Nutrition Assessment: Biochemical Assessment

Question 1

What are features of the biochemical analysis

Answer 1

• Can detect sub-clinical deficiences before signs/ symptoms appear
• usually measured by blood and urine samples as they are easily affected by acute changes
• Pt results compared to reference values which may differ with with different labs

Question 2

How does biochemical analysis differ from dietary assessment?

Answer 2

• biochemical or lab values tell you if a individual has a deficiency
• dietary assessment tells you about risk for deficiency

Question 3

What are some common labs done in biochemical analysis?

Answer 3

• CBC (complete blood cell count) - most common standard blood work (can tell if you have infection)
• Hgb
• serum iron
• TIBC
• Albumin
• prealbumin
• blood clotting (INR → international normalized ratio of prothrombin time)
• liver function (AST aspartate aminotransferase, ALT Alanine transaminase)
• Kidney function (BUN or blood urea nitrogen, creatinine)
• Ca2+, PO4-, Mg2+
• Lytes (Na+, K+, Cl-, CO2)
• Serum lipids
• Glucose
• Hb A1C (glycolated hemoglobin)
• CRP (C-reactive protein)

Normal ranges are provided on the test and assignments, but you will need to interpret abnormal/normal values

Question 4

What lab tests are used for protein status?

Answer 4

• blood analysis through serum proteins which is not ideal but still best option → serum albumin & thyroxin binding protein (prealbumin)
• Nitrogen balance
• creatinine excretion

Question 5

Why are serum proteins not ideal for protein status?

Answer 5

• not always representative of protein status
• low sensitivity, low specificity
• affected by many factors

Best option though so still used

Question 6

What factors affect serum proteins?

Answer 6

• protein intake
• protein metabolism/synthesis
• hydration
• medications
• medical condition
• activity level
• pregnancy

Question 7

Features of serum albumin

Answer 7

Half-life of 20 days so it is a better marker of chronic malnutrition, (long-term protein status) and is insensitive to acute nutritional change
* ↓ significantly with overhydration (more fluid on board)
* ↓ significantly with acute illness; influenced by presence of renal or liver disease

Question 8

When is serum albumin measures most useful?

Answer 8

• Pts being followed long term
• Pts with NO acute illness

Question 9

Serum albumin ranges to detect protein status

Answer 9

detects level of visceral protein depletion without confounding variables

Question 10

Features of prealbumin

Answer 10

Gold standard for short term changes in protein status with half-life of 2 days
* sensitive to acute nutritional changes
* ↓ significantly (severe deficit <0.5 g/L) with acute illness

Question 11

When is prealbumin measures most useful?

Answer 11

• Pts being followed in hospital
• Once Pt is recovering

Question 12

Features of nitrogen balance

Answer 12

A measurement that reflects total protein mass by comparing nitrogen losses to nitrogen intake
* requires a 24 hr urine collection
* urea excreted = measure of protein breakdown (nitrogen intake - nitrogen losses)

Question 13

Where is nitrogen balance used?

Answer 13

Some specific clinical populations such as ICUs but not very accurate
* Can result in overestimate of nitrogen losses because doesn’t consider miscellaneous nitrogenous losses in skins and hair (up to 8 mg/kg/d).

Question 14

Features of creatinine excretion

Answer 14

Reflects muscle mass and increases with muscle wasting

Question 15

Where is creatinine excretion measured?

Answer 15

used in some specific clinical populations such as ICUs with bedridden patients

Question 16

What nutrients should be checked if pt is anemic?

Answer 16

B12, folate and iron as they are all needed for RBC synthesis and may account for different types of anemic condition.

Question 17

What are the types of anemia?

Answer 17

• anemia of chronic disease (which is not iron deficiency anemia)
• anemia due to dietary deficits (eg iron, B12, folate etc)
• anemia due to iron losses/malabsorption of iron (Celiac Disease, excessive menstrual losses, GI bleeds, infection like Giardia etc)

Question 18

Purpose of CBC with anemic patient

Answer 18

differentiate between anemia of chronic diseases vs dietary intake or both

Question 19

B12 and folate deficiency anemia

Answer 19

megaloblastic anemia → lack of vitamin B12 or folate causes the body to produce abnormally large red blood cells (but not as red) that can’t function properly

Question 20

What conditions may lead to B12 and folate deficiency anemia

Answer 20

• chronic disorders (liver disease, kidney disease, alcoholism)
• malabsorption diseases (celiac)
• pts with short gut and missing duodenum where B12 is absorbed
• dietary → seniors, vegans

Question 21

What are the stages of iron deficiency?

