Title: Non-Invasive Measurements Of Nutritional Status

Key words: Anthopometric measurements, body mass index (BMI), subjective global assessment (SGA),

Date: Oct 1998

Category: 14. Measurement

Type: Article

Author: Dr van Rhijn

Non-Invasive Measurements Of Nutritional Status

Introduction

In-depth assessments of an individual’s nutritional status include a detailed medical, social and dietary history as well as laboratory and biochemical tests. However, non-invasive methods are extremely valuable and will often suffice for this purpose.

• Height & Weight Present ideal body weight [%IBW = Actual BW x 100% / IBW]
• Mid-arm circumference (a measure of skeletal muscle mass)
• Skin-fold thickness (assesses subcutaneous fat stores)
• Body mass index (BMI) = weight (kg)/height (m)²
• Body density (underwater weighing)

It is difficult to measure skin-fold thickness in infants, and is therefore of little value. The WHO recommends that nutritional status is expressed as:

• % weight/height: a measure of wasting as an index of acute malnutrition
• % height/age: a measure of growth retardation as an index of chronic malnutrition
• Subjective Global Assessment (SGA)

This is a reproducible and practical technique to assess the risk of malnutrition.

It consists of:

• Weight change (loss in past 6 months in kg and in % loss)
• Dietary intake change (duration in weeks, gradation from none to starvation)
• Gastrointestinal symptoms (persisted > 2 weeks – nausea, vomiting, diarrhoea)
• Functional capacity (working, ambulatory, bedridden)
• Disease and its relation to nutritional requirements (none to high stress)
• Physical clinical examination

The SGA rating is a composite evaluation of the ability to eat, disease stress, functional impairment and clinical wasting. Although the physical examination is part of the SGA, it is generally invaluable in its own right for numerous clinical signs related to the nutritional status such as:

• Rickets; Pallor; Hair loss; Ulcers; Bruising; Bitot’s spots etc.

Non-invasive measurements have the benefit that they can be performed anywhere, without expensive laboratory backup. It only requires good clinical judgement and monitoring over time, which is probably the best available method for assessing nutritional status.