|Assessment of Nutritional Status in Emergency-Affected Populations - Adolescents (UNSSCN, 2000, 24 p.)|
|Which anthropometric index?|
MUAC is relatively simple and easy to measure and has recently been recommended for use in rapid screening of adults for undernutrition to determine the need for admission to a feeding programme19, 59, 64, 65. In many well-nourished populations, a reasonable correlation exists between MUAC and BMI in adults. A scheme using a combination of MUAC and BMI has been proposed to categorise the degree of undernutrition in adults 65. No MUAC cut-offs have been established for the diagnosis of adolescent undernutrition yet. The published results of several nutrition assessment surveys of adolescents in developing countries include MUAC data; however, because of the lack of a reference population and cut-off points, no estimate of the prevalence of undernutrition could be made 4, 7, 51, 53, 66-71.
Lack of data directly correlating measurements to measurements of body fat and protein stores - there are no data directly correlating MUAC with other measures of body fat and undernutrition, such as BMI, in adolescents. In addition, there are no data relating MUAC cut-off points with functional or health outcomes in adolescents. Hence, as yet there are no validated cut-off points to define undernutrition with MUAC measurements in adolescents.
Age - MUAC changes substantially with age during adolescence, as shown in several reference populations from industrialised countries 41, 72. As a result, a different cut-off point must be used for adolescents of different ages. This requires an accurate age for each survey subject in order to judge whether they fall above or below an age-specific cut-off point.
Sexual development - MUAC changes with sexual development. The rapid addition of soft tissue, predominantly muscle tissue in males and subcutaneous fat in females, which occurs with puberty results in a more rapid rise in MUAC at this time than prior to or following puberty. One study clearly demonstrates a greater MUAC in postmenarcheal female adolescents than premenarcheal female adolescents of the same age 53.
Ethnicity - ethnic differences in MUAC have not been sufficiently studied to determine if a single cut-off point for MUAC could be used for adolescents in all ethnic groups.
Measurement error - in spite of the convenience and ease of measurement, MUAC measurement requires careful training and supervision in order to prevent wrapping the measuring tape too tightly or too loosely, which results in an erroneous estimate. One study estimated that the smallest change over time detectable in MUAC was 8-10%, when measurements were taken by different observers73. A second study demonstrated that MUAC measurements show more inter-observer variability than weight and height measurements 74.
MUAC should be measured at the mid-point of the upper arm between the shoulder (lateral end of the clavicle) and elbow (inferior tip of the olecranon). Although this not critical in young children who often have little muscle contour in the upper arm, it becomes increasingly important in post-pubertal adolescents who have developed adult musculature. Therefore workers will have to be carefully trained to measure adolescent MUACs.