Anticardiolipin antibodies: a study of frequency in TIA and stroke. We undertook a prospective study of consecutive patients to determine the frequency of elevated IgG and IgM anticardiolipin antibodies in transient ischemic attack and ischemic stroke and found elevated IgG antibodies in 8.2% (9 of 110) and IgM in 9.1% (10 of 110), only the former being significantly greater than in a healthy control population. We suggest that anticardiolipin screening be concentrated on the young. 