1. Assessment of Protein Status
FCSN Nutrition Assessment Laboratory
Dr. David L. Gee
Central Washington University

2. Assessment of Protein Status
Anthropometric Assessment
body composition estimations
midarm muscle circumference/area
Laboratory Assessment
serum albumin
other serum proteins (transferrin, prealbumin, retinol-binding protein)
urinary creatinine excretion
total lymphocyte count

3. Midarm Muscle Area
Estimate of MAMA is an estimate of overall muscle mass
single point vs serial measurements
Assumptions
arm, muscle, bone are circular
TSF is 2X the thickness of fat
bone area is constant

4. Midarm Muscle Circumference
MAMC = AC - (.314 x TSF)
MAMC = midarm muscle circumference in cm
AC = arm circumference in cm
TSF = tricep skinfold in mm
“…change in arm muscle area is greater than the change in mid-arm circumference. Consequently, changes in upper-arm musculature are not as easily detected by measurement of mid-arm circumference as by AMA. Therefore, AMA is the preferred nutritional index.”

5. Arm Muscle Area AMA = ((MAC - (3.14 x TSF)2 ) / (4 x 3.14)
AMA = arm muscle area (cm2)
MAC = mid-arm circumference (cm)
TSF = tricep skinfold thickness (cm)
Or units of AMA, MAC, TSF all in mm
To convert mm2 to cm2, divide mm2/100
adjusted AMA
corrected for “bone free” AMA
Subtract constant from AMA to account for bone, nervous tissue, vascular tissue.
p-304

7. Percentile Category < 5th pct Wasted 5th -15th pct Below Average
Table 7.6 Guidelines for Interpreting Percentile Values for Arm Muscle Area (appendix R)
Percentile
Category
< 5th pct
Wasted
5th -15th pct
Below Average
15th - 85th pct
Average
85th – 95th pct
Above Average
> 95th pct
High Muscle

8. Biochemical Assessment of Protein Status
Two protein compartment model
Somatic protein (skeletal muscle protein)
~75% of total body protein
Visceral protein (internal organs, blood cells, serum proteins)
~ 25% of total body protein
“No single test or group of tests can be recommended at this time as a routine and reliable indicator of protein status.” Young, 1990
“…a combination of measures can produce a more complete picture of protein status.”
Biochemical, anthropometric, dietary, and clinical findings

9. Serum Albumin Major serum protein
Synthesized in liver
Maintains serum osmolarity
Serum carrier of small molecues
Most common indicator of depleted protein status 5

10. Serum Albumin Half life = 14-20 days
large body pool
poor indicator of early protein depletion and repletion
Levels affected by rate of synthesis (liver disease may reduce levels)
May reflect level of physiological stress
Decreased during acute catabolic phase 6

11. Serum Albumin Levels affected by abnormal losses
thermal burns – losses at burn site
nephrotic syndrome – losses in urine
protein-losing enteropathies – losses in feces
Levels affected by fluid status
congestive heart disease & fluid overload
Reduced due to dilution
Dehydration
Increased due to concentration effects
Normal values: 4.5 g/dL (SD) 7

12. Serum Transferrin Function: transport protein for iron
half-life = 8-9 days
better index of changes of protein status
Influenced by other factors
Increased with iron deficiency
increased during pregnancy, estrogen therapy
reduced in protein-losing enteropathy, nephropathy, acute catabolic stress
limited usefulness in protein status assess.

13. Serum Prealbumin aka. transthyretin and thyroxine-binding prealbumin
functions:
transport protein for thyroxine
carrier protein for retinol binding protein
short half life (2-3d), small body pool
sensitive indicator of protein status
responds more rapidly than albumin or transferrin

14. Serum Prealbumin Returns to normal at beginning of nutritional therapy
therefore do not use as endpoint for terminating nutritional therapy
Influenced by other factors
increased in chronic renal failure on dialysis
reduced in acute catabolic states, post surgery, tissue trauma, sepsis
generally considered preferable than albumin and transferrin

15. Retinol Binding Protein
Function: carrier for retinol
complexes with prealbumin (1:1)
responds like prealbumin
very rapid turnover (12 hours), very small body pool
may be too sensitive and complicates precise measurements
generally not considered to be more useful than prealbumin

16. Immunocompetence Immune system affected by nutritional status
Tests of immunocompetence useful functional indicators of nutritional status
Delayed Cutaneous Hypersensitivty (DCH)
intradermal injection of antigens
Total Lymphocyte Count (TLC)

17. Total Lympocyte Count White blood cell count TLC = (%lymp x WBC)x100
elevated with infections
used with % lymphocyte to get total lymphocyte count (TLC)
TLC = (%lymp x WBC)x100
ex: TLC=(37.2%x4100)x100 =1525 cells/mm3

18. Total Lympocyte Count
Normal = cells/mm3
Moderate PCM =
Severe PCM = < 800

19. Urinary Creatinine Excretion
Creatinine excreted in proportion to muscle mass
LBM estimated by comparing 24-hr urine creatinine excretion with standard based on stature or reference values of 23 and 18 mg/kg for M and F

20. Example:
Joe is 5’10” tall, 178cm
70kg
24hr creatinine excretion =
1436 mg
Expected
= 23 x 70 = 1610 mg
% expected = 1436/1610 x 100
= 89%

21. Creatinine Height Index
CHI = (24 hr urine creatinine x 100) / (expected 24 hr urine creatinine for height)
CHI = 1436/1596 x 100 = 90%
expected values in table 9-1 (p306)
CHI > 80% = normal
CHI = 60-80% = mild protein depletion
CHI = 40-60% = moderate depletion
CHI < 40% = severe depletion