Nutritional Status Assessment in Adults

Background

An assessment of nutritional status in adults may include a comprehensive evaluation consisting of a tailored history and physical examination, laboratory assessment, anthropometrics, body composition, and functional data. 

No single variable accurately and reliably relays nutritional status of a subject in every situation. Validated screening tools are available for use in certain populations.

Poor nutritional status has been known to have unfavorable effects. Individuals with less than 80% expected total body protein levels have demonstrated increased morbidity, and 10% or greater unintentional weight loss has been associated with adverse outcomes and prolonged hospitalizations. In lean healthy subjects, weight loss over 35%, protein loss over 30%, and fat loss over 70% from baseline has been associated with death. [3]

Indications

Measurement of nutritional status in adults has no absolute indications. The importance of nutritional assessment becomes apparent during acute illness, in which malnutrition has been associated with increased morbidity and mortality. Identification of malnourishment and appropriate intervention may improve outcomes.

Contraindications

Assessment of nutritional status in adults has no specific contraindications. However, owing to the cooperation required, hydrodensitometry may not be suitable for subjects who are physically challenged, children, or elderly persons. Additionally, bioelectrical impedance analysis (BIA) should not be performed in subjects with pacemakers.


Equipment

Height is measured with a stadiometer (see image below).

Stadiometer. Courtesy of the Scottish Health SurveStadiometer. Courtesy of the Scottish Health Survey 2010 - Volume 2: Technical Report published by the Scottish Government, available at http://www.scotland.gov.uk/Publications/2011/09/27124046/0.

Weight is measured with a scale (see image below).

Scale. Courtesy of Detecto Scale (www.Detecto.com)Scale. Courtesy of Detecto Scale (www.Detecto.com).

The images below show various tools used for body composition analysis.

Metal Harpenden calipers. Courtesy of Baty InternaMetal Harpenden calipers. Courtesy of Baty International Ltd.
Plastic calipers. Courtesy of Wikipedia. Plastic calipers. Courtesy of Wikipedia.
DEXA scanner. Courtesy of CDC. DEXA scanner. Courtesy of CDC.
Hydrodensitometer. Courtesy of Human Performance LHydrodensitometer. Courtesy of Human Performance Lab, University of Wisconsin-La Crosse.
Air displacement plethysmograph. Courtesy of WikipAir displacement plethysmograph. Courtesy of Wikipedia.
Fist-grip (hand) dynamometer. Courtesy of LafayettFist-grip (hand) dynamometer. Courtesy of Lafayette Instrument Company, Inc.

Monitoring & Follow-up

No long-term monitoring or follow-up is needed after nutritional status assessment in adults. However, serial assessments prove useful in monitoring nutritional status and responses to intervention over time.

History and Physical Examination

Comprehensive nutritional assessment begins with a history and physical examination. History should consist of medical diagnoses, hospitalizations, changes in appetite, availability and preparation of food, medications, and details regarding weight change. Weight loss is perhaps the most validated parameter of nutritional status. [4]

Following the history, a thorough physical examination may be performed. Attention should be directed toward findings of soft-tissue wasting, hydration status, evidence of vitamin and mineral deficiencies, height, weight, and body mass index (BMI). See Table 1 for a description of physical examination findings and related nutrient deficiencies.

Table 1. Symptoms and Signs of Nutritional Deficiency (from the Merck Manual of Diagnosis and Therapy, edited by Robert Porter. Copyright 2012 by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co, Inc, Whitehouse Station, NJ. Available at http://www.merckmanuals.com/professional/. Accessed 11/18/2013) (Open Table in a new window)

Area/System

Symptom or Sign

Deficiency

General appearance

Wasting

Energy

Skin

Rash

Many vitamins, zinc, essential fatty acids

Rash in sun-exposed areas

Niacin (pellagra)

Easy bruising

Vitamin C or K

Hair and nails

Thinning or loss of hair

Protein

Premature whitening of hair

Selenium

Spooning (upcurling) of nails

Iron

Eyes

Impaired night vision

Vitamin A

Corneal keratomalacia (corneal drying and clouding)

Vitamin A

Mouth

Cheilosis and glossitis

Riboflavin, niacin, pyridoxine, iron

Bleeding gums

Vitamin C, riboflavin

Extremities

Edema

Protein

Neurologic

Paresthesias or numbness in a stocking-glove distribution

Thiamin (beriberi)

