1.2 Assessment of nutritional status

Question 1

Overview

Answer 1

This session starts by providing some contextual information on child growth before exploring different types of nutritional assessment. There are four main types of assessment each with different strengths and weaknesses; they can be easily remembered asABCD:Anthropometry – taking physical body measurements e.g., weight, height, mid-upper arm circumference (MUAC). Biochemical assessment – more invasive tests such as blood/urine tests for iron or iodine. Clinical assessment – physical examination for specific symptoms e.g., checking skin/eyes, assessing for bilateral oedema, dehydration, or ability to stand. And Dietary questionnaires – usually on food consumption such as food frequency or 24-hour recalls. These need to be carefully crafted and professionally conducted to minimize bias.

Question 2

Overview

Answer 2

Anthropometry is the most widely used method and the growth charts found in many countries ‘Under Five’ health books are examples of anthropometry. The growth of infants and children is monitored because: 1. Individual level - it is a very good indicator of both the nutritional status and general well-being of the child; and Population level - the nutritional status of children under 5 years population is used as a proxy indicator for the general health status of the whole population.

Question 3

Overview

Answer 3

Stunting is an often-used indicator for nutrition interventions as it reflects long term nutritional status. However, as it has many determinants, many factors need to improve in order to change stunting prevalence – including an improvement in the socio-economic situation and the public health environment. Stunting can take years (to generations) to reduce but there are many success stories e.g., Kenya.

Question 4

Learning objectives

Answer 4

After working through this session, you will be better able to: use nutritional terminology and the acronyms accurately; discuss the utility of different assessment methods and indicators of nutritional status; and discuss practical application of the indicators used to measure nutritional status in different population groups

Question 5

Key terms Acute malnutrition

Answer 5

A result of recent rapid weight loss or failure to gain weight. Often termed ‘wasting’. In children, it is measured using weight-for-height (WFH), the Mid Upper Arm Circumference (MUAC), BMI for age or weight-for-age (WFA).

Question 6

Key terms Anthropometry

Answer 6

Body measurements such as weight, height/length and MUAC

Question 7

Key terms Bilateral oedema

Answer 7

Fluid retention as indicated by swelling on both sides of the body, often in the legs, ankles and feet. Bilateral oedema is indicative of severe acute malnutrition (SAM) and poorer prognosis.

Question 8

Key terms BMI

Answer 8

Body mass index is typically used to indicate overweight and obesity in adults.BMI = weight kg/height m2

Question 9

Key terms Chronic malnutrition

Answer 9

A result of a long-term marginal or deficient food intake that prevents optimal growth leading to a height deficit in relation to age. Often termed ‘stunting’. In adults BMI, in children height-for-age (HFA) is used as an indicator.

Question 10

Key terms MUAC

Answer 10

The mid upper arm circumference is used to indicate wasting. It is sensitive to changes in lean body mass and can also be used in pregnant women and the elderly.

Question 11

Key terms Percentile

Answer 11

The percentile is the rank position of an individual on a given reference distribution, stated in terms of what percentage of the group the individual equals or exceeds. Percentiles can be thought of as the percentage of children in the reference population below the equivalent cut-off i.e., 97thpercentile, 97% of individuals lie below this value and 3% above. The use of percentiles has largely been replaced by the z-score but may be in use in some contexts.

Question 12

Key terms Stunting

Answer 12

Height deficit in relation to age; measured in children by height-for-age (HFA). Stunting develops over time and is also known as chronic undernutrition.

Question 13

Key terms Underweight

Answer 13

Underweight refers to either wasting or stunting or a combination of both and is measured using weight-for-age (WFA).

Question 14

Key terms Wasting

Answer 14

Develops as a result of recent rapid weight loss or a failure to gain weight and indicates acute undernutrition. In children, it is measured using weight-for-height (WFH) or the MUAC. In adults the BMI or MUAC are used.

Question 15

Key terms Z-score

Answer 15

An epidemiological term used as an indicator of nutritional status. Z-score (or standard deviation unit, SD) is defined as the difference between the value for an individual and the median value of the reference population of the same age or height, divided by the standard deviation of the reference population. A z-score of 0 equals the median of the reference population.

Question 16

Introduction to child growth

Answer 16

To achieve their genetic potential an infant requires substantial levels of energy and other nutrients. These levels are at their maximum in the first few months of life. Energy requirements in the first year are proportionally 3 times higher than in adults (100 kcal/kg body weight for infants as opposed to 30 kcal/kg in adults).

