Nutritional assessment system BY SAJIB REZA

1. Nutritional
Assessment System
Md . Sajib Reza
Lecturer
Department of Food technology and Nutritional Science
Mawlana Bhashani Science and Technology university
Tangail-1902, Bangladesh
Email: sajib.ftns2010@gmail.Com

2. Nutritional assessment … …
• Nutritional assessment can be defined as
“The interpretation of information from dietary, laboratory,
anthropometric and clinical studies used to determine the nutritional
status of individuals or population groups as influenced by the intake
and utilization of nutrients”. (Gibson, 2005)
• “Nutritional assessment is the systematic process of collecting and
interpreting information in order to make decisions about the
nature and cause of nutrition related health issues that affect an
individual” (British Dietetic Association (BDA), 2012).

3. The importance of nutritional assessment …. ….
Health care providers assess clients’ nutritional status for many reasons:
• To identify people at risk of malnutrition for early intervention or referral
before they become malnourished
• To identify malnourished clients for treatment— malnourished people who are
not treated early have longer hospital stays, slower recovery from infection and
complications, and higher morbidity and mortality
• To track child growth
• To identify medical complications that affect the body’s ability to digest food
and utilize nutrients
• To detect practices that can increase the risk of malnutrition and infection
• To inform nutrition education and counseling
• To establish appropriate nutrition care plans

4. Forms of nutritional assessment system … …
Four Forms of nutritional assessment system :
1. Nutrition Surveys 2. Nutrition Surveillance
3. Nutrition Screening 4. Nutrition Intervention
1. Nutrition surveys:
✓ A survey is a method used for collecting data from a predefined group of
respondents to gain information and insights into various topics of interest.
✓ Cross-sectional Nutrition Survey (at one specific point in time)
✓ establish baseline nutritional data
✓ determine the overall nutritional status of the population
✓ identify and describe population subgroups "at risk" for chronic malnutrition
✓ identify acute malnutrition
✓ provide information on the possible causes of malnutrition
✓ first step in an investigation

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2. Nutrition surveillance:
A continuous, systematic collection, analysis and interpretation of the dietary
intake and nutritional status of a population or selected population groups
using a variety of data-collection methods.
❑ ultimate goal is to provide regular and updated information on the nutritional
conditions of a population and the influencing factors, lead to policy
formulation and action planning.
❑ continuous or ongoing monitoring over an extended period of time
❑ sometimes merges with “nutrition monitoring”

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3. Nutrition Screening:
If a detailed nutrition assessment is difficult, Nutrition screening is used to
identify patients who are malnourished or at risk of being malnourished.
➢Nutritional assessments are more in-depth (measurements include dietary
intake, medical history, physical examination, anthropometric measures etc)
than screeners.
➢screeners are easy, simple and cheap, less time consuming, and that can be
applied rapidly on a large scale.
➢screening determines - the risk of being malnourished
➢ - the presence of malnutrition
➢Example: MNA (mini nutritional assessment) for hospitalized elder person
Sajib Reza

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4. Nutrition interventions:
Planned actions intended to positively change a nutrition related behavior, environmental
condition, or aspect of health status for an individual, target group, or the community at large.
➢target population subgroups identified as "at-risk" during nutrition surveys or by nutrition
screening
➢Two components: planning and implementation
➢Three types of nutrition interventions: supplementation, fortification, and dietary approaches.
Fortification: adding vitamins and minerals to commonly consumed foods during processing to
increase their nutritional value. e.g. iodine in salt
Supplementation: deliver nutrients that may not be consumed in sufficient quantities. E.g. iron Tb
Dietary approaches: purpose of dietary approaches is to resolve or improve the nutrition
problem by provision of advice, education or delivery of the food component of a specific diet or
meal plan.

