Norman W. Staehling

Rapid nutrition surveys : how many clusters are enough ?

On the basis of theoretical considerations, population-based nutrition surveys of 30 clusters of 30 children should provide reasonably valid estimates of the prevalence of malnutrition with at least 95 per cent confidence that the estimated prevalence differs from the true value by no more than 5 per cent. In areas of famine in Africa, where an urgent need often exists for rapid nutritional assessment to determine the extent and severity of the problem, visiting 30 sites is often logistically difficult. To determine the effects of using fewer than 30 clusters on the validity and precision of the estimated level of undernutrition, we used data from the 1983 Swaziland National Nutrition Survey and from rapid nutrition surveys performed in 1984 and 1985 in Burkina Faso, Guinea, and Niger. Fewer than 30 clusters may result in point prevalence estimates that differ dramatically from the true prevalence and, in most instances, are less precise. In contrast, little is gained by collecting more than 30 clusters. In summary, around 30 clusters provides relatively valid and precise estimates of the prevalence of undernutrition, and every effort should be made to obtain the logistic support required to study this number of clusters.

Arm Circumference v. Weight-for-Height in Nutritional Assessment: Are the Findings Comparable?

Arm circumference has been proposed as an alternative to weight-for-height as a measure of acute malnutrition because of its low cost and ease of performance particularly for rapid field assessments of nutritional status in circumstances where resources and trained personnel are limited. Few studies however have compared the 2 methods as a measure of acute malnutrition. We used data from rapid nutrition assessments conducted during 1984-85 in Burkina Faso Guinea and Niger to compare the prevalence of malnutrition as measured by these 2 indices employing commonly used cut-offs for severe and moderate malnutrition. The prevalence of severe malnutrition was 5% using the cut-off of arm circumference 12.5 cm and and 1% using the cut-off of weight-for-height 70% of median; for moderate malnutrition (arm circumference 13.5 cm and weight-for-height 80% of median) the corresponding prevalences were 20 and 8%. For severe malnutrition the sensitivity of arm circumference compared with weight-for-height was 54% with a specificity of 95%. For moderate malnutrition sensitivity and specificity were 75 and 85% respectively. Raising the arm circumference cut-offs used to define severe and moderate malnutrition resulted in higher sensitivity but yielded lower specificity. Our results indicate that considerable different prevalence rates were obtained with the 2 measures at the cut-offs used and that despite substantial overlap arm circumference and weight-for-height identify somewhat different children as malnourished. Further work needs to focus on functional outcomes such as morbidity and mortality comparing children with low arm circumference to those with low weight-for-height to better evaluate the relative usefulness of the 2 measuring techniques in identifying children at nutritional risk. (authors modified)

SAHEL NUTRITION SURVEYS, 1974 and 1975

The Sahel region of.West-Central Africa consists of an area approximately 300 miles wide extending from 13 to 20 degrees north latitude, and including parts of Mali, Mauritania, Upper Volta, Niger and Chad. The total population of these countries is approximately 20 million in an area of 2 million square miles. Shipments of food and relief supplies to the Sahel began in 1973 following several years of inadequate rainfall. The need for a scientific evaluation of the impact of the drought on the nutritional status of the population was recognised, and the United States Agency for International Development (USAID) asked the Centre for Disease Control (CDC) of the US . Public Health Service to undertake such an evaluation. After methodological problems were worked out in 1973, the first formal survey of nutritional status took place in May, June and July of 1974. In order to measure changes since 1974, two surveys were conducted in 1975, the first after the annual harvest, and the second immediately before the rainy season, approximately one year after the 1974 survey. The results of these three surveys are the subject of this paper. The objective of the surveys was to quantify the extent of acute proteinenergy malnutrition in the rural population of that part of each country estimated to be most affected by