Bulletin of the World Health Organization

Using lot quality-assurance sampling and area sampling to identify priority areas for trachoma control: Viet Nam

Mark Myatt, Nguyen Phuong Mai, Nguyen Quang Quynh, Nguyen Huy Nga, Ha Huy Tai, Nguyen Hung Long, Tran Hung Minh, and Hans Limburg



To report on the use of lot quality-assurance sampling (LQAS) surveys undertaken within an area-sampling framework to identify priority areas for intervention with trachoma control activities in Viet Nam.


The LQAS survey method for the rapid assessment of the prevalence of active trachoma was adapted for use in Viet Nam with the aim of classifying individual communes by the prevalence of active trachoma among children in primary school. School-based sampling was used; school sites to be sampled were selected using an area-sampling approach. A total of 719 communes in 41 districts in 18 provinces were surveyed.


Survey staff found the LQAS survey method both simple and rapid to use after initial problems with area-sampling methods were identified and remedied. The method yielded a finer spatial resolution of prevalence than had been previously achieved in Viet Nam using semiquantitative rapid assessment surveys and multistage cluster-sampled surveys.


When used with area-sampling techniques, the LQAS survey method has the potential to form the basis of survey instruments that can be used to efficiently target resources for interventions against active trachoma. With additional work, such methods could provide a generally applicable tool for effective programme planning and for the certification of the elimination of trachoma as a blinding disease.