|Assessment of Nutritional Status in Emergency-Affected Populations - Adolescents (UNSSCN, 2000, 24 p.)|
A fundamental dilemma exists in trying to measure adolescent undernutrition: a system simple enough for a non-expert is required for use in emergencies, but the reality of adolescent undernutrition is very complex. Until better tools for nutritional assessment of adolescents are developed, current recommendations regarding the use of anthropometry in adolescents must be critically examined. Their use may yield misleading results that stimulate inappropriate interventions. Given the lack of validated anthropometric procedures, anthropometric measurement of adolescents should not currently be used as the sole technique for the nutritional assessment of adolescents. Such assessments should include evaluation of the nutritional status of other population subgroups, clinical evaluation of adolescents, evaluation of food uses and access, and measurement of the levels of morbidity and mortality among adolescents and adults.
No standard method of anthropometric assessment of the nutritional status of adolescents can be recommended at this time. However, recent developments have suggested potential methods that may be used until the results of the research described above are available and a method can be recommended. The following components should be included in any anthropometric assessment of adolescents:
Screening for severe undernutrition. Until better methods can be developed and validated, screening for severe undernutrition in order to determine the need for therapeutic feeding should use clinical criteria as recommended for adults 59.
Correction for differences in age of sexual maturation. Some measure of the age of specific pubertal landmarks should be measured during nutrition surveys of adolescents. Measures that may be useful include age of menarche in females. Unfortunately, validated markers that are practical for field use do not exist for males. Correction for differences between the survey population and the reference population should be undertaken if the necessary data are available for the reference population used.
Prepubertal adolescents. Because young adolescents may be more similar to children, the most appropriate index for use in measuring undernutrition prevalence among prepubertal adolescents may be weight-for-height, at least until other indices are more fully investigated. Individuals can be compared to an existing reference using the preliminary weight-for-height tables in Annex 1. Data from this original reference population should be recalculated to provide direct weight-for-height cut-off points.
Postpubertal adolescents. Because older adolescents may be more similar to adults, BMI should be used until other indices have been more fully investigated. Nonetheless, some linear growth continues and BMI continues to change with age after attaining sexual maturity. As a result, cut-off points should be age-specific. Although several reference populations exist for which BMI centiles and/or z-scores have been calculated, the international reference population described by Cole 80 may be the best reference currently available for use in the developing world. The method for creating age-specific cut-off points described by Cole should be used to determine cut-off points, in both percent of median and z-scores, corresponding to the adult BMI cut-off points of 16, 17, and 18.5 kg m-2.
Reference populations. The reference population of American adolescents, currently recommended by WHO for use with BMI, should not be used.
Age. Both weight-for-height and BMI are age-dependent. Therefore, when these indices are used, age must be collected as accurately as possible for each survey subject or individual screened. It may be necessary to construct a local calendar to determine ages, although this may be difficult with adolescents because of the many years since birth. It may also be necessary to investigate the existence of systematically biased reporting of age which could lead to substantial under- or over- estimation of the prevalence of undernutrition when using weight-for-height or BMI.
Additional data. Adolescents should not undergo nutritional assessment in isolation. Young children, women of child-bearing age, adults, elderly, or other population subgroups should also be assessed. A large discrepancy between the estimated level of undernutrition in adolescents and other population subgroups should stimulate investigation of the validity of the methods and results of the adolescent assessment.
Comparison of surveys. In order to assess the methods and comparability of surveys, all survey reports should describe in detail the anthropometric index used, how measurements were taken, which reference population was used, how individuals were compared to this reference, the cut-off points used to define various degrees of undernutrition, and any other ancillary data collected on the population of interest.