Question 17

Introduction to child growth

Answer 17

The growth rate of infants is the result of the interaction of genetic and environmental factors, of which access to food is the most important environmental factor. Where possible, newborn infants should be exclusively breast fed to benefit from the strong immunological protection it provides. Exclusive breastfeeding results in a decreased incidence and severity of infectious diseases and in particular of diarrhoea and acute respiratory infections. In addition, breast feeding protects against the development of obesity and non-communicable diseases in later life. Breastfed babies grow faster than bottle fed in the first six months of life. WHO recommends exclusive breastfeeding for the first 6 months of life.

Question 18

Introduction to child growth

Answer 18

As children continue to grow, their weight and height increase, at varying speeds, until adulthood. Standardised growth charts are readily available to facilitate growth monitoring. If children are living in unfavourable environments growth falters as undernutrition develops or alternatively poor-quality diets, in excess of need, can lead to the development of overweight and obesity.

Question 19

Anthropometry

Answer 19

Anthropometry is used to measure malnutrition in individuals and in populations; adults and children. It includes a range of different indicators such as weight and MUAC.

Question 20

Anthropometry Anthropometry in the Child

Answer 20

The first anthropometric measure is birthweight which is a direct measure of a new-born’s nutritional and health status. A low birth weight (LBW=<2.5 kg) infant, is at higher risk of foetal and neonatal mortality and morbidity from infectious disease, inhibited growth and cognitive development. LBW is also associated with non-communicable disease later in life.

Question 21

Anthropometry

Answer 21

Infants less than 6 months old are usually only weighed to monitor their growth. Further assessment relies primarily on clinical signs such as oedema, visible wasting, too weak to suckle, not gaining weight despite feeding. Young infants are vulnerable and the WHO’s MAMI (Management of acute malnutrition in infants) 2010 outlines best practice.

Question 22

Anthropometry

Answer 22

Indicators can be used to detect acute or chronic malnutrition in the individual and this is determined if the child is above or below the respective cut off. However, frequency of an indicator below a respective cut off is used to detect a problem and if it is one of significance. The nutritional indicators commonly calculated for children 6-59 months are:

Question 23

Anthropometry Weight-for-height(Wt/Ht or WFH )

Answer 23

a measure of wasting or acute malnutrition.Global acute malnutrition (GAM) -is defined as WFH <-2 z scores. Moderate acute malnutrition (MAM) -is defined as WFH -3 to -2 z scores. Severe acute malnutrition (SAM) -is defined as WFH <-3 z scores

Question 24

Anthropometry Height-for-age(Ht/age or HFA)

Answer 24

a measure of stunting or chronic undernutrition. Moderate chronic malnutrition is diagnosed if a child is <-2 z-scores. Severe chronic malnutrition is defined as HFA <-3 z-scores.

Question 25

Anthropometry Weight-for-age(Wt/age or WFA)

Answer 25

a measure of underweight or wasting and stunting combined for children to 10 years. It is the most widely collected indicator but cannot distinguish between a tall thin or a short but heavier child so needs to be considered with other assessment. Moderate underweight is defined as WFA -3 to -2 z scores

Question 26

Anthropometry MUAC

Answer 26

a measure of wasting or severe acute malnutrition.Moderate acute malnutrition <12.5cm, Severe acute malnutrition =<11.5cm. MUAC measurements correlate well with BMI and is replacing BMI in some settings. MUAC is also tightly, negatively associated with increased mortality below 11.5cm.

Question 27

Anthropometry Bilateral oedema

Answer 27

is indicative of severe acute malnutrition

Question 28

Anthropometry BMI for age

Answer 28

a measure of overweight and obesity.Overweight: >+1 z-scores Obesity: >+2 z-scores. It is important to understand the distinction between ‘chronic’ and ‘acute’ undernutrition as they are different syndromes with very different cut offs to indicate a public health problem. For example; 19% prevalence of stunting is classified aslowby WHO 19% prevalence of wasting it is classified asvery highand an emergency situation. Acute and chronic malnutrition can occur together and, in this situation, they have cumulative effects in terms of morbidity and mortality on the child (Blacket al., 2008).

Question 29

Activity 1 Answer the questions below relating to Figure 1; which illustrates the standard reference growth chart for girl’s weight for age from birth to 2 years in z-scores. What is the significance of the <-2 z-scores line? What does <-3 z-scores indicate?

Answer 29

These are the cut offs for diagnosis of undernutrition, <-2 z-scores, and severe undernutrition <-3 z-scores.

