23 Introduction to Measurement and Assessment of Human Growth

Dr. Mary Grace Tungdim

Contents

Introduction

1.0 Growth Measurement and Assessment tools

1.1 Anthropometry

1.1.1 Measurements generally used in growth studies

1.1.1.1 Inter-observer differences

1.2 Clinical Growth Assessments

1.3 Body Composition Assessments

2.0 Methods of Studying Growth

3.0 Growth Charts

a)  Head Circumference Growth Pattern

b)  Mid Upper Arm Circumference Growth Pattern

c)  Length/ Height Growth Pattern

4.0 Why is Growth Assessment necessary?

4.1  Importance of Growth Monitoring

4.1.1 Appendix

Learning Outcomes

After this learning activity, the learner will be able to:

• Comprehend the stages of human growth
• Understand about the measurements and assessment tools used to evaluate human growth
• Understand the different methods of studying growth
• Identify the different types of growth charts
• Understand the necessity of studying growth and the plausible causes of abnormal growth

INTRODUCTION

Growth is the progressive development of a living thing, especially the process by which the various parts and organs of the body reach its point of complete physical maturity starting from fertilization by multiplication of cells and intercellular components. It is a fundamental characteristic of all living organisms. Changes in size are outcomes of three underlying cellular processes: (a) an increase in cell number or hyperplasia; (b) an increase in cell size or hypertrophy; (c) an increase in intercellular substances or accretion. Growth occupies a significant place in the study of individual diversity in form and function in man for many of these also arises through differential rates of growth of particular parts of the body relative to others.

According to Watson and Lowery (1967) “Growth means an increase in the physical size of the whole or any of its parts.” It can be measured in terms of centimeters and kilograms or metabolic balance i. e. retention of hydrogen and calcium in the body. Juan Comas defines growth as the objective manifestation of hypertrophy and hyperplasia of the organism, constituent tissues and is determined by post natal body size. It is influenced by factors like: ethnicity, climate, environment, nutrition, etc. The different stages or phases of growth are:

•  Prenatal Period
• Postnatal Period Infancy Childhood Adolescence Adulthood Senescence

1.   GROWTH MEASUREMENT AND ASSESSMENT TOOLS

The assessment and interpretation of growth studies requires standardized measurement procedures, trained personnel, the use of appropriate, regularly calibrated instruments and the collection of reliable data. It is important to use the proper equipment and standardized technique while taking any measurement. Equipment should be calibrated regularly while taking any measurements.

1.1 Anthropometry

The word ‘anthropometry’ is derived from the Greek word ‘anthropo’ meaning ‘human’ and the Greek word ‘metron’ meaning ‘measure’ (Ulajaszek, 1994). Anthropometry has been extensively used for the measurement of growth, assessment of health and nutritional risk especially in children. Growth measurements to assess

external dimensions of the body such as height, weight and subcutaneous fat are done using anthropometric methods. The field of anthropometry encompasses a variety of human body measurements including body weight, stature or height, recumbent length, skinfold thicknesses, circumferences which include head, waist, limb lengths, and breadths (shoulder, wrist, etc.). There are also indices and ratios which can be derived from these anthropometric measurements such as Body Mass Index (BMI), Waist Hip Ratio (WHR), Waist Height Ratio (WHtR), Appendicular Central Ratio (ACR), Grand Mean Thickness (GMT), etc. These body measurements are primary indicators for monitoring growth, health, nutritional status and provide information regarding future health potential (Roche & Sun, 2003). Understanding of body size is important at all ages and particularly at birth because of its association to morbidity and mortality in early infancy and its possible relationships to some diseases in adulthood.

The universal standardization of anthropometric measurements was started since the nineteenth century. Series of longitudinal growth studies have been conducted in America, Britain and other countries. A bibliography of 948 references were collected by research teams from growth studies in Belgium, Britain, France, Senegal, Sweden, Switzerland, Uganda and the USA after meeting every two years to originally discuss their methods and ultimately their results. An International Biological Project during the period 1962 to 1972 brought together scientists all over the world under the umbrella of research in ‘Human Biology’ (Cameron 2012). These gave rise to one of the standard texts in the human biological sciences known as IBP Handbook which was revised and renamed as Practical Human Biology and forms the source for many scientists who want to employ standard techniques to measure growth. Besides the standard techniques, there are some important qualities delineated 68 years ago by Aleš Hrdlička and still pertinent today which are good eyesight for distance and colour, freedom from halitosis and other unpleasant odours, sympathy, perseverance, orderliness, thorough honesty and carefulness. The researcher while measuring and collecting data should be careful of the sensibilities of his subjects, careful in technique, careful in reading the scale of his subject, careful in recording and capable of concentration in his work (Hrdlička, 1947).

