hct levels which was statistically significant. This study shows that low Hbg and Hct levels may have a protective effect on the progression of sickle cell retinopathy. Perhaps higher Hgb and Hct levels may be associated with increased blood viscosity in sickle cell patients causing occlusion of peripheral capillaries which may exacerbate retinopathy. Further, larger powered multi-centered studies will be needed to further elucidate these findings.
Keywords: retinal neovascularization • retina • hypoxia