Cluster 541: complying capable understanding protocol signed document informed consent requirements subject Cluster 1148: provide ability informed consent willingness english follow patient adhere assessments Cluster 1604: comply ability willingness protocol study requirements procedures follow consent informed Cluster 1915: length entire comply designee procedures understand study enrolling ability determined Cluster 2164: mental compromise comply impairment ability requirements informed consent study deficits Cluster 2391: voluntary written consent informed donor research related aspects procedures comply