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Issues with Lab Data
- Availability of tests in clinical practice
- Reliability of test in predicting malnutrition
- Range of normal values sometimes varies, depending on laboratory
- Some dependent on age & gender
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Static Assays
- Actual level of nutrient
- Examples: Serum iron or vitamin D
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Functional Assays
- Physiological activity that depends on nutrient status
- Examples: Serum ferritin in blood reflects iron storage
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Net Protein Loss
- Starts off somatic, followed by visceral protein loss
- Loss of >30% body protein
- -Decreased immunity and muscle strength
- -Increased mortality
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Protein-Calorie Malnutrition
- Serum albumin
- Serum transferrin
- Serum prealbumin
- All are:
- -Synthesized in liver
- -Altered by hydration state
- -Negative acute phase respondents
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Albumin, Transferrin, Prealbumin
- Often are maintained at normal levels during protein deprivation
- -But can be used as one indicator of nutrition status when inflammation not present
- Can serve as indicators of patients who are most at risk of developing nutrition deficits and need extensive nutrition monitoring
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Acute Stress
Monitored by c-reactive protein and erythrocyte sedimentation rate
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C-Reactive Protein
- Increases early in acute stress
- Proportional to amount of stress
- A positive acute phase protein
- Occurs within hours
- Hs-CRP: high-sensitivity CRP being used as predictor of coronary and stroke events
- •Not a marker of acute stress
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Erythrocyte Sedimentation Rate
>100 mm/hr has a 90% predictive value for serious underlying disease
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Nitrogen Balance
- Measures balance between nitrogen intake from protein and nitrogen loss
- N intake (g/24h) - (urinary urea N
- [g/24h] + 3-5 g/24h)
- Can see dramatic negative values- nitrogen is being excreted faster than being taken in
- Visceral protein
- Have to get an accurate urine sample
- -0 + or – 2
- The persons renal function must be normal in order to
- work
- -IF it’s diminished there are factors that you can use
- to fix it
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Urinary Creatinine/Height Index
- Rate of creatinine formation is proportional to muscle mass
- 24 hour collection used
- Creatine is found in the muscles as creatine phosphate
- -Continuously degraded to creatinine
- -Only works when renal system is working properly
- Won’t see very often
- Used in large medical centers that are involved in
- research studies
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Urinary 3-Methylhistidine
- A marker of breakdown of myecin and actin
- Also reflects muscle mass
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Immune Function
- Total lymphocyte count
- Delayed cutaneous hypersensitivity
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Total Lymphocyte Count
- <1500/mm3
- If a person has an infection, lymphocyte count goes up
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Delay Cutaneous Hypersensitivity
- A test that looks at the skin reaction to various antigens
- -Like a TB test
- -If a person is malnourished, the immune response won’t occur (red bump)
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Comprehensive Metabolic Panel
- Use to screen for nutrition related health conditions and monitoring MNT
- Look for nutrition-specific laboratory data
- Has the electrolytes, serum glucose, serum creatinine, albumin, BUN & urea, enzymes, bilirubin, calcium, phosphorus and cholesterol & total triglycerides
- Should be done on a fasting patient
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Metabolic Panel: Serum Glucose
- Fasting Normal = 70-99.9 mg/dL
- >100-125 mg/dL = Increased risk for diabetes
- >126 mg/dL = Diabetes mellitus
- Also increases with pancreatitis, trauma, some meds like glucocortocoids
- Use Hemoglobin A1c to reflect glucose control for previous 2-3 months, Normal = < 5.7%; A1c of 6.5% or higher is a criteria for diagnosis of diabetes mellitus
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To Monitor Renal Function
- Blood Urea Nitrogen
- Creatinine
- Both increase with renal disease, and decrease with low protein diets and with negative nitrogen balance
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To Monitor Liver Function
- AST (SGOT):Aspartate aminotransferase
- ALT (SGPT) Alanine aminotransferase
- Alkaline Phosphatase
- GGT:gamma-glutamyl transferase
- All increased in liver disease, but AST reflects damage in many organs and ALKp also reflects bone disease
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Metabolic Panel: Bilirubin
- Byproduct of hemoglobin breakdown in liver
- Increased with gallstones and biliary duct blockage
- •Bile can’t leave liver, so it enters the bloodstream causing jaundice
- Increased with some liver disease
- Jaundice results from increase
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Metabolic Panel: Total Calcium
- Very tightly regulated
- Total Ca = protein-bound and free Ca
- Increase in hyper-parathyroidism, malignancy, excessive Vitamin D
- Decrease in D deficiency, renal disease, Mg deficiency
- Increase in albumin = increase in total Ca
- Some cancers result in increase in calcium
- 50% of calcium is bound to albumin in the bloodstream
- -If protein is low, then you’ll have a lower calcium level
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Metabolic Panel: Total Phosphate
- Increase in renal failure
- Altered by hyper- and hypo-parathyroidism
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Metabolic Panel: Na+
- Reflects total water balance
- Dehydration= decreases
- Overhydrated= increases
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Metabolic Panel: K+
- Must maintain in a normal limit
- Can have serious neurological, muscle problems, and death if high or low
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Metabolic Panel: Cl- & HCO3
Important for acid base balance in the body
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LDL Cholesterol
Normal: <100