8. Elements of Nutritional assessment methods: …. ….
• These methods are -
1. Dietary 2. Laboratory 3. Anthropometric 4. Clinical method
1. Dietary methods:
➢ The first stage of any nutritional deficiency is identified by dietary assessment
methods
➢ The dietary intake of one or more nutrients is inadequate. Because of -
1. A primary deficiency (low levels in the diet)
2. A secondary deficiency (such as certain drugs, dietary components, or disease states
interfere with the ingestion, absorption, transport, utilization, or excretion of the
nutrient)

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2. Laboratory methods:
Include both static biochemical and functional tests.
❑ Biochemical tests measures, biological fluids (serum, blood) or tissues or the urinary
excretion rate of the nutrient or its metabolite. (e.g. serum vit-A >0.7 ϻ mol/L)
❑Useful for identifying the second and third stages in the development of a nutritional
deficiency
❑ When the body fluid levels, become gradually depleted of the nutrient
❖ Functional tests include physiological or behavioral tests
❖ Used to detect the later stages in the development of a nutritional deficiency

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3. Anthropometric methods:
✓Involve measurements of the physical dimensions and gross composition of the body.
✓Measurements vary with age and sometimes with sex and race and degree of nutrition.
✓Useful where chronic imbalances of protein and energy are likely to have occurred.
✓Can detect moderate and severe degrees of malnutrition
✓Providing information on past nutritional history
✓Measurements can be performed relatively quickly, easily, and reliably using
portable equipment
✓Cannot be used to identify specific nutrient deficiency states

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• 4. Clinical methods:
• Medical history and Physical examination are the clinical methods
• Used to detect signs (i.e., observations made by a qualified examiner) and symptoms
(i.e., manifestations reported by the patient) associated with malnutrition
• Signs and symptoms are often nonspecific
• Only develop during the advanced stages of nutritional depletion
• Diagnosis should not rely exclusively on clinical methods
• Laboratory methods should also be included as an adjunct to clinical assessment
Sajib Reza

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5. Ecological factors:
❑ Other factors known to influence the nutritional status of
individuals or populations
❑ Including any relevant socioeconomic and demographic
variable
❑ Variables may include-
▪ household composition,
▪ education,
▪ literacy,
▪ ethnicity,
▪ religion,
▪ income,
▪ employment,
▪ material resources,
▪ water supply and household sanitation,
▪ access to health and
▪ agricultural services,
▪ land ownership
5. Ecological factors:
▪ food prices,
▪ the adequacy of food preparation equipment,
▪ the degree of food reserves,
▪ cash earning opportunities,
▪ the percentage of the house hold income spent
on certain foods such as animal foods, fruits, and
vegetables
▪ health and vital statistics
▪ access to good source of drinking water,
▪ the proportion of children immunized,
▪ the proportion of infants born with a low birth
weight,
▪ the percentage of mothers breast feeding, and
age
▪ causes of specific mortality rates
▪ birth order over seven,
▪ breakdown of marriage,
▪ death of either parent,
▪ episodes of infectious diseases

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14. Nutritional assessment indices and indicators …. ….
❑Raw measurements alone have no meaning unless they are related to the age or sex of an
individual (WHO, 1995)
❑Raw measurements derived from dietary, anthropometric, laboratory, and clinical methods are
often combined to form "indices".
❑“An index or indices is a combination of two measurements or one measurements plus
the person’s age.”
❑Examples of such combinations include -
✓ height-for age (an index used for assessing stunting),
✓ Weight-for-age (an index used in growth monitoring, wasting),
✓ nutrient density (i.e., nutrient intake per mega joule),
✓ body mass index (weight/height2),
✓ mean cell volume (i.e. hematocrit /red blood cell count) etc.

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• Indicators:
Indices are often evaluated at the population level by comparison with
predetermined reference limits or cut off points.
When used in this way, the index and its associated reference limit or cutoff becomes an
"indicator,“
“An indicator is an index combined with specific cut-off values that help to determine
whether a child is underweight or malnourished”
For example, a child whose weight for age, or weight for height, falls below the cut-off
values is considered to be underweight or malnourished.”
Index Cut-off value based on standard
deviation (SD)/percentage
What it indicates
Weight-for-age Less than -2 and more than -3 Moderate underweight
Weight-for-age Less than -3 Severe underweight
Height-for-age Less than -2 and more than -3 (i.e.
70–79.99% of the norm)
Moderate acute
malnutrition (MAM)
Height-for-age Less than -3 (i.e. less than 70% of the
norm) and/or bilateral pitting oedema
Severe acute malnutrition
(SAM)
BMI cut-offs for adults over 20 years
BMI range Diagnosis
<16 Underweight (grade 3 thinness)
16-16.99 Underweight (grade 2 thinness)
17-18.49 Underweight (grade 1 thinness)
18.5-24.99 Normal range
25.0-29.99 Over-weight (Pre –obese)
>30 Obese

