Age-independent anthropometry: an examination of data from rural Khartoum, Sudan

The data collected in a mixed cross-sectional longitudinal survey of children in a village in rural Khartoum, Sudan, were analysed in order to identify age-independent anthropometric indices. The mean values of weight/height, weight/height, mid arm circumference, mid arm fat area and triceps skinfold thickness all change little with age over certain parts of the age range. 15% of the boys and 22% of the girls had weights less than 75% of standard weight for age. The ability of age-independent indices to identify these low-weight individuals was investigated in terms of their sensitivity and specificity. Weight/height discriminated best, correctly classifying 85% of the low weight boys and 78% of the normal weight boys in the under-five age group. Weight/height and mid arm circumference were also useful, but triceps skinfold thickness and mid arm fat area did not discriminate usefully. All tests performed better in the under-five age group than in the older age bands.