[1] Stanford Univ, Sch Med, Dept Pediat, Suite 100,770 Welch Rd, Palo Alto, CA 94301 USA
[2] San Francisco Unified Sch Dist, Sch Hlth Programs Dept, San Francisco, CA 94116 USA
[3] Univ Calif San Francisco, Dept Pediat, San Francisco, CA 94143 USA
[4] Univ N Carolina, Cecil G Sheps Ctr Hlth Serv Res, Chapel Hill, NC 27599 USA