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The critical attributes of the indicators required to meet these
objectives
• Indicators should be chosen carefully in relation to both the study objectives and their
attributes. They meet a variety of objectives.
• Required informational content
❑ Prevent malnutrition
▪ Indicate risk of future malnutrition or its consequences.
▪ Predict benefit from intervention
❑ Treat malnutrition
▪ Indicate harm from past malnutrition.
▪ Predict benefit from intervention
❑ Treat consequences
▪ Indicate harm from past malnutrition.
❑ Evaluate treatment
▪ Indicate responsiveness to intervention or determinant
❑ Promote nutrition education
▪ Indicate normalcy
Sajib Reza

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18. Evaluation of nutritional assessment indices …. ….
• Nutritional assessment indices can be evaluated by
➢ comparison with a distribution of reference values
➢ compared with either predetermined reference limits drawn from the
reference distribution or cutoff points
1. Reference distribution:
• Healthy (reference) individuals sampled during a nationally
representative survey
• Reference population sampled from healthy individuals
• Reference sample group is drawn from the reference population
• Reference values are obtained from the reference sample group.
• The distribution of these reference values forms the reference
distribution.
• Reference limits drawn from the reference distribution
• Reference limits define the reference interval
• Example: BMI (healthy/normal: 18.5-24.99)

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2. Reference limits:
• The reference distribution can also be used to derive reference limits and a reference
interval.
• Two reference limits are usually defined, and the interval between and including
them is termed the "reference interval.“
• For anthropometric growth indices in industrialized countries, the 3rd or 5th and 95th
or 97th percentile are frequently the reference limit used to designate individual with
unusually low or unusually high anthropometric indices
• whereas in low-income countries, reference limits based on standard deviation score
(Z-core) are preferred.

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3. Cutoff points -
• Are Nutritional assessment indices and low body stores, functional impairment or
clinical sign of deficiency.
• Their use is less frequent than that of reference limits because information relating
tests and sign of deficiency is often not available.
• Cutoff points may vary with the local setting, may vary area to area.
• Sometimes more than one cutoff point is selected.
• For example, for body mass index (BMI), two cutoff are often used to define over
nutrition in adult (BMI >25 over weight, BMI >30 obesity),
BMI cut-offs for adults over 20 years
BMI range Diagnosis
<16 Underweight (grade 3 thinness)
16-16.99 Underweight (grade 2 thinness)
17-18.49 Underweight (grade 1 thinness)
18.5-24.99 Normal range
25.0-29.99 Over-weight (Pre –obese)
>30 Obese
Sajib Reza

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• Trigger levels
• In population studies, cutoff points may be combined with trigger levels to set the
level of an index (or indicator) or combination of indices
• at which a public health problem exists of a specified level of concern
• Trigger levels may highlight regions or populations, where specific nutrient
deficiencies are likely to occur, or may serve to monitor and evaluate intervention
programs

22. The design of nutritional assessment systems:…. ….
• The design of the nutritional assessment system is critical. Components are-
1. Study objectives
2. Sampling protocols
3. Calculating sample size
4. Validity
5. Reproducibility or precision or reliability
6. Accuracy
7. Random errors
8. Systematic errors or bias
9. Confounding
10. Sensitivity
11. Specificity
12. Prevalence
13. Predictive value
14. Ethical issues
15. Additional factors

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• 1. Study objectives
Possible objectives may include:
1) Determining the overall nutritional status of a population or sub population
2) Identifying areas, populations, or sub populations at risk of chronic malnutrition
3) Characterizing the extent and nature of the malnutrition within the population or sub
population (Cross-sectional survey)
4) Identifying the possible causes of malnutrition within the population or subpopulation
5) Designing appropriate intervention programs for high-risk populations or subpopulations
6) Monitoring the progress of changing nutritional, health, or socioeconomic influences,
including intervention programs (surveillance)
7) Evaluating the efficacy and effectiveness of intervention programs (Nutrition
intervention)
8) Tracking progress toward the attainment of long-range goals

