Additional clinical features identify children at risk for devel- oping elevated TCD velocities and stroke. G6PD deficiency, absence of -thalassemia (OR, 6.45; 95% CI, 2.21 18.87; P=0.001), hemoglobin levels (OR, 0.63 per 1 g/dL; 95% CI, 0.41 0.97; P=0.038), and lactate dehydrogenase levels (OR, pendent risk factors for abnormally high velocities.569 This con- and found for the first time that G6PD deficiency and hemolysis independently increased the risk of abnormal TCD.571 Another study found independent effects of hemoglobin and aspartate transaminase levels on TCD velocities, whereas age had an Several recent studies of children with SCD identified increased lactate dehydrogenase concentrations and baseline reticulocyte counts to be predictive of stroke573,574 and elevated plasma glial fibrillary acidic protein concentra- tions to be predictive of cognitive impairment, suggesting sub- Markers of systemic inflammation such as interleukin-1 also have been associated with stroke risk.576 A future process that integrates blood biomarkers and TCD blood flow findings may identify children at greatest risk. Other genetic factors also affect stroke risk in patients with SCD. A study evaluated 108 SNPs in 39 candidate genes in 1398 individuals with SCD using bayesian networks and found that 31 SNPs in 12 genes interact with fetal hemoglobin to modulate the risk of stroke.577 This network of interactions includes 3 genes in the transforming growth factor- pathway and selectin P, which is associated with stroke in the general population. 