The instruments used for body measurements are:

o   Stadiometer/ Anthropometer/ Infantometer: It is used to measure length and breadth measurements

o   Skinfold Calipers: It is used to measure skinfold thicknesses

o   Flexible Steel Tape: It is used to measure body circumferences

o   Weighing Scale: It is used to measure body weight

The various measurements and assessment tools that are used to measure growth are described as follows:

• Weight

During infancy digital weighing scale is recommended but a beam scale weight can also be used. The pan of the scale must be at least 100 cm long. A cloth is placed on the pan and the scale is calibrated across the range of expected weights using objects known as weights. The digital weighing scale for infants is used for children from 0-24 months. All scales should be calibrated whenever they are moved. The weight of an infant is obtained from the difference of the weight of the caregiver holding the infant and the caregiver without the infant. A subject who is able to stand without support is weighed using digital scale or a beam scale with movable weights. The subject is weighed with light clothing and without any accessories. Care should be taken not to weigh subjects after meals or weighed at least 1-2 hours after meals.

A Stadiometer is used to measure height/stature which measures the vertical distance from the vertex to floor. This apparatus consists of a vertical board with an attached metric rule and a movable horizontal headboard which is adjustable; the latter can be brought into contact with the most superior point on the head. The subject is barefoot or wears thin socks and minimal clothing so that the body positioning can be checked. The subjects stands on a flat surface in front of the vertical board with his/her weight distributed on both feet and the hands hanging freely with the palms facing inwards (See Figure 3). Stature instead of length is measured after 2 years of age who are able to stand unassisted (4B). Length of children below 2 years of age is measured with an infantometer (4A).

Another instrument used for measuring height/stature as well as transverse breadths of the body is Anthropometer. It consists of four segments which when joined together forms a rigid rod of 200 cm. There is a fixed sleeve on the top of the rod and also a movable sleeve with an adjustable graduated cross bar which registers the height measurements. The subject should be made to stand on a horizontal platform with his/her heels together and the head oriented in the Frankfurt Horizontal plane also known as FH plane or Eye Ear Plane.

Infantometer is used to measure the length of infants till they are able to stand upright on their own

• Head circumference

A flexible steel tape is used to measure the head circumference and the other girth measurements of the body. It is graduated in cm (See Figure 7). During early infancy, the head circumference is measured with the infant seated on the lap of the mother or caretaker. However, at older ages it is measured with the subject in the standard standing position. Hair clips, bands and other accessories on the hair are removed before the measurement is taken.

• Mid Upper Arm Circumference (MUAC)

The mid upper arm circumference is measured midway between the lateral tip of the acromial process of the scapula and the most proximal point on the olecranon process of the ulna. A flexible steel tape is used to measure the mid upper arm circumference (MUAC).

• Skinfolds

Skinfold thicknesses are measures of double folds of skin and subcutaneous adipose tissue at specific sites. Skinfold thicknesses are measured with the help of Skinfold calipers. It is recorded in mm. Skinfold thickness can be measured at different sites namely: subscapular skinfold (See Figure 2), Suprailiac skinfold, abdominal skinfold, calf medial skinfold, calf posterior skinfold, biceps skinfold, triceps skinfold, thigh skinfold, etc. The grand mean thickness (GMT) can be derived from the sum of the skinfold measurements divided by the number of skinfold sites.

