1. National Institutes of Health, Philippine National Ear Institute, University of the Philippines, Manila, Philippines
2. University of the Philippines-Philippine General Hospital, Manila, Philippines
3. College of Medicine, Department of Otolaryngology-Head and Neck Surgery, University of the Philippines, Manila, Philippines
4. National Institutes of Health, Institute of Clinical Epidemiology, University of the Philippines, Manila, Philippines
5. College of Medicine, Department of Clinical Epidemiology, University of the Philippines, Manila, Philippines