BIOLOGICAL MARKERS OF PROTEIN-ENERGY MALNUTRITION

The biological markers of undernutrition fall into three categories: ( a) those that measure structure; (b) those that measure function; and (c) indices of the above two. Ideally a marker of nutritional status s hould have the following characteristics: specific to nutritional stat us; sensitive to changes in nutritional status; reproducible; simple t o measure; inexpensive and widely available. Unfortunately there are n o such markers, and therefore individuals involved in the assessment o f nutritional status should be aware of the advantages and disadvantag es of the markers they use. For example, body composition can be asses sed using sophisticated techniques that make fewer assumptions than si mple bedside techniques (1). However, these sophisticated techniques ( eg neutron activation, and combinations of techniques such as hydroden sitometry, water dilution techniques and dual-energy X-ray absorptiome try) are not widely available and some of them are labour intensive. O n the other hand simple bedside techniques, such as those based on ski nfold thicknesses can be applied widely because they are easy and quic k to perform, but they are probably not as accurate as the classic bod y composition techniques (hydrodensitometry or water dilution techniqu es) or other sophisticated methods based on the assessment of multiple body compartments (1). Therefore the choice of method depends not onl y on the availability of investigative tools, but also on the practica lities of using them in individuals, a small group of individuals, or large groups of individuals, (eg national surveys during famine and no n-famine conditions). In this brief review only some aspects concerned with simple bedside or laboratory methods will be discussed.