Annex 2 - Recommended measurement protocols and derivation of indices

1. Introduction

The manner in which anthropometric and related data are collected requires careful attention. Correct procedures for obtaining the basic measurements are central to the appropriate use and interpretation of anthropometry. The use of specified protocols accomplishes several objectives: it ensures that measurements are comparable with reference data, facilitates interpretation of results, provides a basis for training and standardization of data collectors, and maximizes the reliability of measurements.

This annex provides the basic information necessary for collecting measurements recommended for use in the various age and physical status groups. Specific techniques and details of applications and interpretation of the measurements are provided within the main sections of the report. More complete discussions of anthropometric protocols for many of the recommended measurements and for measurements that may be used for other purposes may be found elsewhere (1, 2). To be consistent with the recommended reference data, arm circumference and skinfolds should be measured on the right side of the body.

Training data collectors is important for the proper use of anthropometry, and various publications provide procedures for standardization - ensuring that all observers take measurements in the same way (3, 4). It is also important that training curricula cover issues of sensitivity to local customs, dress, and practices of modesty, especially where proper measurement will require the exposure of certain parts of the body. Many problems in this area may be avoided by using observers of the same sex as the subjects.

For almost all age groups, it is recommended that age, sex, height, and weight are recorded; other measurements may be restricted to a single group (e.g. fundal height in pregnancy, attainment of adult voice in adolescence). Table A2.1 may be used to identify all measurements recommended for a particular age or status group or to identify the group or groups in which a specific measurement is advocated.

2. Determination of age and sex

2.1 Chronological age

Since many of the recommended measurements and reference data are considered in terms of chronological age, accurate age determination is important, especially for very young children and during adolescence because of the rapid rates of growth. In many areas, birth date is formally registered, and chronological age can be obtained through interviews and verified from records, if necessary. Where birth dates are not commonly known or recorded, efforts should be made to approximate age as accurately as possible; some approaches based on local cultural designations or calendar-related events have been successful in this regard (5). Except in emergency situations, however, children’s age should not be approximated according to height or weight: small children are likely to be considered younger than they are, and prevalence of undernutrition will therefore be underestimated.

Table A 2.1
Measurements recommended for use in particular age and status groups

		Age or status group
Measurement		Pregnancy	Newborn	Infancy	Childhood	Adolescence	Adult, overweight	Adult, thinness	Elderly
	Age	X	X	X	X	X	X	X	X
	Sex	X	X	X	X	X	X	X	X
	Gestational age	X	X
	Symphysis-fundus height	X
	Height	X			X	X	X	X	X
	Sitting height							X	X
	Length		X	X	X
	Weight	X	X	X	X	X	X	X	X
Circumferences
	Head		X	X
	Arm	X			X			X	X
	Chest		X
	Abdomen						X		X
	Hip						X		X
	Calf	X							X
Skinfold thicknesses
	Triceps					X		X	X
	Subscapular	X				X			X
	Thigh	X
Maturational indicators
	Menarcheal status					X
	Breast stage 2 (B2)					X
	Genital stage 3 (G3)					X
	Adult voice (AV)					X
Derived indices
	Weight loss							X	X
	Body mass index	X				X	X	X	X
	Ponderal index		X
	Abdomen:hip ratio						X		X
	Arm muscle circumference							X
	Arm muscle area							X

Counting the number of deciduous teeth in young children may be appropriate for assigning them to age groups, but is an unsatisfactory method for individuals because of the wide variation in the timing of deciduous eruption (6). Eruption of permanent teeth in adolescents is more sensitive to environmental influences than that of deciduous teeth in younger children; counting the number of permanent teeth in adolescents will result in underestimation of chronological age in populations whose overall somatic maturation has been delayed by environmental factors (7). Moreover, variation in the timing of permanent tooth eruption makes this an inappropriate method of estimating chronological age of the individual. Assessment of the recommended maturational indicators will allow grouping of adolescents into general categories that may be useful for interpreting anthropometric data, but is not appropriate for estimating chronological age in individuals.

2.2 Gestational age

For newborns, gestational age should be assessed, and may be considered as the number of completed weeks since the first day of the last normal menstrual period (LMP). The LMP date is obtained by interviewing the mother carefully. Alternatively, when ultrasound equipment is available, early (< 20 weeks) ultrasonic measurements of fetal dimensions can improve the estimate of gestational age (8).

