Nutritional Assessment Systems

• Nutritional assessment systems


  • Nutrition Survey
  • Nutrition Surveillance
  • Nutrition Screening
  • Assessment of nutrition interventions
  • Assessment in clinical settings
• Each of the systems utilizes a variety of nutritional assessment methods either alone or more effectively in combination (depending on the study objectives and available resources)
• Population or community nutrition assessment


  The nutritional situation of a community is the sum of the nutritional status of all members of the community
• In a survey, only a representative group of persons may be examined
• At the individual level, screening can be initially carried out to identify the probable nutritional problem of a frail elderly, followed by a more comprehensive baseline nutritional assessment for better nutritional diagnosis in order to establish the nature and severity of malnutrition
• Nutrition survey


  Also referred to as cross-sectional survey, national nutrition surveys
• Objectives of nutrition surveys

  • Establish baseline nutritional data
  • Ascertain the overall nutritional status of the population
• Uses of cross-sectional nutrition surveys


  Examine associations, and to identify and describe population subgroups "at risk" for chronic malnutrition
• Causal relationships cannot be established from cross-sectional surveys because whether the exposure precedes or follows the effect is unknown, and they are also unlikely to identify acute malnutrition because all the measurements are taken on a single occasion or within a short time period with no follow-up
• Strengths of cross-sectional nutrition surveys

  • Obtain information on prevalence, defined as the proportion who have a condition or disease at one time point for use by health planners
  • Cross-sectional surveys are a necessary and frequent first step in subsequent investigations into the causes of malnutrition or disease
• Nutrition surveillance


  Continuous monitoring of the nutritional status of selected population groups
• Surveillance studies differ from nutrition surveys because the data are collected, analyzed, and utilized over an extended period of time, and can identify the possible causes of both chronic and acute malnutrition and, hence, can be used to formulate and initiate intervention measures at either the population or the subpopulation level
• Objectives of nutrition surveillance

  • Aid long-term planning in health and development
  • Provide input for program management and evaluation
  • Give timely warning of the need for intervention to prevent critical deteriorations in food consumption
• Nutrition screening


  The identification of malnourished individuals requiring intervention
• Nutrition screening involves a comparison of measurements on individuals with predetermined risk levels or "cutoff" points using measurements that are accurate, simple and cheap, and which can be applied rapidly on a large scale
• Types of nutrition screening tools

  • Subjective Global assessment (SGA)
  • Malnutrition Universal Screening Tool (MUST)
  • Mid-upper-arm circumference (MUAC) to diagnose SAM in children aged 6–60mos
  • Screening to identify individuals who might benefit from the Supplemental Nutrition Assistance Program in the United States
• Nutrition interventions


  Often target population subgroups identified as "at-risk" during nutrition surveys or by nutrition screening
• Types of evaluation for nutrition interventions

  • Adequacy evaluation
  • Plausibility evaluation
  • Probability evaluation
• Adequacy evaluation


  Achieved when it has not been feasible to include a comparison or control group in the intervention design; instead, a within-group design has been used
• Plausibility evaluation


  Can be conducted with several designs, including a nonrandomized between-group design, termed a quasi-experimental design in which the experimental group receives the intervention, but the control group does not
• Probability evaluation


  Provides the highest level of evidence that the intervention caused the outcome, and is considered the gold standard method, requiring the use of a randomized, controlled, double-blind experimental design, in which the participants are randomly assigned to either the intervention or the control group
• Figure 1.1 illustrates the importance of the participants being randomized to either the intervention or the control group when the control group outcomes have also improved as a result of nonprogram factors
• The types of nutritional assessment systems used in the community have been adopted in clinical medicine to assess the nutritional status of hospitalized patients
• Personalized nutrition is a rapidly expanding approach that is being used in a clinical setting, tailoring dietary recommendations to the specific biological requirements of an individual on the basis of their health status and performance goals
• Factors in the design of nutritional assessment systems

  • Study objectives
  • Ethical issues
  • Choosing the study participants and sampling protocol
  • Calculating the sample size
  • Collecting the data
  • Additional considerations
• Study objectives


  The design of the nutritional assessment system should be dictated by the study objectives, which can either be at the population or individual levels
• Examples of study objectives

  • Nutrition survey: To determine overall nutritional status of a population or sub-population, to identify areas, populations, or sub-populations at risk of chronic malnutrition, to characterize the extent and nature of malnutrition within the population or sub-population
  • Nutrition surveillance: To identify possible causes of malnutrition with the population or sub-population, to establish basis for designing appropriate intervention for high-risk populations or sub-populations (can also be achieved through Nutrition screening)
  • Nutrition screening: To monitor progress of changing nutritional, health, or socioeconomic influences, including intervention programs, to evaluate the efficacy and effectiveness of intervention programs, to track progress toward the attainment of long-range goals
• Ethical issues


  • Declare risks to subjects
  • Monitor data to ensure safety of subjects
  • Equitable selection of subjects
  • Provide additional safeguards for vulnerable subjects
  • Obtain informed consent
  • Ensure confidentiality
• Defining a set of inclusion/exclusion criteria and selecting a sample representative of the target population and of a size adequate for achieving the primary study objectives, requires the assistance of a statistician
• Sampling protocol and sample size


  Factors influencing the choice of sampling protocol is the availability of sampling frame, sample size, time, resources, and logistical constraints
• Different types of sampling protocols

  • Probability: Simple random sampling, Stratified random sampling, Multistage random sampling
  • Nonprobability: Consecutive sampling, Purposive sampling, Snowball sampling
• Every effort must be made to minimize the number of nonrespondents so that the generalizability (i.e., external validity) of the study is not compromised
• Nonprobability sampling methods


  • Consecutive sampling
  • Convenience sampling
  • Quota sampling
• Probability sampling methods


  • Simple random sampling
  • Stratified random sampling
  • Multistage random sampling
• Probability sampling


  • Every sampling unit (often the individual) has an equal probability of being sampled
• The level of nonresponse that will compromise the generalizability of the study depends on the nature of the research question and on the reasons for not responding
• Consecutive sampling


  Recruit all available patients who meet the criteria over a period of time
• Convenience sampling


  Consenting individuals who are available at the time of data collection. This approach is used when the population to be sampled is relatively homogeneous.
• Quota sampling


  Different categories and taking a certain number of consenting individuals
• Calculating sample size


  1. Restate research hypothesis to one that proposes no difference between the groups

  2. Select a reasonable effect size and variability

  3. Set α and β

  4. Select appropriate procedure for estimating sample size