Tetany

Ca, Mg

Cognitive and sensory deficits

Thiamin, niacin, pyridoxine, vitamin B12

Dementia

Thiamin, niacin, vitamin B12

Musculoskeletal

Wasting of muscle

Protein

Bone deformities (e.g., bowlegs, knocked knees, curved spine)

Vitamin D, Ca

Bone tenderness

Vitamin D

Joint pain or swelling

Vitamin C

GI

Diarrhea

Protein, niacin, folate, vitamin B12

Diarrhea and dysgeusia

Zinc

Dysphagia or odynophagia (due to Plummer-Vinson syndrome)

Iron

Endocrine

Thyromegaly

Iodine

Anthropometric Measures

Procedural videos for performance of a variety of anthropometric measures can be found at http://www.cdc.gov/nchs/nhanes/nhanes3/anthropometric_videos.htm.

Height, weight, and body mass index

Height should ideally be measured with a stadiometer. However, it is possible to estimate height by arm span or knee-height measurement in some subjects who are unable to stand. [4]

Perform weight measurement with the subject standing, shoes and overgarments removed. Serial weight measurements to assess trends of weight gain or loss are particularly useful in providing objective insight into changes over time. Sustained weight loss from baseline (over 6 months) can be categorized into mild (< 5%), moderate (5%-10%), or severe (>10%). Severe weight loss has been associated with impaired physiology, poor outcomes, and prolonged hospitalization. [3]

Weight is proportional to height, and this relationship, known as the BMI, is one of the most commonly used and simplest anthropometric measures. [5The proposed categories of BMI by the National Institutes of Health include underweight (< 18.5), desirable (18.5-24.9), overweight (25-29.9), and obese (≥30). [4BMI is calculated with the following equations:

BMI = weight (kg)/height2 (m2)

BMI = (weight [lb] X 703)/height2 (in2)

The graph below can also be used for determination of BMI and its categories.

BMI graph. Courtesy of Wikipedia. BMI graph. Courtesy of Wikipedia.

Skinfold thickness

Skinfold thickness is an indirect measure of subcutaneous adipose tissue using skinfold calipers at various body sites. Body density and percentage body fat can then be estimated based on these measurements.

Commonly used equations for body density estimation are those of Durnin and Womersley [6and Jackson and Pollock [7. Percentage body fat can be estimated with the equations of Siri [8or Brozek et al [9. The accuracy of skinfold thickness is highly operator-dependent, declines with the use of plastic calipers compared with Harpenden or Lange metal calipers, [10and declines with increasing obesity. [11]

Details of skinfold sites, procedures for measuring skinfold thickness, and equations for body density and body fat percentage are listed below.

Standardized description of skinfold sites and procedures [12]

Skinfold sites include the following:

  • Triceps: Vertical fold on the posterior midline of the upper arm, halfway between the acromion and olecranon processes, with the arm held freely to the side of the body

  • Chest/Pectoral: Diagonal fold, one half the distance between the anterior axillary line and the nipple (in men) or one‐third of the distance between the anterior axillary line and the nipple (in women)

  • Subscapular: Diagonal fold (at a 45° angle), 1-2 cm below the inferior angle of the scapula

  • Abdomen: Vertical fold, 2 cm to the right of the umbilicus

  • Suprailiac: Diagonal fold in line with the natural angle of the iliac crest taken in the anterior axillary line immediately superior to the iliac crest

  • Thigh: Vertical fold on the anterior midline of the thigh, midway between the proximal border of the patella the inguinal crease (hip)

Procedures include the following:

  • Perform measurements on the right side of the body

  • Place caliper 1 cm from the thumb and finger (pinch), perpendicular to the skinfold, halfway between the crest and base of the fold

  • Maintain pinch while reading the caliper

  • Wait no longer than 1-2 seconds before reading the caliper

  • Retest measurements if they are not within 1-2 mm, allowing sufficient time between measurements for skin to regain normal texture and thickness

Equations for estimation of body density [13]

The most commonly used equations for estimation of body density in men and women are based on the 3-site formula of Jackson and Pollock, as follows:

Females: Body density = 1.0994921 - 0.0009929(sum of 3 skinfolds) + 0.0000023(sum of 3 skinfolds)2 - 0.0001392(age). From triceps, suprailiac, thigh skinfold measurements.

Males: Body density = 1.1093800 - 0.0008267(sum of 3 skinfolds) + 0.0000016(sum of 3 skinfolds)2 - 0.0002574(age). From chest, abdominal, thigh skinfold measurements.