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HDL Cholesterol
Normal: <40
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Triglycerides
- Normal: <150
- High risk: >200
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Low Serum Cholesterol
- < 80 mg/dL associated with increased risk of nutritional complications and mortality
- When using as PEM assessment tool, be sure that person is not taking cholesterol-lowering drugs
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Metabolic Syndrome
- Pre-risk for cardiovascular disease
- Increased risk for illness
- Risk factors:
- Abdominal obesity
- -Men: >40
- -Women: >35
- -Triglycerides: >150
- HDL cholesterol
- -Men: <40
- -Women: <50
- Blood pressure: >130/>85
- Fasting glucose: >100
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A1C Test
- Glucose in the serum can enter RBC and bind to hemoglobin (glycosylation)
- –Higher average glucose levels = higher % of hemoglobin that will be glycosylated (or glycated)
- People with diabetes need to keep their level below 7
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Anemia
- Deficiency in size or number of erythrocytes or amount of hemoglobin they contain
- Limits exchange of oxygen and CO2 between blood and tissue cells
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Hemogram
- Complete blood count
- White blood count
- Differential blood count
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Complete Blood Count
- Description of RBC
- •Hemoglobin (Hg)
- •Hematocrit (Hct)
- •RBC count
- •Mean cell volume (MCV)
- •Mean cell hemoglobin (MCH)
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Differential Blood Count
Classes of leukocytes (neutrophils, lymphocytes, monocytes, eosinophils, basophils)
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Microcytic
- <80 fL (MCV)
- Such as iron deficiency
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Normocytic
- 80-99 fL
- If a person is anemic because of blood loss, they have fewer cells, but are normal size
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Macrocytic
- >100 fL (>110 fL)
- Such as folate deficiency
- Such as B12 deficiency
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Classification of Anemia
- Based on:
- -Cell size
- -Hemoglobin content
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Hemoglobin Content
- Hypochromic (pale)
- -Iron deficient
- Normochromic (normal)
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Iron Deficiency Anemia
- Production of microcytic red blood cells and diminished hemoglobin
- –Decreased MCV, MCH
- Last stage of iron deficiency
- –Can result from
- •Low iron intake
- •Increased needs: growth, pregnancy
- •Increased menstrual loss
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Stages of Iron Deficiency
- Stage 1- moderate depletion of iron stores
- Stage 2- severe depletion of iron stores
- Stage 3- start seeing dysfunction of cell, iron depletion
- Stage 4- anemia dysfunction, fatigue, anorexia, increased risk of infection, decreased exercise, abnormal cognitive development
- Physical signs- pale skin, nails
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Tests for Iron Deficiency
- Serum iron
- Total iron-binding capacity
- Transferrin saturation
- Free-erythrocyte protoporphyrin
- Serum ferritin
- Serum transferrin receptor test
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Iron Deficiency: Serum Iron
- A poor indicator of iron status because it does not change until stage 3 of deficiency
- Not sensitive to early iron deficiency
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Iron Deficiency: Total Iron-Binding Capacity
- Indirect measure of transferrin
- Transport protein is synthesized in the liver, transferrin has binding sites for iron
- Total capacity goes up
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Iron Deficiency: Transferrin Saturation
- The measure of the % of the binding sites that have iron bound to them
- Value will drop if you have less iron
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Iron Deficiency: Free-Erythrocyte Protoporphyrin
- Will go up in iron deficiency
- Zinc protoporphyrin will go up
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Iron Deficiency: Serum Ferritin
- Readily available
- Storage protein synthesized in the liver
- If you have less iron, this will go down
- One of the most sensetive indicators
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Iron Deficiency: Serum Transferrin Receptor Test
- Sensitive indicator
- The receptor that transferrin binds on to transfer iron from the serum to the hemoglobin
- Tends to go up when iron is low
- Not readily available in clinical practices
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Iron Deficiency: Stage 4
- Erythrocytes start becoming microcytic and hypochromic
- When someone has iron overload disease
- -Transferrin saturation and serum ferratin go up
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B12 Deficiency Tests
- Serum B12
- Serum homocysteine
- Methylmalonic acid (serum or urine)
- Schilling test
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Serum B12
- Readily available
- Not very sensitive
- Just a marker of B12
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Serum Homocysteine
- Readily available
- More sensitive
- When B12 isn't present, this builds up
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Methymalonic Acid
- Readily available
- More sensitive
- Urine is better than serum
- Conversion of methylmalonyl CoA to Succinyl CoA requires B12
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Schilling Test
- Used to measure B12
- Given a dose of B12 to fill up the spaces
- Not given often, just given to diagnosed pernicious anemia
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Folate Deficiency Tests
- RBC folate
- Serum folate
- Serum homocysteine
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RBC & Serum Folate
Readily available
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Folate Serum Homocysteine
Will go up with deficiency
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Vitamin D
- Serum 25-OH-Vitamin D is commonly used marker for D status
- Deficiency = < 30 nmol/L
- >50 nmol/L generally considered adequate for bone and overall health in healthy individuals
- Optimal may be as high as 80 nmol/
- >125 nmol/L may result in adverse effects
- Divide nmol/L by 2.5 to get ng/mL
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