Dear Dr Santa Rosa: My team published an articule about this issues among Ecuadorian population. You can find it in the Bulletin of Panamerican Health Organization 28(2), 1994. Let me know if you need more help. Sincerely, Ricardo Izurieta, MD, MPH University of Alabama at Birmingham e-mail: XFAC017 at UABDPO.DPO.UAB.EDU