Equations for conversion of body density to percent body fat [89]

The two most commonly used equations for estimation of body fat from body density are those of Siri and Brozek, as follows:

Siri equation: Percentage body fat = (495/body density) - 450

Brozek equation: Percentage fat = (457/body density) - 414.2

The image below depicts triceps skinfold thickness measurement with plastic calipers.

Tricep skinfold thickness measurement with plasticTricep skinfold thickness measurement with plastic calipers. Courtesy of the CDC.

The image below depicts subscapular skinfold thickness measurement with plastic calipers.

Subscapular skinfold thickness measurement with plSubscapular skinfold thickness measurement with plastic calipers. Courtesy of the CDC.

Mid-arm muscle circumference and mid-upper-arm muscle area

Mid-arm muscle circumference (MAMC) has been used for reflection of muscle protein reserves. [14This is performed in addition to triceps skinfold measurement to calculate mid-upper-arm muscle area, which correlates with lean body mass. These anthropometric measures have proven easy to perform and correlate with mortality in older adults and in patients with cirrhosis. [31516]

Obtaining the MAMC requires that the upper-arm length first be measured and the halfway point determined, marking this location for measuring circumference. The subject should stand with weight distributed evenly on both feet and right arm bent 90°. Arm length is measured from the most superior point on the scapular spine to the tip of the olecranon process on the posterior aspect of the arm (see image below).

Upper arm length measurement and mid-arm mark. CouUpper arm length measurement and mid-arm mark. Courtesy of the CDC.

Circumference measurement is performed with a measuring tape positioned perpendicular to the length of the arm, at the marked location. Triceps skinfold should be performed at this location also.

Once arm circumference and skinfold measurements are complete, the results can be used to calculate mid-upper-arm muscle area using the equations below. Standards for upper-arm muscle area can be found in Table 2, based on National Health and Nutrition Examination Survey (NHANES) data.

The following equations are used for mid-upper arm muscle area:

Men (cm2): Area = ([arm circumference – {∏ x triceps skinfold}]2/4∏) - 10

Women (cm2): Area = ([arm circumference – {∏ x triceps skinfold}]2/4∏) - 6.5

Table 2: Standards for Upper Arm Muscle Area in Adults (From the Merck Manual of Diagnosis and Therapy, edited by Robert Porter. Copyright 2012 by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co, Inc, Whitehouse Station, NJ. Available at http://www.merckmanuals.com/professional/. Accessed 11/18/2013). (Open Table in a new window)

Percentage of Standard (%)

Men (cm2)

Women (cm2)

Muscle Mass

100 ± 20*

54 ± 11

30 ± 7

Adequate

75

40

22

Marginal

60

32

18

Depleted

50

27

15

Wasted

*Mean mid upper arm muscle mass ± 1 standard deviation. From the National Health and Nutrition Examination Surveys I and II.

Nutrition Screening

There are few validated screening tools for assessment of nutritional status. Perhaps the most studied are the subjective global assessment of nutrition (SGA) and mini-nutritional assessment (MNA).

Subjective global assessment

The SGA, first described in 1982, is a screening tool that categorizes nutritional status into 3 designations: "well nourished" (grade A), "suspected malnutrition/moderately malnourished" (grade B), and "severely malnourished" (grade C). This tool considers history, physical examination, and functional capacity and has been used in most patient populations. It has been studied most widely in surgical patients. [17An example form is below.

Subjective Global Assessment (SGA) form. Subjective Global Assessment (SGA) form.

Obtain history pertaining to weight change, dietary intake, gastrointestinal symptoms, functional capacity, and medical conditions. The physical examination is tailored toward signs of malnutrition, including loss of subcutaneous fat, muscle-wasting, edema, and ascites, with severity graded from “none” to “severe.” The clinician then subjectively designates the overall nutritional status of the patient into one of 3 categories: "well nourished" (grade A), “mild-moderate malnutrition" (grade B), or "severe malnutrition" (grade C).

Mini-nutritional assessment

The MNA was developed in 1989 to assess nutritional status among elderly patients (>65 years) in clinical practice. [18Two forms are available, the full and short MNA. The full assessment is divided into 4 groups: anthropometrics, general assessment, dietary assessment, and subjective assessment. Answers are assigned numerical values, which are added to a maximum score of 30. Nutritional status is divided into 3 groups: "well-nourished" (score ≥24), "at risk for malnutrition" (17-23.9), and "malnourished" (< 17).

