New Reference Data for MUAC for Height Measurements

A published paper

MUAC measurements have traditionally been used in emergency situations as a rapid means of assessing population levels of wasting and screening for selective feeding programmes when the collection of height and weight measurements are difficult. Over the years a single MUAC cut-off point (generally 12.5 cm or 13cm) has been used to identify malnourished children under five. These cut-off points were based on data sets from normal, well fed Polish children in the 1960s. However, there has been a lot of controversy over the years as to whether MUAC is age and sex-independent in the under fives and therefore whether it is appropriate to have single cut-off point based on a combined MUAC for boys and girls or whether a MUAC for age indicator should be used instead.

A WHO Expert Committee has recently recommended a new MUAC-for Age set of reference data for children aged 6-60 months (Bulletin of World Health Organisation 1997, Vol. 75, 4). It is nevertheless widely acknowledged that any nutritional indices which involve the collection of age data can be problematic, especially in emergency settings, as age data may be imprecisely given by parents.

During the 1960s a method was developed to relate the measured MUAC to the child's height using a special measuring stick - the QUAC stick (Quaker Arm Circumference measuring stick). The method was independent of correct age, inexpensive, easy to use and fairly reliable. It became the main anthropometric assessment tool of a few agencies. e.g. ICRC. However, most agencies stuck with weight for height measurements when conducting nutritional surveys as measurements involving MUAC were believed to be prone to greater inaccuracies for a number of reasons, e.g. difficulties in identifying the mid point of the arm, the arm may be kept too flaccid, or the tape may be pulled too tightly or not tightly enough. A recent article has provided a MUAC for height reference data suitable for international use based on the same set of data recommended by the WHO expert Committee for use as a MUAC for age reference (a representative sample of children aged 659 months in the USA). The previous QUAC stick reference data were derived from separate sets of MUAC data based on well-nourished Polish children and from height data based on healthy West Nigerian village children or on country-specific data. The article also proposes use of a standard QUAC stick, which facilitates comparison of data between countries. The authors of the article show that MUAC for height Z scores (and MUAC for age Z scores) are better predictors of weight for height than MUAC measurements based on a fixed cut-off point of 12.5 or 13 cms. The authors point out that MUAC for height measurements have certain advantages over weight for height measurements in emergency or refugee situations; first they do not require the use of cumbersome scales and second they are less influenced by errors in measuring height. In other words an inaccuracy in height measurement will have a far greater influence on the final Z score for weight for height than it would in MUAC for height measurements. Height measurements are likely to be problematic where a completely flat platform with a vertical wall behind cannot be found. However, the authors recognise that in most situations it is more likely that the MUAC measurement will be inaccurate. They therefore conclude that the QUAC stick technique should only be used as a rapid method for determining levels of nutrition in large populations and as a screening tool for malnourished children.

A WHO modified QUAC stick is described in the annex to the article including details of its construction and use. The reference data in the article are meant to be used with the modified QUAC stick.

The full paper can be found in Bullet in of the World Health Organisation, 1997, vol. 7S, (4) pp333-341