Abstract
Vaso-occlusive crisis (VOC) is a significant cause of morbidity and mortality in sickle cell anemia (SCA) patients; however, its mechanisms are poorly understood. In view of their prothrombotic nature, we hypothesized that SCA-associated VOC may be due to the presence of anti-annexin V antibodies. Anti-annexin V antibodies were measured with ELISA in 177 VOC and 81 steady-state SCA patients. Anti-annexin V IgM and IgG concentrations were significantly higher in VOC patients than in steady-state patients and were associated with elevated VOC risk. After categorizing anti-annexin V antibodies, the adjusted odds ratio increased as the percentile value increased. Monovariate logistic regression analysis demonstrated a positive dose-effect relationship for anti-annexin V IgM with VOC, with increased VOC risk seen with increased antibody titers. Multivariate logistic regression analyses confirmed the association of anti-annexin V IgM, more so than IgG, as an independent VOC risk factor. Anti-annexin V IgG antibodies correlated positively with VOC type and negatively with HbF and age of VOC onset, while anti-annexin V IgM correlated positively with VOC type, duration, frequency, site, pain severity, hospitalization, and medication, and negatively with age of VOC onset and HbS levels. High levels of anti-annexin V IgM antibodies constitute a risk factor for VOC in SCA patients.