Biochemical Analysis

whole blood

collected with an anti-coagulant in the tube, contains RBCs, WBCs, and platelets

serum

fluid obtained after blood is clotted and clot is removed, does not contain RBCs and WBCs

Plasma

transparent liquid component of blood

type of specimens beyond blood

urine, stool, breath, saliva, sweat, etc

static assay

measures actual level of a nutrient in a specimen, ex: serum iron

functional assay

measure of a biochemical or physiological activity that depends on the nutrient of interest; ex: serum ferritin

somatic protein

protein found in skeletal muscle

visceral protein

protein made from organs, mostly the liver (non-skeletal protein)

Creatine Height Index (CHI)

CHI=24hr urine creatinine/ expected 24 hr urine creatinine

Limitations of CHI

requires 24hr urine collection for accuracy

standards don’t account for age, disease, physical training, frame size, or weight

interpret CHI result

60-80%=mild skeletal muscle depletion

40-59%=moderate skeletal muscle depletion

<40%=severe skeletal muscle depletion

Equation for N2 balance

(dietary protein intake x 0.16) -(UUN+4)

positive acute phase proteins

proteins increase with inflammation (CRP, ESR, hsCRP)

negative acute phase proteins

proteins decrease with inflammation (albumin, pre-albumin, transferrin)

albumin

most abundant serum protein; not a great marker for nutrition status because acute stress and inflammation decrease synthesis rate

pre-albumin

shorter half life than albumin, so it responds quickly to nutrition intake

associated with retinol binding protein

retinol binding protein (RBP)

transports vitamin A, short half life (12hrs)→better indicator of recent dietary intake than nutrition status

C reactive Protein

released during periods of inflammation

if high, do not use negative acute phase proteins to assess nutrition status

high sensitivity CRP

predictor of coronary heart disease independent of lipid status, monitors chronic subclinical inflammation of atherosclerosis and rheumatoid arthritis

hematological assessment

evaluation of size, shape, and color of RBCs; key to diagnosing anemias of dietary deficiencies and chronic disease

hemoglobin

delivers O2 and picks up CO2

indirect indicator of iron deficiency→ iron status may be depleted before HgB is affected

hematocrit (Hct)

% of blood volume made up of RBCs; decreased in iron deficiency but not a great marker for anemia since it can also be altered due to hydration status

mean corpuscular volume (MCV)

measure of size of RBCs

microcytic: RBCs too small

macrocytic: RBCs too big

mean corpuscular hemoglobin (MCH)

estimates the amount of hemoglobin in each RBC

abnormal levels seen in Fe deficiencies and other anemias

serum iron

measures the amount of iron in the blood

ferritin

storage form of iron, good estimate of iron stores as it is the first to change in iron deficiency

total iron binding capacity (TIBC)

measures how well iron attaches to transferrin and other proteins in the blood

transferrin

transports iron, usually around 30% of iron binding sites are saturated, but % is lower when iron is low

megablastic anemia

abnormally large RBCs with a low O2 carrying capacity; indicates a folate or vitamin B-12 deficiency

pernicious anemia

vitamin B12 deficiency due to absence of intrinsic factors; could be due to stomach lining atrophy and inflammation

microcytic anemia

MCV RBC <80, indicates iron deficiency

sodium

concentrations track poorly with the need for repletion and are typically more reflective of body water than Na balance

potassium

regulates ICF volume, nerve conduction, and contraction of all muscle types ; abnormalities are often life threatening

chloride and acetate

extracellular anions that maintain osmotic pressure and acid/base balance

calcium

around 1% located in body fluids, the rest in bones and teeth

serum levels are not a good indication of dietary intake or bone levels

magnesium

mineral in ICF necessary for energy metabolism and assists in maintaining the Ca and phosphorus homeostasis

phosphorus

intracellular anion essential for metabolism of all substrates

Tests that measure diabetes

fasting plama glucose >126mg/dL

HbA1C > 6.5%

2 hr post post glucose test >200mg/dL

symptoms of diabetes + casual plasma glucose concentration >200mg/dL

serum creatinine

increased in kidney disease, decreased in malnutrition

BUN (blood urea nitrogen)

increased in kidney disease and protein catabolism

bilirubin

waste product primarily produced by normal breakdown of heme; processed in liver to allow for elimination from body

total cholesterol

decreased in malnutrition and increased in genetic disorders and over nutrition; Ideal level: <200mg/dL

triglycerides

increased in glucose intolerance and non-fasting states

ideal level: <100mg/dL

Which labs are often elevated during dehydration?

serum sodium, BUN, serum osmolality, and urine specific gravity (concentration of particles and solutes in urine compared to pure water)

Characteristics of an ideal nutrition biomarker

short circulation half life (<2days)

rapid response to improved nutrient status

quickly reflects decreased intake

indicates current nutrition status

accurately reflects degree of deficiency

not affected by non-nutritional factors