2.3 Sex

Because of the systematic differences in anthropometric dimensions at most ages, recommended reference data are reported separately for males and females. The collected data should therefore include the sex of individuals concerned. Distinctions between sexes will usually be obvious, although parents or other family members may need to be consulted in the case of small children.

3. Measurement protocols

3.1 Height, sitting height, length, and weight

Height (adapted from reference 2)

The measurement of height requires a vertical board with an attached metric rule and a horizontal headboard that can be brought into contact with the uppermost point on the head. The individual to be measured should be barefoot or in thin socks and wearing little clothing so that the positioning of the body can be seen. He or she should stand on a flat surface, with weight distributed evenly on both feet, heels together, and the head positioned so that the line of vision is perpendicular to the body. The arms hang freely by the sides, and the head, back, buttocks, and heels are in contact with the vertical board. Anyone who cannot stand straight in this position should be positioned vertically so that only the buttocks and the heels or the head are in contact with the vertical board. The individual is asked to inhale deeply and maintain a fully erect position. The movable headboard is brought onto the topmost point on the head with sufficient pressure to compress the hair. For consistency with methods used to collect the recommended reference data, no additional upward pressure is exerted on the mastoid processes. The height is recorded to the nearest 0.1 cm.

Two measurers are needed to determine the height of children aged 2-3 years. One measurer places a hand on the child’s feet to prevent lifting of the heels and to keep the heels against the vertical board, and makes sure the knees are extended with the other hand. The second lowers the headboard and observes the height reading.

Note: See section 9.4.2 for height measurements in the elderly.

Sitting height (adapted from reference 2)

The measurement of sitting height requires a table and an anthropometer or measuring stick with a horizontal headboard. The individual sits on the table with the legs hanging unsupported over the edge and with the hands resting on the thighs. The posture is as erect as possible, and the line of vision parallel to the ground. It is useful for the measurer to apply gentle pressure with the right hand over the lumbar area and the left hand, simultaneously, on the superior part of the sternum; this reinforces the erect position. Gentle upward pressure on the mastoid processes ensures the fully erect seated posture.

The anthropometer is positioned vertically in the midline behind the subject so that it nearly touches the back. The measurer’s left hand is placed under the subject’s chin to assist in holding the proper position, and the right hand moves the blade of the anthropometer onto the vertex (the topmost point of the head). The subject is instructed to take a deep breath, and the measurement is made just before he or she exhales and recorded to the nearest 0.1 cm.

Length (adapted from reference 2)

Two observers are required to measure recumbent length. The subject lies in a supine position on a recumbent length table or measuring board. The crown of the head touches the stationary, vertical headboard. The subject’s head is held with the line of vision aligned perpendicular to the plane of the measuring surface. The shoulders and buttocks are flat against the table top, with the shoulders and hips aligned at right angles to the long axis of the body. The legs are extended at the hips and knees and lie flat against the table top, and the arms rest against the sides of the trunk. The measurer ensures that the legs remain flat on the table and shifts the movable board against the heels. In infants, care is taken to extend the legs gently. The length is recorded to the nearest 0.1 cm.

Weight (adapted from reference 2)

During infancy, a levelled pan scale with a beam and movable weights is preferred. Other types of scales may be used where pan scales are unavailable; all types should be regularly calibrated. Birth weight should be determined within 12 hours of birth. The infant, with or without a diaper, is placed on the scales so that the weight is distributed equally about the centre of the pan. When the infant is lying or suspended quietly (which may require patience), weight is recorded to the nearest 10 g. When an infant is restless, it is possible to weigh the mother while she is holding the infant and again without the infant, but this procedure is unreliable, partly because the mother’s weight will usually be recorded to the nearest 100 g. If a diaper is worn, its weight is subtracted from the observed weight: reference data for infants are based on nude weights.

An individual who is able to stand without support is weighed using a levelled platform scale with a beam and movable weights. He or she stands still in centre of the platform, with the body weight evenly distributed between both feet. Light indoor clothing can be worn, but shoes, long trousers, and sweaters should be removed. The weight of the remaining clothing is not subtracted from the observed weight when the recommended reference data are used; however, if heavy clothing must be worn during weighing because of cultural constraints, adjustments should be made before weight measurements are interpreted. Weight is recorded to the nearest 100 g.