Question 30

Activity 1 Weight for age is widely collected globally and is the common method for child growth monitoring. What sort of practical and cultural limitations do you think there might be?

Answer 30

The precise age of children is often unknown. Weight for age does not differentiate between a short fat child and a tall undernourished one. It requires a child to be undressed which is not acceptable to some cultures.

Question 31

Activity 1 How would you classify an 8-month girl who is 5.8 kg?

Answer 31

The child is classified as moderately-severely underweight. It is probable that the infant will also be wasted although this cannot be concluded from the information provided. In some contexts, wasting is more likely to illicit a response from health systems. At 8 months the child is extremely vulnerable and in need of support, the focus of which should be the continuation/re-lactation of breast feeding-if the mother is available-along with appropriate support for complementary feeding. Any underlying clinical pathologies should also be addressed.

Question 32

Activity 1 Why are international standards important?

Answer 32

The international standards for height and weight provide a standard for comparison that can be used in all studies. This means that data collected in one part of the world is directly comparable elsewhere. The standards place international comparisons on a secure basis.

Question 33

Activity 2 What do you understand by the 25th percentile?

Answer 33

The 25th percentile is the line below which 25% of the children are found. Thus 75% of normal children are taller than the 25th percentile.

Question 34

Activity 2 How does height change in relation to age in this group?

Answer 34

This standard reference chart shows that infants should have a rapid increase in length/height in the first 2 years of life which then slows and, at the population level, the growth rate is almost constant from 2-5 years of age.

Question 35

Activity 2 Does this pattern represent an individual’s growth path?

Answer 35

The chart does not reflect an individual infants growth it reflects a populations growth up to 5 years of age. An individual’s growth may be erratic due to growth spurts or environmental factors such as an opportunistic infection, poor food supply.

Question 36

Activity 2 What would affect height over time?

Answer 36

Growth in length/height in infancy requires significant amounts of energy (approximately 100 kcal/kg/day as opposed to 30 kcal/kg/day in adults) so an adequate diet is paramount.

Question 37

Activity 3 Figure 3 illustrates the change in BMI-for-age of girls from age 5 through their adolescence to adulthood at 19 years. Study figure 3 and then answer the questions below. Why do you think that the differences between the z-scores diverge from about 9 years onwards?

Answer 37

Some of the differences are attributable to changes in the body related to puberty. It also reflects that children and adults can have different statures and body shapes and still be considered healthy. Different body shapes can occur both within and between different racial groups.

Question 38

Activity 3 How would you classify a 6-year-old girl who is 31 kg in weight and 1.2 m in height? Use the BMI formula given in ‘key terms’ to initially calculate the child’s BMI.

Answer 38

This child would be categorised as obese with a BMI of 21.53 at 6 years of age. BMI = kg/(m)(m) = 31/(1.2)(1.2) = 21.53

Question 39

Anthropometry Anthropometry in the adult

Answer 39

The nutritional status of adults is typically assessed using the body mass index (BMI) and the cut offs for both over and undernutrition are presented in Table 1.

Question 40

Anthropometry Anthropometry in the adult

Answer 40

While the BMI is a good standardised method it doesn’t take into account the body composition of lean vs fat tissue and some more extreme body shapes can be inaccurately classified. For example: weightlifters with a high muscle mass may be classed as obese or lean marathon runners as undernourished.

Question 41

Anthropometry Anthropometry in the adult

Answer 41

International guidelines (Collinset al., 2000) recommend that BMI should be adjusted for sitting height-to-standing height ratio (SSR or SH/S) or the Cormic index. This index accounts for differing lengths of leg between populations, for example the Dinka (in South Sudan), who tend to be very long legged compared to other populations. While this is recognized technically, this adjustment is not commonly practiced.

Question 42

Anthropometry Anthropometry in the adult

Answer 42

The BMI is widely used to assess adults but waist measurement and the waist-to-hip ratio are also gaining currency (Kragelund and Omland, 2005), but these are more personally invasive and require training to measure accurately. The waist-to-hip ratio measures central adiposity (apple vs pear shaped) and like the waist measurement is highly sensitive to risk of CHD.

Question 43

Anthropometry Anthropometry in the adult

Answer 43

In pregnant women, weightis used to monitor for appropriate weight gain whereas the mid upper arm circumference (MUAC) is used to measure undernutrition due to its sensitivity to changes in lean muscle tissue. The BMI is not easily used in pregnant women due fluid and weight changes.