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2. Sampling protocols
❑Nutritional assessment systems target a large population - city, province, or country
❑Practically a limited number of individuals can actually be studied
❑These individuals must be chosen carefully
❑major factor influencing choice of sampling protocol is availability of sampling frame
(The list of individuals in the population, district, village or school or of districts)
❑Additional factors are time, resources, and logistical constraints
❑When sampling frame is not available – non probability sampling methods
(purposive sampling, convenience sampling, and quota sampling)
❑When sampling frame is available - probability sampling methods (simple random
sampling, stratified random sampling, and multistage sampling)

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3. Calculating sample size
• Sample size refers to the number of participants or observations included in a study from
population by using a sampling method.
• The sample size depends on the study objective, nature and scope of the study, and the expected
outcomes.
• Take assistance from a statistician or sample size calculator (e.g. Rao soft)
• The formula below used to determine the minimum sample size for the cross sectional study:

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4. Validity
❑ Refers how accurately an instrument or test or methods actually measuring what it
is supposed to be measuring.
❑ Indicates the accuracy of a measure whether the results really do represent what
they are supposed to measure/strength
❑ Describes the adequacy with which any measurement, index, or indicator reflects
what it is intended to measure.
• For example, if information on the long-term nutritional status of an individual is
required, the dietary measurement (e.g. 3 or 7 days) should provide a valid
reflection of the true "usual" nutrient intake rather than the intake over a single day.
(24 hour recall)
Sajib Reza

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5. Reproducibility or precision or reliability
❑ The ability of an instrument or methods to create consistent or same results each
time it is used under the same condition with the same subjects
❑ Reliability refers to the consistency of a measure / Repeatability
❑ If the same result can be consistently achieved by using the same methods under
the same circumstances, the measurement is considered reliable.
❑ Example include: A doctor uses a symptom questionnaire to diagnose a patient
with a long-term medical condition. Several different doctors use the same
questionnaire with the same type patient but give different diagnoses. This
indicates that the questionnaire has low reliability as a measure of the condition.

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6. Accuracy
❑“accuracy" is the extent to which the measurement is close to the true value
❑ It indicate that a measurement can be reproducible or precise
❑ inaccurate-when there is a systematic bias in the measurements.
❑ Accuracy in measurements is necessary for high reproducibility

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7. Random errors
Are unknown and unpredictable changes in the experiment caused by some factors which
vary from one measurement to another
❑ These changes occur in measuring instruments or in environmental conditions.
❑ Generate a deviation from the correct result
❑ They reduce the precision of a measurement. Three main sources of random error:
1) lndividua1 biological variation - for certain biochemical measurements, such as serum
iron. which are larger within subject variation.
2) Sampling error - collection of food samples for nutrient analysis, selection of individual
or person (can reduce by increase the sample size)
3) Measurement error - variations in the measuring and recording process. E.g. for
recording 24-h dietary recalls the measurement of the actual amounts of the foods
consumed is challenging.

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8. Systematic errors or bias
Usually come from the measuring instruments. Systematic
errors primarily influence a measurement's accuracy.
For example: Forgetting to zero or tare, a balance produces
false measurements
An error caused by not setting an instrument to zero prior to its
use is called an offset error.
Systematic error can occur due to - wrong with the instrument,
the instrument is wrongly used by the experimenter,
imperfect instrument calibration, and environmental
interference
Bias is a condition that causes a result to depart from the true
value
The principal biases are selection bias and measurement (or
classification) bias

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9. Confounding
Confounding is a independent variable that are not related to
purpose of study but may affect the dependent variable
❑ Special type of bias
❑ Affects the validity of a study
❑ It masks the true effect
❑ Persons who consume coffee are more likely to smoke than
people who do not drink coffee, and cigarette smoking is
known to be a cause of coronary heart disease.
Sajib Reza

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10. Sensitivity:
❑ The sensitivity of an index or indicator refers to the extent to
which it reflects nutritional status or predicts changes in
nutrition (genuinely malnourished)
❑ Sensitive indices (or indicators) show large changes as a
result of only small changes in nutritional status.
❑ An index (or indicator) with 100% sensitivity correctly
identifies all those individuals who are genuinely
malnourished: no malnourished persons are classified as
"well" (i.e., there are no false negatives).
❑ Sensitivity (Se) = true positives (TP) / [true positives (TP)+
false negatives (FN)]

