Interobserver reliability of skinfold measurements in infants and young children

Anthropometric measurement error and the assessment of nutritional status

Anthropometry involves the external measurement of morphological traits of human beings. It has a widespread and important place in nutritional assessment, and while the literature on anthropometric measurement and its interpretation is enormous, the extent to which measurement error can influence both measurement and interpretation of nutritional status is little considered. In this article, different types of anthropometric measurement error are reviewed, ways of estimating measurement error are critically evaluated, guidelines for acceptable error presented, and ways in which measures of error can be used to improve the interpretation of anthropometric nutritional status discussed. Possible errors are of two sorts; those that are associated with: (1) repeated measures giving the same value (unreliability, imprecision, undependability); and (2) measurements departing from true values (inaccuracy, bias). Imprecision is due largely to observer error, and is the most commonly used measure of anthropometric measurement error. This can be estimated by carrying out repeated anthropometric measures on the same subjects and calculating one or more of the following: technical error of measurement (TEM); percentage TEM, coefficient of reliability (R), and intraclass correlation coefficient. The first three of these measures are mathematically interrelated. Targets for training in anthropometry are at present far from perfect, and further work is needed in developing appropriate protocols for nutritional anthropometry training. Acceptable levels of measurement error are difficult to ascertain because TEM is age dependent, and the value is also related to the anthropometric characteristics of the group of population under investigation. R > 0.95 should be sought where possible, and reference values of maximum acceptable TEM at set levels of R using published data from the combined National Health and Nutrition Examination Surveys I and II (Frisancho, 1990) are given. There is a clear hierarchy in the precision of different nutritional anthropometric measures, with weight and height being most precise. Waist and hip circumference show strong between-observer differences, and should, where possible, be carried out by one observer. Skinfolds can be associated with such large measurement error that interpretation is problematic. Ways are described in which measurement error can be used to assess the probability that differences in anthropometric measures across time within individuals are due to factors other than imprecision. Anthropometry is an important tool for nutritional assessment, and the techniques reported here should allow increased precision of measurement, and improved interpretation of anthropometric data.

Facial measurements in clinical genetics: How important are the instruments we use?

Prompted by our finding that a popular compendium of clinical measurements often suggests a transparent ruler as a suitable substitute for anthropometric calipers (which were typically used by the original researchers to collect the normative data), we compared facial measurements taken with a ruler and calipers. Our objectives were to compare facial measurement data taken with these instruments by two classes of observer: expert and inexperienced. Ten facial measurements were repeated on four medically normal women by one expert and one inexperienced observer. Both observers' data showed that the caliper-derived means were usually the larger, but, whereas the expert observer's caliper-derived data typically were the least variable, the novice observer had smaller standard deviations and ranges for the ruler-derived data. Statistically significant differences were found between the ruler- and caliper-derived data from both observers on all four subjects, except for subnasale-pogonion and stomion-pogonion. For the novice observer only, endocanthion-endocanthion, left exocanthion-endocanthion, and alare-alare were also nonsignificant. The calibrations of the sliding caliper and ruler were compared to determine if differences between them could explain the statistical results, but were the same. We concluded that the differences between the caliper- and ruler-derived measurements resulted because the ruler often could not be placed directly on the landmarks, as could the arms of the calipers. We recommend that clinicians interested in taking facial measurements to assess their patients consult the original publications for information on the techniques and instruments used so that reliable comparisons with the normative data can be made.

Growth and fitness of Canadian inuit: Secular trends, 1970-1990

The growth and development of Inuit children and adolescents living in the high arctic (Igloolik, NWT, 69°40' N, 81°W) has been surveyed crosssectionally and semilongitudinally on three occasions during a period of rapid acculturation: 1969-1970, 1979-1980, 1989-1990. Recruitment declined from 85% (1969-1970) to 63% (1989-1990) of eligible subjects, in the most recent survey a total of 91 males and 65 females. Secular trends in the community have included a change from nomadic to settled life, improved access to health care, reduction of average family size, a progressive shift from country to market foods, the introduction of a 12-grade school, and a progressive reduction of habitual physical activity with the advent of television and video programs. The stature of the youngest students has tended to increase by ∼1cm/decade, possibly as a consequence of dietary changes and resultant earlier maturation, but the stature of older adolescents has tended to decrease, possibly as a consequence of spinal trauma sustained during high-speed snowmobile operation. In the boys, the estimated onset of rapid pubertal growth has advanced from an age of 13-14 to 12-13 years, and in the girls, the period of rapid growth is now already established at 11 years. Over the 20 years of observation, skinfold thicknesses at any given age have increased, handgrip and knee extension forces have diminished, and relative aerobic power has also decreased. In consequence, the current generation of Inuit children are no more fit than their sedentary peers in southern Canada. © 1994 Wiley-Liss, Inc.

Intra- and interobserver concordance in classifying dental morphology

A sample of 50 Kodiak Island Eskimo dental casts were observed, using standard reference plaques, three times by one observer and once by a second observer, for 47 graded and discrete morphological characters of the dentition and jaws. Although the frequency of both intra- and interobserver scoring differences between observation sessions are relatively high for some characters, statistical analysis reveals that differences are largely random in direction and cancel out. Most dental morphological variants can be observed in a ranked fashion with adequate within- and between-observer reliability. However, four traits present both within- and between-observer difficulties: the tuberculum dentale, the canine distal accessory ridge, marginal accessory cusps of the upper first premolar, and the anterior fovea on the lower first molar.