[1] Univ Washington, Dept Pharm, Seattle, WA 98195 USA
[2] Hop St Antoine, F-75571 Paris, France
[3] Univ Washington, Dept Epidemiol, Seattle, WA 98195 USA
[4] Childrens Mem Hosp, Dept Radiol, Chicago, IL 60614 USA
[5] Univ Colorado, Hlth Sci Ctr, Dept Pediat, Denver, CO 80262 USA
[6] Childrens Hosp, Denver, CO 80218 USA
[7] Colorado Dept Hlth, Dis Control & Environm Epidemiol Div, Denver, CO 80220 USA