Individuals, other than infants, who cannot stand unsupported by reason of disability can be weighed using a beam chair scale or bed scale. If an adult weighs more than the upper limit on the beam, a compensating weight can be suspended from the left-hand end of the beam and the measurer must then determine how much weight must be placed on the platform for the scale to record zero. When the subject is reweighed, this compensatory weight is added to his or her measured weight.

Note: See section 9.4.1 for weight measurements in the elderly.

3.2 Circumferences

Measurements of body circumferences require a flexible but inelastic (non-stretchable) graduated tape measure.

Head circumference (adapted from reference 2)

Head circumference is measured with the infant held or seated on the lap of the mother or care-taker. Objects such as hairpins are removed from the hair. The tape is positioned just above the eyebrows and placed posteriorly to give the maximum circumference. It is pulled sufficiently tight to compress hair and yield a measure that “approximates” cranial circumference. The measurement is recorded to the nearest 0.1 cm.

Mid-upper arm circumference (adapted from reference 2)

For measurement of MUAC the subject stands erect, with the arms hanging freely at the sides of the trunk, the palms towards the thighs. Loose clothing without sleeves is worn to allow total exposure of the arm and shoulder area. The circumference is measured at the midpoint of the arm. To locate the midpoint, the subject’s elbow is flexed to 90° with the palm facing upward. The measurer locates the lateral tip of the acromion at the shoulder, and a small mark is made at the identified point. The most distal point on the olecranon process of the ulna (at the point of the elbow) is located and marked. A measuring tape placed over these two marks is used to find the midpoint between them, which is marked.

With the subject’s arm relaxed, the elbow extended and hanging just away from the side of the trunk, and the palm towards the thigh, the tape is placed around the arm and positioned perpendicular to the long axis of the arm at the marked midpoint. With the tape snug to the skin but not compressing soft tissues, the circumference is recorded to the nearest 0.1 cm.

Note: See section 9.4.5 for measurements in the elderly.

Chest circumference (adapted from reference 2)

An infant is measured when held or seated on the lap of the mother or care-taker; the chest should be bare. The arms are abducted slightly to permit passage of the tape around the chest. When the tape is snugly in place, the arms are lowered to their natural position at the sides of the trunk. Chest circumference is measured at the level of the fourth costosternal (rib) joints, counting the number of ribs from above. The measurement is made in a horizontal plane to the nearest 0.1 cm at the end of a normal expiration.

Abdominal circumference (adapted from references 2 and 9)

The subject stands comfortably with his or her weight evenly distributed on both feet, and the feet about 25-30 cm apart. The measurement is taken midway between the inferior margin of the last rib and the crest of the ilium, in a horizontal plane. Each landmark should be palpated and marked, and the midpoint determined with a tape measure and marked. The observer sits by the side of the subject and fits the tape snugly but not so tightly as to compress underlying soft tissues. The circumference is measured to the nearest 0.1 cm at the end of normal expiration.

Hip (buttocks) circumference (adapted from reference 2)

Wearing only nonrestrictive briefs or underwear, or a light smock over underwear, the subject stands erect with arms at the sides and feet together. The measurer sits at the side of the subject so that the level of maximum extension of the buttocks can be seen, and places the tape measure around the buttocks in a horizontal plane. An assistant may be needed to help position the tape on the opposite side of the subject’s body. The tape is snug against the skin but does not compress the soft tissues. The measurement is recorded to the nearest 0.1 cm.

Calf circumference (adapted from reference 2)

The subject sits on a table so that the leg to be measured hangs freely; alternatively, he or she stands with the feet about 20 cm apart and weight distributed equally on both feet. The tape measure is positioned horizontally around the calf and moved up and down to locate the maximum circumference in a plane perpendicular to the long axis of the calf. The tape is in contact with the skin over the whole circumference but does not indent the skin. The measurement is recorded to the nearest 0.1 cm. During infancy and in the elderly, calf circumference can be measured with the subject supine and the knee flexed to 90°.

Note: See section 9.4.3 for further details of measurements in the elderly.

3.3 Skinfold thicknesses

Skinfolds should be measured using skinfold callipers, such as Lange or Holtain callipers, that provide standardized pressure at all jaw openings. Some plastic models are available and may be preferred for non-research purposes. General guidelines for measuring skinfolds should be consulted for those inexperienced in these methods (1, 2).

