TABLE 17-1

P roperties o f S eru m /P lasm a B io ch em ica l M arkers U sed in th e A ssessm en t o f P rotein E n ergy M aln u trition

Biochemical Marker

Site of Synthesis

and Molecular

Weight

Half-life

in the

Blood

Serum/Plasma

Concentration during

Normal(N), Mild, Moderate,

and Severely Depleted States

Properties and Clinical Utility

Albumin

Liver

M.W.: 66,000

15-19 days

N: 3.5-5.0 g/dl

Mild: 2.8-3.5 g/dl

Moderate: 2.1-2.7 g/dl

Severe: <2.1 g/dl

Transports many endogenous and

exogenous ligands, major determinant of

plasma oncotic pressure. Large body pool

and long half-life makes it a poor index of

acute malnutrition

Transthyretin (also

known as prealbumin)

Liver

plasma circulating

form is a tetramer

composed of four

identical monomers.

M.W.: 55,000

1-2 days

N: 20-40 mg/dl

Mild: 10-15 mg/dl

Moderate: 5-10 mg/dl

Severe: <5 mg/dl

Circulates in plasma in a 1:1 complex with

retinol-binding protein, transports

thyroxine, has a small body pool, and has a

short half-life. Sensitive indicator of

protein deficiency and in the improvement

with protein refeeding.

Retinol-binding

protein (RBP)

Liver

M.W.: 21,000

10-12 hours

N: 3.5-9.0 mg/dl

Circulates in plasma in 1:1 complex with

transthyretin, transports retinol and

thyroxine, plasma levels influenced by

glomerular filtration rate, retinol and zinc

status, considered to be too sensitive and

therefore has limited value

Transferrin

Liver

M.W.: 77,000

8.8 days

N: 225-400 mg/dl

Mild: 150-200 mg/dl

Moderate: 100-150 mg/dl

Severe: <100 mg/dl

Transports iron in the ferric state; serum

levels rise proportional to iron deficiency,

a better marker than albumin however, not

suitable in the short-term hospital setting.