Validity of clinic-based nutritional surveillance for prevalence estimation of undernutrition.

Few studies have been performed to assess the validity of clinic-based nutritional surveillance systems. We compared estimates of the prevalence of underweight (low weight-for-age) obtained from the clinic-based Swaziland surveillance system with estimates obtained from the 1983 National Nutrition Status Survey of Rural Swaziland. The age-adjusted prevalence of underweight among first-time clinic attenders (10.0%) was very similar to that estimated by the national survey (9.4%). However, the prevalence of underweight among children attending two or more times in a year was less than half that of first attenders (4.4%). The regional differences in the prevalence of underweight found in the national survey were not detected by the surveillance system. Surveillance data are useful in describing the nutritional status of children from clinics within the surveillance system. However, surveillance data, particularly from re-attenders, will not necessarily provide a valid estimate of nutritional status within the general population or of differences between regions.