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11. Specificity:
❑ The specificity of an index (or indicator) refers to the ability of the index (or indicator) to
identify and classify those persons who are genuinely well nourished.
❑ If an index (or indicator) has 100% specificity, all genuinely well-nourished individuals
will be correctly identified: no well-nourished individuals will be classified as "ill" (i.e.,
there are no false positives).
❑ Specificity (Sp) = True negatives (TN) / [True negatives (TN) + False positives (FP)]
❑ Factors modifying sensitivity and specificity:
• Cutoff points
• Extent of the random errors
• Non-nutritional factors – infection
• Biological and behavioral processes – neonate death due to LBW

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12. Prevalence
Prevalence refers to the total number of individuals in a
population who have a disease or health condition at a
specific period of time,
❑ Usually expressed as a percentage of the population.
❑ The number of persons with malnutrition or disease
during a given time period is measured by the prevalence
❑ Prevalence (P) = [True positives (TP)+ False negatives (FN)]
/ [True positives (TP) + False positives (FP) + True negatives
(TN) + False negatives (FN)]

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13. Predictive value
Defined as the likely-hood that a test correctly predicts the
presence or absence of malnutrition or disease
❑ Subdivided into the positive predictive value and the negative
predictive value.
❑The positive predictive value (v+) = True positives (TP) /
[True positives (TP) + False positives (FP)]
❑The negative predictive value (v-) = True negatives (TN) /
[True negatives (TN) + False negatives (FN)]
❑Predictive value (V) = [True positives (TP)+ True negatives
(TN)] / [True positives (TP) + False positives (FP) + True
negatives (TN) + False negatives (FN)]

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14. Ethical issues
❖Biomedical research are conduct according to the declaration of Helsinki by The World
Medical Association (WMA) (2008).
❖Ethical approval from the appropriate human ethics committees must be obtained by the
principal investigators before work begins.
❖Informed consent must be obtained from the participants or their principal caregivers
✓When securing informed consent, the investigator should also:
✓Disclose details of the nature and procedures of the study
✓Clearly state the associated potential risks and benefits
✓participation in the research is voluntary
✓participants are free to withdraw from the study at any time
✓Explain how the results relating to individual participants will be kept confidential
✓Describe the procedures that provide answers to any questions and further information
about the study.
Sajib Reza

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15. Additional factors:
▪ The acceptability of the method,
▪ Respondent burden,
▪ Equipment and personnel requirements,
▪ Field survey and data processing costs
▪ The methods should be acceptable to both the target population and the staff who
are performing the measurements.
▪ Example: collecting blood specimens in populations with a high prevalence of HIV
infections may be perceived to be an unacceptable risk by staff performing the tests.

38. Percentile
• Taking age and sex into consideration, differences in measurements can be
expressed in a number of ways such as standard deviation units (Z-scores),
percentage of the median or percentiles.
• Percentage of the median and percentiles: The percentage of the median is
defined as the ratio of a measured or observed value in the individual to the
median value of the reference data for the same age or height for the specific sex,
expressed as a percentage. This can be written in equation form as:
• Percent of median = (Observed value) x100 / Median value of reference
population
• If the child’s weight is 9.4 kg and the reference value is 11 kg, the percent of
median is = (9.4/11) x100 = 85 %
• The median is the value at exactly the midpoint between the largest and smallest.
• 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.

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Children’s BMI
Values are in percentile
< 5th percentile
5th - <85th percentile
85th - <95th percentile
≥ 95th percentile
BMI interpretation in
children
Underweight
Healthy
Overweight
Obese

40. Z-score
• The 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 for the
same age or height, divided by the standard deviation of the reference population.
This can be written in equation form as:
• Example: Assume, a 19 month old boy, who weighs 9.8 kilograms.
• Step-1: If we look at the reference standards for weight-for-age, we see that the
“average” healthy boy of 19 months weighs 11.7 kilograms.
• Step-2: Since this child is obviously under the mean of 11.7 kilograms, we need to
check the lower standard deviation value. It is 1.2 kilograms.
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• Step-3: Subtract the mean weight from the actual weight of the child. The results in
this case will be negative: 9.8 kg - 11.7 kg = -1.9
• Step-4: Divide the result by the standard deviation for the child’s age and gender.
In that case: -1.9/1.2 SD = -1.58 SD units.
• The resulting number is the Z-score for that child.
• The child is mild malnourished.
Sajib Reza

43. Thank you