Question 44

Anthropometry Anthropometry in the adult

Answer 44

A MUAC cut-off of <210 mm has been used to identify undernourished women however this is probably too low as it has been associated with a significant increase in low birth weight (Mohantyet al., 2006). A cut off of <230mm is also used in some contexts but globally accepted cut offs haven’t yet been established.

Question 45

Anthropometry Anthropometry and the elderly

Answer 45

The nutritional status of the elderly has not been as well researched as other age groups. In addition, some elderly become disabled, bedridden or unable to stand straight so are particularly difficult group to assess anthropometrically. People age differently and but typically reductions in height (due to compression of the vertebrae and stooping) occur with age. A typical rate of 1 cm to 2 cm per decade is lost after the age of 40, and even more rapidly in older ages.

Question 46

Anthropometry Anthropometry and the elderly

Answer 46

There are no internationally agreed anthropometric indicators to assess the nutritional status of the elderly. Padilla et al (2021) give an overview of anthropometric methods that can be used in elderly populations.

Question 47

Anthropometry Anthropometry and the elderly

Answer 47

The MUAC is overlooked by Padilla but MUAC is sensitive to lean body mass changes and has been used to indicate undernutrition in the elderly. Cut offs of 161-185 mm have been used in practice.

Question 48

Anthropometry Anthropometry and the elderly

Answer 48

Research suggests that measures such as the demi-span (arm length from base of middle/ring finders to the sterna notch on the torso), arm span and knee height can be used to estimate height in older people.

Question 49

Anthropometry Anthropometry and the elderly

Answer 49

In the absence of definitive guidance, a combination of assessment methods – anthropometry, biochemical assessment, dietary questionnaires and clinical assessment - is often used. The mini nutritional assessment (MNA) is one validated example (Guigozet al., 2002) for use with older people.

Question 50

Biochemical assessment of micronutrient status

Answer 50

The assessment of micronutrients status is either direct via clinical or biochemical assessment or indirect via assessment of nutrient intake.Figure 4 provides an overview of the direct assessment of some vitamins and minerals. The notes in the table are taken from Black (2013).

Question 51

Biochemical assessment of people with infections

Answer 51

An infecting pathogen leads to the immune system launching an initial acute phase response. An important part of the acute phase response is the production of the acute phase proteins (APP) and one of their tasks is the binding to or sequestration of some micronutrients (vitamin A and Fe in particular) in the tissues. This is to reduce their availability to the pathogen. This means that biochemical assessment of serum retinol and ferritin levels during an infection gives unreliable results. Serum retinol assessment will underestimate the true vitamin A status, while serum ferritin will overestimate the true iron status. There is not yet a consensus on how adjustments should be applied but the presence of an infection should be considered during interpretation of results.

Question 52

Assessment of dietary intake

Answer 52

There are a number of established methods to assess dietary intakes which have differing levels of complexity and accuracy. These include food diaries, 24-hour recall and food frequency questionnaires, all are subject to sources of error which can be minimized by using trained nutritionists/dietitians with good communication skills. This is important as many people often do not remember what or how much they eat.

Question 53

Assessment of dietary intake

Answer 53

Food intake and dietary patterns can change according to season, trends in price and many other factors so a significant number of days needs to be covered to assess habitual dietary intake. A week is adequate to assess energy intake, as this tends to be relatively constant, but micronutrients such as iron or vitamin C require 2 weeks or more to be assessed accurately. Other challenges are that:the nutrient content of foods is not constant and can be subject to much variability; not all populations have individual portions but may share meals from one pot; specific micronutrients are not widely distributed in foods and thereby not eaten every day; and food intake does not equal food absorption. An estimated absorption is often used, but there can be great inter-individual variability, and estimates are often very inaccurate. For example, iron absorption is enhanced in anaemia and inhibited by phytates in the food; beta-carotene is much better absorbed from some vegetables than from others and the absorption level also depends on the manner of preparation.

Question 54

Assessment of dietary intake

Answer 54

Food diariescan be a useful way to assess dietary intake but are dependent on high levels of both literacy and the participant’s motivation if they are to provide an accurate reflection of macro and micronutrient intake. Individuals are required to record all food consumed and or estimate all portion sizes for a period of time, often a week or more. The investigator then needs to identify each food item, quantify the portion size and calculate the nutrient content using appropriate food tables. There are published food tables on-line and in hard copy, but proprietary software packages can streamline the processes significantly however they require a good level of computer access and literacy.