Triceps skinfold (adapted from reference 2)

The triceps skinfold is measured in the midline of the posterior aspect of the arm, over the triceps muscle, at a level midway between the lateral projection of the acromion process at the shoulder and the olecranon process of the ulna (at the point of the elbow). With the elbow flexed to 90°, the midpoint is determined by measuring the distance between the two landmarks using a tape measure; it is marked on the lateral side of the arm. Except for infants and the handicapped, the subject should be measured standing, with the arm hanging loosely and comfortably at the side. The calliper is held in the measurer’s right hand. A vertical fold of skin and subcutaneous tissue is picked up gently with the left thumb and index finger, approximately 1 cm proximal to the marked level, and the tips of the callipers are applied perpendicular to the skinfold at the marked level. Measurements are recorded to the nearest 0.5 mm (Lange callipers), 0.2 mm (Holtain callipers), or smallest unit of graduation.

Note: See section 9.4.6 for measurements in the elderly.

Subscapular skinfold (adapted from reference 2)

The subscapular skinfold is picked up gently on a diagonal, inclined infero-laterally at approximately 45° to the horizontal plane in the natural cleavage lines of the skin. The site is just inferior to the inferior angle of the scapula. The subject stands comfortably erect, with the arms relaxed at the sides of the body. To locate the site, the measurer palpates the scapula, running the fingers inferiorly and laterally along its vertebral border until the inferior angle is identified. For some subjects, especially the obese, gently placing the arm behind the back will help identify the site. The calliper jaws are applied 1 cm infero-lateral to the thumb and finger raising the fold, and the thickness is recorded to the nearest 0.5 mm (Lange callipers), 0.2 mm (Holtain callipers), or smallest unit of graduation.

Note: See section 9.4.4 for measurements in the elderly.

Thigh skinfold (anterior) (adapted from reference 2)

The thigh skinfold site is located in the midline of the anterior aspect of the thigh, midway between the inguinal crease and the proximal border of the knee cap (patella). The subject flexes the hip to assist location of the inguinal crease. The thickness of the vertical fold is measured while the subject stands. The body weight is shifted to the other foot while the leg on the measurement side is relaxed with the knee slightly flexed and the foot flat on the floor. The calliper jaws are applied about 1 cm distal to the fingers holding the fold, and the thickness of the fold is recorded to the nearest 0.5 mm (Lange callipers), 0.2 mm (Holtain callipers), or the smallest unit of graduation.

3.4 Maturational indicators in adolescence

More complete descriptions and discussions of stages of secondary sexual characteristics used as maturational indicators may be found elsewhere (10, 11).

Menarcheal status (girls) (adapted from reference 12)

Menarcheal status is determined by interview. At the time of questioning each subject is asked her age (or her date of birth) and whether she has begun to menstruate. A knowledge of local language and terminology for referring to menstruation is necessary so that the information obtained is correct.

B2 - Breast development (girls) (adapted from references 10 and 11)

Breast stage 2 (B2) is an arbitrary stage in the process of areolar and breast development in adolescence. It is the breast bud stage, characterized by elevation of the breast and papilla as a small mound, in contrast to the lack of palpable breast tissue in childhood; areolar diameter is enlarged and areolar tissue is elevated.

G3 - Genital development (boys) (adapted from references 10 and 11)

Genital stage 3 (G3) is an arbitrary stage in the process of development in size and shape of penis and scrotum in adolescence. It is characterized by enlargement of the penis, especially in length, compared with the childhood form; enlargement of testes and descent of the scrotum are also evident.

Voice change (boys) (adapted from reference 13)

The recommended maturational indicator is the attainment of the adult voice (sometimes designated AV). It is important to specify that for the recommended uses, the voice change noted is not the so-called “breaking” or husky adolescent voice, but the attainment of the adult voice. The pitch and resonance of the voice has adult characteristics. It may be helpful for assessment to have boys read or recite a chosen text.

3.5 Other measurements

Fundal height (symphysis-fundus height) (adapted from reference 14)

A measuring tape of nonelastic material is required. The distance between the upper border of the symphysis pubis to the superior fundus uteri is recorded to the nearest 0.1 cm.