1.1.1 Measurements generally used in growth studies

The general pattern of postnatal growth is quite similar from one individual to another, but there is considerable individual variability in size attained and rate of growth at different ages, with respect both to the body as a whole and to specific parts. Both the whole body and its parts, therefore, must be measured, and the study of growth is identical to a large extent with measurement. Breadth or width measurements are ordinarily taken across specific bone landmarks and therefore provide an indication of the robustness, or sturdiness of the skeleton. The commonly used skeletal breadths are biacromial breadth, bicondylar breadth, etc. Limb circumferences are occasionally used as indicators of relative muscularity. Skinfold thicknesses are indicators of subcutaneous fat, the portion of body fat located beneath the skin. Skinfolds can be measured at any number of body sites. Most often they are measured on the extremities and on the trunk, to provide information on the distribution of subcutaneous fat in different areas of the body. The most commonly used skinfold thicknesses are the triceps skinfold, the subscapular skinfold, medial calf skinfold, suprailiac skinfold, etc. Some measurements are useful during particular phase of growth. Head circumference, perhaps the most important, is taken on infants and children to monitor the physical development with age.

Besides, the body measurements, the maturity of a child can be assessed at a single examination using sexual, skeletal or dental criteria. Accurate assessments of maturity are important because misclassification of maturity levels can cause large errors in the interpretation of growth data.

o        Sexual maturity

Sexual maturity can be assessed from the development of pubic hair in each sex, the genitalia in males and the breasts in females. Sexual maturity can be evaluated from nude photographs, but this involves even more invasion of privacy and the possibility of misuse. Photographs allow the review of doubtful data, but it is difficult to recognize from photographs the first stage of pubic hair, the final stage of breast maturation and thinning of the scrotum. A physician usually assesses sexual maturity by direct inspection and it can also be done by self-assessment.

o        Eruption of teeth

Another way to measure growth is eruption of teeth but this is not very reliable as it varies from child to child. All the same, let us briefly discuss eruption too as an indicator of measuring growth. There are two sets of teeth in the human life i.e. the milk teeth and the permanent teeth. The different types of teeth are incisor, canine, premolar and molar which vary in size, shape and their locations in the jaws. These differences facilitate teeth to function together to help in chewing, speaking and smiling. They also give the face to have its shape and form. Figure 9 represents the development of tooth in humans. From infancy to childhood people generally have 20 primary (milk/baby) teeth, which often erupt around 6 months of age. The milk/baby teeth are then shed at various times during middle childhood. By the age of 21 years, all 32 of the permanent teeth have usually erupted. The knowledge of the eruption of teeth is one of the dimensions which envisage the growth and development of humans.

1.1.1.1 Inter-observer differences

Inter-observer differences are the differences between interpretations/observations of two or more individuals of the same measurement. It is one of the causes of anthropometric measurement error. The most commonly used measure of anthropometric measurement error is imprecision, which is largely due to observer error. Imprecision is the variability of repeated measurements and is due to intra and inter observer measurement differences. The greater the variability between repeated measurements of the same subject by one (intra observer differences) or two or more (inter observer differences) observers, the greater the imprecision and the lower the precision (Norton & Olds 1996). Hence the instruments/tools should be correctly postioned at the respective sites by the observer to avoid the inter or intra observer differences to the minimum. An example of correct measurement of skinfold thicknesses is illustrated in figure 10.

1.2 Clinical Growth Assessments

There are no standardized methods to measure children suffering from clinical conditions such as cerebral palsy, obesity, etc. However standard methods are applied if the child can stand, if not then recumbent and  anthropometric methods are recommended. Special equipment such as bed or wheelchair scales are used for measuring weight of handicapped children. Recumbent knee height with known errors is the best method for estimating stature of handicapped children. For measuring the knee height, both the knee and the ankle are positioned at 90o . The fixed blade of the sliding caliper is placed under the heel of the leg below the lateral malleolus of the fibula and the movable blade is moved to the anterior surface of the thigh above the condyles of the femur.

1.3 Body Composition Assessments

Direct and indirect methods are employed in assessing a child’s body composition. Direct methods include neutron activation, computed tomography and magnetic resonance imaging while indirect methods are measures of body weight and length, skinfolds or circumferences in mathematical models and bioelectrical impedance.