Question 55

Assessment of dietary intake

Answer 55

Another method of estimating food intake is by using a24-hour recallwhich involves a trained investigator interviewing individuals about food consumption during the previous day – to obtain an accurate level of detail on ingredients, cooking methods and portion sizes. This exercise typically takes 30 minutes or more. This method tends to yield lower estimates of intake than using a food diary and this may in part due to poor short-term memory.

Question 56

Assessment of dietary intake

Answer 56

The use offood frequency questionnaires(FFQ) is less time consuming but also requires careful data handling. FFQ are becoming increasingly common practice; their questions also revolve around the foods consumed over a fixed period of time but focus on the food groups consumed e.g., portions of ‘legumes, nuts or seeds’ or ‘red meat’ or ‘milk and milk products’. One FFQ designed for use internationally and that has been validated is the Individual Dietary Diversity Score (IDDS) produced by FAO/FANTA 2011.

Question 57

Activity 4 Influences on nutritional status. Figure 5 (redrawn from Floodet al.) compares the heights of two groups of Marine Society recruits to growth reference charts. The Marine Society was founded in 1756 to train seafarers and maintain records. They recruited from a cross-section of the working classes. What does the figure show?

Answer 57

The figure shows that in both 1825 and 1787 the Marine Society recruits were shorter than the modern standard. In both years they fell below the 3rd percentile of the modern standard and so can be considered as severely stunted. Conditions seemed to have improved between 1787 and 1825 so that the 1825 groups were taller though still stunted.

Question 58

Activity 5 Social class influences nutritional status. This is unsurprising as the richer elements of society have access to more and better-quality food. Figure 6 shows the influence of social class on the height of children in Nigeria compared to the international standard. What do the data show?

Answer 58

The data show that in both Ibadan and Lagos the children of professional people grow in line with the international standards achieving at least 50th percentile in terms of height. Growth of the children of skilled workers in Lagos was comparatively less than that of the children of professionals but approached the 50 percentile line. However, the growth of children from the slums was depressed in both cities.

Question 59

Activity 5 How do the social conditions compare with those in the 18th and 19th century England and Wales?

Answer 59

It can be argued that the data from Ibadan and Lagos shows marginal stunting among the children from the slums. However, the stunting among the Marine Society recruits (Figure 5) is much more marked. It seems likely that social conditions in the slums of Nigeria are better than those of 18th and 19th century England and Wales.

Question 60

Summary

Answer 60

1 The most common indicators of undernutrition in children are MUAC, Ht/age, Wt/age, Wt/Ht. Bilateral oedema is an indicator of severe acute malnutrition in all population groups. MUAC is rapidly becoming accepted as an indicator of acute malnutrition in pregnant women and the elderly. 2 Stunting can be used as a proxy indicator for health and poverty in the long term. 3 International child growth standards reference charts provide a standard for comparison that are used in all studies.4 Assessment of micronutrient status tends to use a clinical and/ or biochemical assessment method.5 Food diaries, recall and food frequency questionnaires can be useful tools to assess food intake but require the use of skilled, trained personnel.

Question 61

Question 1 Which of these statements about biochemical tests for micronutrient malnutrition is true? a) A biochemical test is always better than using clinical signs. b) Easy to do biochemical tests are available for all micronutrient deficiencies. c) Biochemical tests can be useful for confirming a diagnosis and for measuring the extent of sub-clinical deficiency.

Answer 61

c) Biochemical tests are very useful but they can be expensive and are not readily available in many countries.

Question 62

Question 2 Which of the following indicators are used to assess malnutrition in children under 5? a) BMI b) Weight-for-height c) MUAC d) Height-for-age

Answer 62

b), c) and d) are used to assess undernutrition.BMI/age is used in children under 5 for assessing overweight and obesity.

Question 63

Question 3 Which of the following can cause anaemia? a) Acute respiratory infections b) Diarrhoea c) Malaria d) Measles

Answer 63

c) Malaria causes haemolysis and subsequent iron losses.

Question 64

Question 4 Goitre is a clinical sign of which micronutrient deficiency? a) Vitamin A b) Iron c) Iodine

Answer 64

c) Iodine.

Question 65

Question 5 Which disease greatly increases the risk of vitamin A deficiency and its associated blindness and mortality? a) Acute respiratory infections b) Diarrhoea c) Malaria d) Measles

Answer 65

d) Measles causes a loss of vitamin A, alongside other complications, leading to increased blindness and mortality if not adequately addressed with vitamin A supplements.