[1] Univ Colorado, Dept Neurol, Denver, CO 80202 USA
[2] Univ Calif San Francisco, Dept Neurol, 505 Parnassus Ave,Box 0114, San Francisco, CA 94143 USA
[3] San Francisco Gen Hosp & Trauma Ctr, Clin Lab, San Francisco, CA 94110 USA
[4] Univ Calif San Francisco, Dept Lab Med, San Francisco, CA 94143 USA