Density of fat varies little at any age but the density of fat free mass FFM varies depending on its hydration and the proportions of muscle and bone according to age, gender, race and level of maturation. Such inter individual differences increase errors in estimating body composition in children. However, multi compartment model is used for improving the accuracy of the assessment .The unavailability of reference data of children is one of the limitation of the utility of assessing body composition in children. Reference data for adolescents are available. Prediction equations for total body water and fat free mass (FFM) have been developed and are used for adolescents 12-19 years of age.

2.0 METHODS OF STUDYING GROWTH

There are different methods of studying human growth. Some important methods are as follows:

i) Cross -sectional method

ii) Longitudinal Method

iii) Mixed longitudinal method

iv) Extended longitudinal method

i   Cross- sectional method

In this method the study is completed by observing and measuring different individuals at different stages of growth, every individual is measured once only, and therefore, all the children at age 6, are different from those at age 5. Cross-sectional method is adequate for studying distributions of various measurements in different individuals at different ages and for constructing standards of growth attained.

ii  Longitudinal Method

It is the method of studying growth by observing and measuring the same individual for a long period, during his/her growth. In longitudinal study each child is measured at each age and therefore, all the children at age 8 are the same as those at age 7. A longitudinal study may extend over a number of years. Longitudinal studies may be for a short term covering a couple of years, and a full birth to maturity study in which children may be examined once in a year, twice in year, or more than two times every year from birth till 20 years. In this approach measurements are repeatedly done on the same individual or group of individuals. Longitudinal method is the best method to study the growth of any individual child or population. However, it is very necessary that the measurements taken must be correct and accurate.

Longitudinal data are preferable for estimating mean velocities of growth. In estimating the variability of the velocity from one year to another, longitudinal data are extremely necessary.

iii   Mixed longitudinal method

Mixed longitudinal is used when it is not possible to measure exactly the same group of children every year for a long period. In this method, some children may inevitably leave the study, and others, if that is desired may join it.

One particular type of mixed study is that in which a number of relatively short-term longitudinal groups are overlapped. Thus one might have groups of ages 0 to 6, 5 to 11, 10 to 16 and 15 to 20 years to cover the whole age range.

iv   Extended longitudinal method

In an extended longitudinal study, a whole series of measurements is available for each child. If these measurements are plotted against chronological age, a curve of growth is obtained. The slope of this ‘distance-traveled’ curve gives a picture of successive increment or growth velocities which may be based on weight, length and head circumference. The growth velocity curve or curve of first divergence is obtained by plotting the increments against age.

3.0 GROWTH CHARTS

Children’s growth is an important marker of their health and development. Both infant body size during the early years of life and infant growth velocity have been shown to be associated with risk of overweight and obesity in childhood and adulthood (Rolland-Cachera & Peneau 2011). Growth assessment is the single measurement that defines the health and nutritional status of children because disturbances in health and nutrition almost always affect growth (de Onis & Habitat 1996). Growth assessment involving the measurement of weight, length or height (and infants’ head circumference) followed by accurate plotting on a growth chart is quick, non-invasive and provides valuable information about the general health and well being of the child. At times it can be perceived by some health professionals as a low priority, as reflected by absence of functional equipment in some settings for weighing and measuring children (Stoner & Walker 2006). At other times parameters are recorded but not plotted onto growth charts resulting in missed opportunities for the early detection of health conditions related to altered growth. This is a matter of concern due to the increasing rate of childhood obesity globally. Growth assessment can be reassuring for parents if their child is gaining weight steadily; however monitoring too frequently or focusing on weight gain can lead to anxiety and unnecessary referral to secondary services (Freeman et al. 2006). Growth charts are commonly used to educate parents about their children’s growth with the help of health professionals and involve them in decisions on the management of altered growth patterns.