The short-form mini-nutritional assessment (MNA-SF), initially used in low-risk community-dwelling elderly populations, is now the preferred form of MNA for all elderly patients. Performed in two steps, the first step (screening) consists of 6 items strongly correlated with results from the full MNA and categorizes nutritional status as above. The second step is a further assessment of those “at risk for malnutrition” or “malnourished” by screening. The MNA-SF screening score reaches a maximum of 14.

Scores of 12 or more indicate satisfactory nutrition, and no further assessment is necessary. Scores of 8-11 suggest “risk for malnutrition,” and scores of 0-7 suggest a “malnourished” subject; with these designations, the full MNA is indicated.

Further information on the MNA can be found at www.mna-elderly.com. Examples of both the short (MNA-SF) [19and full form of MNA [19are below.

MNA®-Short Form. Courtesy of Nestlé Nutrition InstMNA®-Short Form. Courtesy of Nestlé Nutrition Institute (http://www.mna-elderly.com/).
MNA®-Long Form. Courtesy of Nestlé Nutrition InstiMNA®-Long Form. Courtesy of Nestlé Nutrition Institute (http://www.mna-elderly.com/).

Advanced Body Composition Analysis

Advanced studies for body composition assessment include dual-energy X-ray absorptiometry (DEXA), underwater (hydrostatic) weighing, air displacement plethysmography (ADP), and bioelectrical impedance analysis (BIA).

Dual-energy X-ray absorptiometry

DEXA is considered by many to be the criterion standard for assessment of percentage of body fat but has been shown to overestimate in those with a high fat percentage and to underestimate in those with low fat percentage. [5Its primary application has been in the assessment of bone mineral density. Whole-body scans can be used to directly measure fat and lean mass through x-ray attenuation. [20Radiation exposure from a single whole-body DEXA scan ranges from 0.04-0.86 millirem, or roughly 1%-10% that of chest radiography. [21]

Subject preparation should begin with removal of all items from shirt and pants pockets. Subjects should lie supine on the scanner, their body in the center of the table within the scan-lines. The head should be tilted just slightly back and arms placed flat to each side of the body, with fingers together. No part of the body should be overlapping. Once positioning is confirmed, the scan can begin. The subject should remain still until the scan is complete, indicated by the scan arm moving to the home position. The machine then estimates body composition in 3 compartments (fat mass, fat-free mass, and bone mineral).

For obese subjects who do not completely fit on the scanner table, a hemi-scan protocol may be used. For this method, the subject lies on his or her right side, with left-sided body parts that do not fit on the scanner excluded by placement over the left side of the table. Any left-sided body parts that are excluded can be estimated by doubling of right-sided data.

Underwater (hydrostatic) weighing

Hydrodensitometry, also known as hydrostatic or underwater weighing, was the criterion standard two-compartment (fat and fat-free mass) model of body composition before DEXA.

This method relies on the Archimedes principle to determine total body volume through difference in body weight in air and underwater. [22It is hindered by requiring significant subject cooperation and may not be appropriate in subjects who are physically challenged, children, or elderly. [23Once weight and volume are measured, body density can be estimated based on the equation below.

Body density = Wa ÷ {[(Wa – Ws) ÷ Dw] – (Vr + 0.1)}

(Wa = weight in air [kg]; Ws = weight submerged [kg]; Dw = density of water, with allowances being made for residual gas volume in the lungs [Vr] and GI gas [0.1L])

Percentage body fat is estimated by the previously described equations of Siri and Brozek. [8924Changes in hydration status, pre-assessment nutrition, and exercise can significantly affect results.

Air displacement plethysmography

ADP uses methods similar to those of hydrostatic weighing for measurement of two-compartment body composition. The inverse relationship between volume and pressure (Boyle's law), is applied for body volume determination. [20Body density is then estimated and composition calculated with either the Siri or Brozek equation. [8922This method has been shown to be as reliable as hydrostatic weighing and DEXA. [5]

ADP requires that the subject first change into a swimsuit and wear a swim-cap to reduce the isothermal effect of clothing and hair that might cause underestimation of body volume. Subjects should void both the bladder and bowels prior to testing. Height and weight should be measured by the clinician to the nearest centimeter and 5 grams, respectively, using the ADP’s scales.