4. Derived indices

The following seven recommended indices are derived from the basic measurements:

· Percentage weight loss, or weight change, is calculated as:

Weight must be measured in the same units on all occasions.

· Sitting height: height ratio is expressed as a decimal fraction:

· Body mass index (BMI) is calculated as:

Body mass index may be calculated directly from observed measurements of weight and height, determined from a nomogram (Fig. A2.1), or derived from Table A2.2.

· Ponderal index (Rohrer’s) (PI) for newborn is calculated as:

Figure A 2.1 - Nomogram for obtaining body mass index from height, H (cm), and weight, W (kg)^a

Directions

1. Locate the person’s height on the left column. Numbers in this column increase going down the scale.

2. Locate the person’s weight on the right column. Numbers in this column decrease going down the scale.

3. Lay a ruler or straightedge so that it touches these two points - height and weight.

4. Note where the straightedge crosses the slanted line between these two columns. This is the body mass index value.

5. Enter the body mass index value in the person’s record.

^a Adapted from reference 16 with the permission of the American Society for Clinical Nutrition.

WHO 95129

Table A 2.2 - Body mass index for selected heights and weights

Table A 2.2 (continued)

· Abdomen:hip ratio (AHR) is expressed as a decimal fraction:

· Arm muscle circumference (AMC) is estimated from arm circumference (AC) and triceps skinfold thickness (TSF), assuming a circular and concentric model (15):

AMC (cm) = AC (cm) - [p × TSF (cm)]

· Arm muscle area (AMA). Cross-sectional arm muscle area is estimated from arm circumference (AC) and triceps skinfold thickness (TSF), assuming a circular and concentric model (15)

Corrections of AMA for estimated bone areas in each sex are recommended for some purposes:

References

1. Cameron N. The measurement of human growth. London, Croom Helm, 1984.

2. Lohmann TG, Roche AF, Martorell R, eds. Anthropometric standardization reference manual. Champaign, IL, Human Kinetics Books, 1988.

3. Measuring change in nutritional status. Geneva, World Health Organization, 1983.

4. Assessing the nutritional status of young children. New York, United Nations, 1990.

5. Jelliffe DB, Jelliffe EFP. Community nutritional assessment. Oxford, Oxford University Press, 1989.

6. Delgado H et al. Nutritional status and the timing of deciduous tooth eruption. American journal of clinical nutrition, 1975, 28:216-224.

7. Hagg U, Taranger J. Dental development, dental age and tooth counts. Angle orthodontist, 1985, 55:93-107.

8. Kramer MS et al. The validity of gestational age estimation by menstrual dating in term, preterm, postterm gestations. Journal of the American Medical Association, 1988, 260:3306-3308.

9. Measuring obesity: classification and description of anthropometric data. Report on a WHO Consultation on the Epidemiology of Obesity, Warsaw, 21-23 October 1987. Copenhagen, WHO Regional Office for Europe, 1989 (unpublished document EUR/ICP/NUT 125, obtainable on request from WHO Regional Office for Europe, 8 Scherfigsvej, 2100 Copenhagen 0, Denmark).

10. Tanner JM. Growth at adolescence, 2nd ed. Oxford, Blackwell, 1962.

11. Van Wieringen JC et al. Growth diagrams 1965 Netherlands. Groningen, Wolters-Noordhoff, 1971.

12. Eveleth PB, Tanner JM. Worldwide variation in human growth, 2nd ed. Cambridge, Cambridge University Press, 1990.

13. Hagg U, Karlberg J, Taranger J. The timing of secondary sex characteristics and their relationship to the pubertal maximum of growth in boys. In: Carlson DS, ed. Orthodontics in an aging society. Ann Arbor, Ml, Center for Human Growth and Development, 1989:167-179.

14. Belizan JM et al. Diagnosis of intrauterine growth retardation by a simple clinical method: measurement of uterine height. American journal of obstetrics and gynecology, 1978, 131:643-646.

15. Heymsfield S et al. Anthropometric assessment of adult protein-energy malnutrition. In: Wright RA, Heymsfield S, eds. Nutritional assessment. Boston, Blackwell, 1984:27-82.

16. Roche AF et al. Grading body fatness from limited anthropometric data. American journal of clinical nutrition, 1981, 34: 2831 -2838.