Growth charts show the growth of a reference population and are used for the assessment of individuals and groups of children. It shows progressive changes in height and weight of a child with age. Serial measurements of the child’s growth plotted on a growth chart are used to identify and assess patterns of growth. Single or ‘one-off’ measurements for individual children show only a child’s size, not their growth. Growth charts are an essential tool in the monitoring and assessment of children’s growth. The interpretation of childhood growth percentile tracking is dependent on the growth charts used. Hence it is important to be aware of the consequences of the methods used in the construction of growth charts when interpreting growth data in the clinical and epidemiological setting (Rolland-Cachera & Peneau 2011). Growth charts also serve as the primary tools for the identification of unusual growth. Growth charts may be calculated as percentiles in most cases and usually when the data are normally distributed it is appropriate to present the mean and selected standard deviation (SD) levels (Z scores). A Z or SD score may be positive or negative. A negative Z score indicates that it is below the mean SD and positive value indicates that it is above the mean.

a) Head Circumference Growth Pattern

• The head circumference measurements are used for estimating the growth of the brain. At birth, the head circumference of a term baby averages 34 cm. The head circumference grows most rapidly in the first year, 2 cm monthly in the first 3 months, 3 cm during the next 3 months, and 3 cm in the last 6 months. This means that the average head circumference is 44 cm at 6 months and 47 cm at 12 months of age. Thus, the head circumference grows by 12 cm during the first year.

b) Mid Upper Arm Circumference Growth Pattern

• The measurements of mid upper arm circumference (MUAC) are used for determining whether the child is well nourished or malnourished.
• The mid upper arm circumference increases fairly rapidly to about 16 cm by the age of one year. In the period 1 to 5 years, the mid upper arm circumference increases by only 1 cm. So, irrespective of age, the mid upper arm circumference of well nourished children ranges 16 -17 cm in the period 1-5 years. Conversely, if the mid upper arm circumference of a child of 1 to 5 years of age is less than 16 cm, that child has malnutrition and corrective intervention should be carried out

c) Length/ Height Growth Pattern

• An average term baby is 50 cm long. The length increases by 50% in the first year. In the second year, the average height growth is about 12 cm. The birth length doubles by 4 years of age. After the second year of age, the annual height growth averages 5-6 cm until the beginning of the adolescent growth spurt. Height growth stops at about the age of 18 years in girls and at the age of about 20 years in boys.
• After plotting the child’s height or length on a height chart, you should determine whether the growth pattern is normal. A normal growth pattern is parallel to the printed percentile lines.
• There are also weight for height charts and tables. Weight for height below the fifth percentile is a good indicator of acute under nutrition

3.1 Applications of Growth Charts

The standard method of developing a growth chart is to calculate the percentiles for each specified age range. Growth measurements are usually plotted on age and sex specific growth charts and recorded in tables. A comparison between the plotted data and reference percentiles will illustrate the approximate levels for the child or children relative to other children by matching age and sex. The accepted normal ranges are the 3rd and 97th percentiles in almost all countries but the 5th and 95th percentiles are used in the United States and sometimes the limits are ±2 Z in some countries (Roche & Sun, 2003). The values lying outside these limits are more likely to be associated with pathological conditions than values nearer the means or medians.

4.0 Why is Growth Assessment Necessary?

The assessment of growth and development is very helpful in finding out the state of health and nutrition of a child. It is the best general index of health and nutritional status of an individual child and a population. Continuous normal growth and development indicate a good state of health and nutrition of a child. Abnormal growth or growth failure is a symptom of disease. Hence, measurement of growth is an essential component of the physical examination. Anthropometric references for the infants and young children are among the most used tools for assessing pediatric well being (de Onis et al. 2004). Growth assessment also serves as a form of screening for growth disorders or health concerns related to growth. It can be used as early detection of malnutrition to prevent ill health and thus provide adequate nourishment. Growth assessment can be a reliable indicator for prevention of adult overweight and obesity. Table 2: Possible causes of abnormal child growth

4.1 Importance of Growth Monitoring

Health workers and parents should monitor the growth of children for the following reasons:

• For early detection of abnormal growth and development
• To facilitate the early treatment or correction of any conditions that may be causing abnormal growth and development.
• To provide an opportunity for giving health education and advice for the prevention of malnutrition
• Improve nutrition and overall health

4.1.1    Appendix

• Growth pattern over time is more important than a single measurement
• Weight & length or height measurements are health screening tools
• Growth is one sign of general health
• Many things affect a child’s growth and growth reflects family growth patterns
• Parents should focus on healthy eating & lifestyle habits rather than physical appearance
• Parents should focus on positive lifestyle habits and feeding or eating relationship
• Parents should model positive body image and respect child’s individuality
• Growth assessment should be considered as a tool to assess readiness for information and need to explore things further