Prior to placing the subject into the chamber, a two-point calibration should be performed with the chamber empty, then with a 50-liter calibration cylinder. Once calibration is complete, the subject may enter the chamber and the door can be closed. The subject remains still while body volume is measured. This should be performed at least twice or until 2 results agree to within 150 mL. The subject should then be connected to the ADP’s breathing circuit to assess thoracic gas (lung) volume.

From these measures, body density is determined and percentage body fat estimated. [23]

Bioelectrical impedance analysis

Also based on a two-compartment model is BIA, which is used to measure resistance/impedance of a small electrical current as it passes through the body’s water pool. [21Resistance to current flow is greater through adipose tissue and bone mineral than fat-free mass, as its water content is low. [10Total body water is estimated and fat-free mass calculated based on the assumption that 73% of the body’s fat-free mass is water. [5This method is easily performed, portable, noninvasive, and more affordable than other methods. It is generally safe, although it is not recommended in subjects with pacemakers.

The testing procedure for BIA varies depending on the device used. In general, the subject should abstain from exercise or sauna within 8 hours of the procedure and alcohol intake within 12 hours of procedure. Wet skin, as in diaphoretic or incontinent subjects, interferes with test results. Path of current flow depends on the device used and location of electrodes. Electrode sites should be cleaned with an alcohol wipe, particularly if the skin is moist or covered with lotion. Once electrodes are in place, the analyzer can be turned on and resistance and reactance recorded. From these measures, body-fat mass and fat-free mass can be estimated.

Functional Measure of Nutrition Status: Fist-Grip Dynamometry

The most validated functional measure of nutritional status is fist-grip dynamometry (FGD). This technique is based on the impairment in muscle function that occurs in malnourished subjects. A handheld dynamometer is used to measure maximal hand-grip force, which correlates well with total body protein. [3In surgical patients, fist-grip strength 85% or less than age- and sex-corrected standards is associated with twice the risk of perioperative complications. The American Society for Surgery of the Hand (ASSH) and American Society of Hand Therapists (ASHT) have standardized techniques for its performance. [19]

The reliability of this measure depends on factors such as wrist and forearm position, degree of elbow flexion, posture, shoulder position, time of day, interval between measurements, and amount of encouragement offered. According to the protocol of the American Society of Hand Therapists (ASHT), the fist-grip dynamometer should be used with the subject in the seated position, shoulders adducted and neutrally rotated, elbow flexed at 90° with the forearm and wrist in a neutral position.

Ideally, the dynamometer used should have an adjustable handle to accommodate different hand sizes. The subject should squeeze the dynamometer with as much force as possible.

According to the Southampton protocol, 3 trials should be performed on both the dominant and nondominant hands and the best of the 6 measurements used for comparison with age- and sex-adjusted standards. 

Laboratory Medicine Summary

Serum proteins (albumin, transferrin, prealbumin, retinol-binding protein) are perhaps the most widely used laboratory measures of nutritional status. They are hepatically produced negative acute-phase reactants with reduced levels during systemic inflammation. However, in the absence of inflammation, a low concentration of these proteins correlates strongly with malnutrition. [3Details of these proteins can be found in Table 3.

Table 3: Serum Proteins Used for Assessment of Nutritional Status [32627(Open Table in a new window)

Protein

Half-life, days

Function

Comment

Albumin

14-20

Maintenance of plasma oncotic pressure; carrier protein

levels increase with dehydration, blood and albumin transfusion, and anabolic steroids

levels decrease in liver failure, inflammation, volume overload states (cirrhosis, congestive heart failure, renal failure), zinc deficiency, protein-losing states (nephrotic syndrome, enteropathy), corticosteroid use, and bedrest

Transferrin

8-9

Iron transport

levels increase during dehydration, iron deficiency, pregnancy, estrogen therapy, and acute hepatitis

levels decrease in liver and renal failure, inflammation, anemia due to chronic disease and vitamin B12 and folate deficiency, corticosteroids, zinc deficiency, and protein-losing states (nephrotic syndrome, enteropathy)

Often measured indirectly as total iron-binding capacity (TIBC)

Prealbumin (transthyretin)

2-3

Binds thyroxine; carrier for retinol-binding protein

levels increase in renal failure (degraded by the kidney) and corticosteroid and oral contraceptive use

levels decrease in liver failure, inflammation, and hyperthyroidism

Retinol-binding protein (RBP)

12-24

Vitamin A transport; binds to prealbumin

levels increase in renal failure (degraded by the kidney)

levels decrease in cirrhosis, inflammation, vitamin A and zinc deficiency, and hyperthyroidism