|Appropriate Uses of Anthropometric Indices in Children - Nutrition policy discussion paper No. 7 (UNSSCN, 1990, 60 p.)|
Growth monitoring involves following changes in a child's physical development, by regular measurement of weight, and sometimes of length. It is an important tool in individual care, for early detection of health and nutrition problems in growing children (Healy et al., 1988). Deceleration in linear growth at an early age has been shown to be associated with increased risk of subsequent mortality (Van Lerberghe, 1988). Indications of growth failure alone are not readily related to specific causes, and often more information is needed to decide on the response. Growth monitoring also has the advantage of recording responses to intervention. In general, growth monitoring may provide for earlier detection of the need for intervention than one-time screening measurements (see previous section). Moreover, the trend measurement can distinguish children of adequate achieved size who are running into problems. Descriptions of growth monitoring methods are widely available - see for example the detailed reviews by Lotfi (1988), Yee & Zerfas (1987) and a special edition of the Indian Journal of Pediatrics (Vol. 55, No. 1, 1988).
Well-documented comparisons between decisions taken on the basis of growth charts and those taken on the basis of one-time measurements from screening are not readily available. The group recommended that a compilation of existing data and an assessment of the relative performance, under field conditions, of growth monitoring and one-time screening should be undertaken. An additional examination of the use of growth charts as a tool for the mobilization and application of community resources and the focusing of community decision making would be very useful.
The use of growth monitoring extends beyond problem detection. It has been used to provide a basis for communicating with mothers and with health workers, concerning child health and nutrition, and to stimulate thinking about the causes of poor growth and malnutrition. This in turn has led to action at the level of the household and of the community itself. Experience of this is, as yet, limited, but it appears very promising. Notable pioneering work has been done various settings including Colombia in the 1960's and Thailand in the 1970's and recently in the Joint WHO/UNICEF Nutrition Support Programme in Iringa, Tanzania. In the latter programme, children under 5 are weighed every 3 months, by village, and the results discussed in the village health committee. This often led, for example, to the establishment of day-care facilities. The children are classified according to weight-for-age. Those identified as malnourished are then followed up by monthly growth monitoring, often done during household visits by a village health worker.
Who to measure? Growth charts in particular have been used for healthy children, under the normal circumstances of growing up, in both developed and developing countries. It is this early and continued use which gives them a particular advantage for prevention. Thus, ideally all children should be regularly weighed and the results kept on growth charts. In practice, certainly all children enrolling in health and nutrition programmes should be issued growth charts, and mothers motivated to ensure regular weighing - preferably every month but at least every three months.
By far the commonest measurements are those of weight. Target growth rates (often called 'road to health') are generally based on the WHO/NCHS reference values - these are very similar to local references when the latter are derived from non-poor, healthy children. The point (as noted in Chapter 3) is that the chosen reference growth curves should be based on a population whose growth patterns are unconstrained by environmental factors. Concern is not with whether a child is on a given centile at one point in time, but whether its pattern of growth falls along the same centile band as age increases. This pattern provides more important information than the actual weight at any particular time. In effect, the child's longitudinal record represents its own control; the reference curves serve only to illustrate expected patterns of change.
As weight-for-age is a composite index, growth failure can be due to either a loss of weight or a failure to gain in length, or both; differentiating between these causes may be problematic. Thus, in addition to weight, measuring length would give more direct information on linear growth. If length measurements can be taken, then it would be advisable to also monitor weight-for-length.
The main difficulty in basing decisions on signals from growth charts - aside from the non-specificity to cause - is to define what growth faltering is, at different ages. Growth faltering is identified by emphasizing the direction of growth obtained in serial recordings, rather than the actual weight-for-age itself. No change or an actual decrease between successive measurements is taken as a sign of growth faltering, whereas adequate growth is reflected in a measurements tracking in parallel to the expected weight gain in the reference curve. Moreover, interpretation and action varies by the child's age. Specific interpretation of changes in weight gain varies considerably among different practitioners.14
14 One definition of growth faltering that has been used (Steveny, 1982) is as follows:
age 0-4 months: gains of < 0.5 kg per month; 6 - 15 months: three horizontal or falling monthly weights, even within the 'road to health' area (usually from -2 SD's to median); 16-60 months: three horizontal or falling monthly values, below the 'road to health' area; any loss of > 1 kg in a month; any value > 2 kg below 'road to health' area.
A practical difficulty in assessing growth rates concerns normal fluctuations in body weight over short time periods. This may be due to minor and normal changes in hydration status (including insensible loss), before/after a meal, etc. The variation thus introduced can be significant, up to several hundred grams or perhaps 50% of expected normal monthly weight change. This natural variation complicates interpretation.
In general, current practices of growth monitoring were endorsed by the meeting. Attention for future development of growth monitoring was directed towards:
- improving the definition of growth faltering and response at different ages;
- understanding and use of growth charts by health workers, and for communicating with mothers.
A. The current practices of recording weight for growth monitoring should continue.
B. Measuring length may also be useful especially when:
- resources are not constrained, so that length growth velocities can be used for additional information;
- in contrast, when coverage and regularity of weighing is poor - i.e. true monitoring is not done - weight-for-length may be assessed as a substitute.
C. Target growth rates should be based on reference values derived from populations where environmentally conditioned growth failure is minimal - the WHO/NCHS reference data meet this criterion. The child's longitudinal record serves as its own control and interest lies in the growth pattern, and whether this tracks along the same centile band as age increases.
D. A compilation and analysis of existing data should be undertaken to address the question of the advantages of growth monitoring in practice over cross-sectional screening in detection of growth faltering. This study should also determine the degree and level of significant weight loss (as distinct from normal variability) or failure to gain weight, that is of longitudinal signals with respect to diagnosis and response.