Assessing nutritional status in HIV positive adults

Summary of published research¹

Humanitarian agencies are starting antiretroviral (ARV) programmes in a number of conflict settings. Many of the patients in these programmes are malnourished and some require supplementary feeding in order to boost their nutritional status. However, the current means of measuring nutritional status of adults - body mass index (BMI) - may not be sensitive enough to take into account the physiology of HIV positive patients on ARVs (lean muscle wasting combined with lipodystrophy). Thus, while there is a depletion of lean body mass, weight itself may not change due to the extra fat being produced.

A variety of assessment tools can be used to determine nutritional status in both sick and healthy adults. These include anthropometric methods such as skinfold measurement and mid-upper-arm circumference (MUAC), subjective global assessment (SGA), BMI and more recently bioelectrical impedance analysis (BIA). The tool most commonly used to assess adults is BMI but this is insensitive to changes in lean muscle mass (LMM), which is a more accurate indicator of change in nutritional status. BIA is a technique developed to measure body composition, in particular, fat free mass, which leads to estimations of LMM. It has been used mainly in clinical and laboratory settings and has been validated for use in assessing body composition of HIV positive adults. The technology involves using electrical currents to measure resistance and reactance. SGA was originally developed to determine which patients need extra nutritional support following surgery for gastrointestinal problems and relies on a combination of patient history, clinical signs of malnutrition and assessment of muscle function using handgrip strength.

A recent review of the literature and a number of databases on all these measurement techniques was conducted to explore the optimal nutritional assessment methods for HIV positive adults. This review pointed out that all the methods examined have advantages and disadvantages in resource poor settings.

MUAC is a good tool for adult screening. It is lightweight, portable and easy to use and able to detect slight changes in skeletal muscle mass. However, there is likely to be a degree of operator error in the use and reading of the results.

Skinfold measurement is a good indicator of fat mass and changes in fat mass. However, it is unreliable in estimating fat free muscle or lean body mass.

SGA is a relatively new tool for HIV. It is less expensive than BIA and does not require mechanical equipment. Research so far suggests that it is a good tool for detecting early loss of muscle function indicating a loss of body cell mass.

BIA is a good tool for detecting body cell mass loss in HIVwasting and compares favourably with gold standard methods, e.g. measuring total body potassium and dual energy x-ray absorptiometry (DXA). The scales are relatively inexpensive (approximately £700) and easily portable. However, certain conditions must exist for measurements. For example, subjects must be well hydrated and not exercised for 24-48 hours before measurement. This may make it a poor tool for screening in an African clinic where most patients have to travel long distances in high temperatures to reach a clinic.

The study concluded that for all the tools examined, the prediction equations have been formulated on the basis of data gathered from western populations and there is need for more research based on African populations. BIA is not a good tool for screening for wasting, but would be a good tool for monitoring changing nutritional status in in-patients. A combination of BMI and MUAC are good tools for measuring the nutritional status of HIV positive adults in an outpatient setting.

For further information contact: Sarah Kelly, email: sarah.kelly@paediatrics.ox.ac.uk

¹Kelly. S (2006). Bio-electrical Impedance Analysis. A tool for screening. MSc Public Health in Developing Country Project Report. August 2006.