Academic journal article Bulletin of the World Health Organization

The Development of a MUAC-for-Height Reference, Including a Comparison to Other Nutritional Status Screening Indicators

Academic journal article Bulletin of the World Health Organization

The Development of a MUAC-for-Height Reference, Including a Comparison to Other Nutritional Status Screening Indicators

Article excerpt

Introduction

Mid-upper-arm circumference (MUAC) has been used for many years as an alternative index of nutritional status of children in situations, such as famines or refugee crises, where the collection of height and weight measurements is difficult (1-4). Also MUAC has been used as an additional screening tool in nonemergency situations because of its power to predict childhood mortality (5-7).

A single MUAC cut-off value (generally 12.5 cm or 130.0cm), which is based on observations on normal, well-fed Polish children in the early 1960s (1, 8, 9), has been used over the last 30 years for children under 5 years of age. However, the idea that MUAC is age- and sex-independent in young children has recently been questioned, and it has been suggested that MUAC Z-scores, which adjust for differences by age and sex, are a more useful indicator of nutritional status (10, 11). A WHO Expert Committee has recommended a new MUAC-for-age reference for children aged 6-60 months (12, 13).

In order to facilitate field work to assess nutritional status rapidly, a method was developed in the 1960s to relate the measured MUAC to the child's height using a special measuring stick -- the QUAC stick (Quaker Arm Circumference measuring stick) (14, 15). The QUAC stick method, which measures the arm circumference at the mid-upper level and compares this value with the child's height, is simple, inexpensive, easy to use, independent of correct age, and fairly reliable (16-21). However, the QUAC stick reference data that are currently being used are derived from separate sets of MUAC data based on well-nourished Polish children (9) and from height data based on healthy West Nigerian village children (14, 18) or on country-specific data (19). In this article we provide a MUAC-for-height reference for international use based on the same set of data recommended by a WHO Expert Committee for use as a MUAC-for-age reference (12,13). We also propose a "standard" QUAC stick, which facilitates comparison of data between countries.

Methods

To develop the MUAC-for-height growth reference, we used the growth data for children aged 6 months to [is less than) 10 years from the sample collected for the first and second National Health and Nutrition Examination Surveys for the USA (NHANES I, NHANES II) (22, 23). These two surveys were conducted by the National Center for Health Statistics (NCHS) to provide data for representative samples of the civilian non-institutionalized population in the USA. NHANES I examined persons aged 1-74 years over the period 1971 74, and NHANES 11 those aged 6 months to 74 years over the period 1976-80. Detailed descriptions of the samples selected have been published elsewhere (22, 23). There were a total of 23 808 MUAC measurements front a combined NHANES I and NHANES II sample of children aged 6 months to less than 10 years.

To estimate the median MUAC values over a small range of heights, we used the exploratory data analysis (EDA) line-fitting method ("three-group resistant line") (24). The data were divided into three subgroups based on height, the median MUAC calculated for each subgroup, and a line fitted through these three summary medians. We used 6-cm wide height windows and subdivided these into 2-cm wide subgroups: for example, the MUAC data for 77.0 82.9cm were divided into the subgroups 77.0-78.9cm, 79.0-80.9cm, and 81.0-82.9cm and the median MUAC was calculated for each subgroup. A line was then fitted through the medians and the predicted MUAC determined at 80.0cm (the midpoint of the height windows) (see Fig. 1). This procedure was repeated for every 6-cm window of height, with midpoints ranging from 65.0 to 145.0cm calculated at 1.0-cm intervals (i.c. a total of 81 times). A smoothed median curve was then fitted through the 81 predicted medians using a 5th degree polynomial.

[Figure 1 ILLUSTRATION OMITTED]

Using the smoothed median curve, we calculated the residuals of each data point and the standard deviation (SD) for each 6-cm window about the smoothed median curve. …

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