Association of RBC adhesion to ICAM-1 with select clinical phenotype in HbSS SCD. Subjects with a history of intracardiac or intrapulmonary shunt have significantly higher RBC adhesion compared with those with no history of shunt. A history of nephropathy or ACS does not have a significant association with RBC adhesion levels. The P value was calculated using a 2-sample Student t test. ns, not significant.