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close this bookMethods for the Evaluation of the Impact of Food and Nutrition Programmes (UNU, 1984, 287 p.)
close this folder4. Measuring impact using laboratory methodologies
View the document(introduction...)
View the documentIntroduction
View the documentDevelopment of a primary nutritional deficiency
View the documentChoice of tissue for laboratory assessment
View the documentSelection of laboratory methodologies for nutritional impact evaluation
View the documentLaboratory methods for assessment of nutritional impact
View the documentAnnex A. Laboratory evaluation of protein nutriture
View the documentAnnex B. Laboratory evaluation of vitamin A nutriture
View the documentAnnex C. Suggested methods for hematology
View the documentReferences

Selection of laboratory methodologies for nutritional impact evaluation

The appropriateness of using laboratory measurement for nutritional impact evaluation will depend on the nature of the intervention programme and the kind, severity, and prevalence of nutritional problems in the recipient population (see TABLE 4.1. Summary of Laboratory Methodology (Nutritional Biochemistry and Hematology)). Laboratory measurements are most appropriately applied in tandem with the introduction of specific, population-based nutrient interventions, such as iron, iodine, or vitamin A food fortification programmes, or in interventions targeted to individuals who are given specific supplements for which specific before-and after-treatment effects can be measured.

TABLE 4.1. Summary of Laboratory Methodology (Nutritional Biochemistry and Hematology)

Kind of Information Kind of Intervention Unit of Observation Personnel
Training
Resources Required Time Level Survey
Albumin/ Prealbumin Protein-calorie supplement to malnourished vulnerable groups Individual Lab. tech. (2 weeks) Radio-immuno diffusion kit, refrigeration 10-30
samples/day
Minimal
Prevalence of low serum retinol levels Vitamin A Individual (1 month) Lab. tech. HPLC Spectrophotometric
Colorimetric
20 specs./day Sophisticated Appropriate for LDCs
Hemoglobin concentration or hematocrit Iron Individual Lab. tech. (2 weeks) Colorimetric 3 minutes Minimum for difficult field conditions
Transferrin saturation Iron Individual Lab. tech. (1 month) Spectrophotometer 20 minutes Sophisticated
Free erythrocyte Iron Individual Lab. tech.

(1 week)

Hematofluorometer 3 minutes Simple
Protoporphyrin     Lab. tech. (1 month) Fluorometer or Spectrophotometer 20 minutes  
Serum ferritin Iron Individual Lab. tech. (1 month) Refrigerator Centrifuge Gamma counter or Spectrophotometer Serum ferritin kit 20 minutes Sophisticated

 

Biochemical measurements are also appropriate where intervention programmes, even non-nutrient-specific ones, are clearly targeted to vulnerable population groups with known significant dietary inadequacies. One example would be preschool children from poor environments in which PEM is prevalent and among their pregnant and lactating mothers.

Biochemical methods may not be useful in evaluating general food aid programmes for adult workers with only marginally adequate diets. Under these circumstances, limitations in the magnitude of biochemical responsiveness to moderate dietary change that can be reliably detected by laboratory measurements could preclude usefulness. For example, clearly it would be inappropriate to apply laboratory assessment of iron and vitamin A status to evaluate a food aid programme such as a grain distribution in a food-for-work programme, that did not include significant amount of these nutrients. Furthermore. it is unlikely that significant alterations in protein status would be detected by laboratory methodology in this type of adult recipient population.

In contrast, however, a feeding programme including a protein ration for preschool, poor children is likely to show a shift upward in the distribution of albumin levels from the lower range of the distribution curve. Because laboratory measurements are costly with respect to employment of professional personnel and possible continued cooperation of programme recipients, the decision of evaluators to include laboratory assessment should be carefully matched to the specific programme being evaluated, to maximize the potential for obtaining interpretable data on nutritional impact.