Answer 21

• stage 1 depleted stores: Storage (ferritin) = liver, bone marrow, spleen
• stage 2 early functional iron deficiency: Transport (transferrin)
• stage 3 iron deficiency anemia : Essential (Hgb) = RBC, myoglobin, enzymes

Question 22

What is iron deficiency anemia considered a clinical deficiency?

Answer 22

Once all storage and transport iron is used up

Question 23

What does low ferritin mean?

Answer 23

Risk goes up to develop IDA

Question 24

What elements are considered when diagnosing IDA?

Answer 24

• RBCs (Hgb)
• ferritin
• transferrin
• saturation (Fe/TIBC)

Latter 3 are typically in renal services vs. CBC

Question 25

RBCs in diagnosing IDA

Answer 25

* typically ↓ Hgb (gives diagnosis of anemia) * Hematocrit (HCT); gives information about iron content in RBC; typically, but not always ↓; A low HCT: hypochromic → lighter brown, not as red * Mean cell volume (MCV): gives information of size/volume; typically ↓. A low MCV would be a microcytic anemia → looks more shrivelled * May have increased # of reticuloycytes (immature RBC); compensatory mechanism * May have modestly elevated platlet counts (mild thrombocytopenia) due to high erythopoietin levels; all compensatory ## Footnote Combo of HCT and MCV is common

Question 26

ferritin in diagnosis of IDA

Answer 26

Typically low and is very sensitive of iron depletion in body; but may be difficult to assess if patient has chronic inflammation where values may be elevated (even in presence of iron deficiency anemia). * Ferritin may be elevated in patients with Inflammatory Bowel Disease, Rheumatoid Arthritis, during acute and chronic infections even when patient is iron deficient!

Question 27

transferrin in diagnosis of IDA

Answer 27

(typically high which signifies less iron in the body) is main iron transport protein. Typically levels increase in iron deficiency anemia so as to maximize the amount of iron sent to the bone marrow

Question 28

serum iron/TIBC saturation

Answer 28

transferrin saturation is a reflection of reflection of how well free iron binds to the transferrin molecule and how sufficient/deficient iron (free) is present. Usually ↓ * Serum iron (free) not part of the HgB in RBC which may or may not be low in iron deficiency anemia but often ↓ * TIBC: surrogate marker of transferrin levels; blood test that measures the ability of iron(free) to bind to the transferrin protein; typically ↑ in iron deficiency anemia.

Question 29

Ranges for transferrin saturation

Answer 29

Typically females are between 15-50% and males 20-50%; may vary in pediatric populations. * <5% is indicative of iron deficiency anemia

Question 30

Top reasons for IDA

Answer 30

* menses * poor intake

Question 31

Common screening tool for IDA

Answer 31

Ferritin is often used as the screening tool to screen for IDA, particularly in young females but consider other clinical info * asking about menstrual losses in females, dietary intake, reason for other sources of blood losses (e.g presence of chronic disease). * Consider the sources of heme and non-heme iron.

Question 32

Describe CRP

Answer 32

C-reactive protein → A marker of acute inflammation and infection that is highly sensitive, individual and nonspecific * cancer, CVD, TB, pneumonia, Inflammatory Bowel Disease, undiagnosed Celiac * ICU patients: recent surgery, trauma, respiratory, renal, and coagulation failures

Question 33

Where is CRP tests useful?

Answer 33

More useful for determining disease progress and effectiveness of treatments * positively associated with mortality rates * if high in the presence of no disease it is very important to look at

Question 34

CRP ranges

Answer 34

* normal is about 1-2 mg/L * cut-off is 7 mg/L with illness around 8-10 mg/L

Question 35

What is BUN

Answer 35

Blood urea nitrogen → The concentration of nitrogen (as urea) in the serum and not in RBCs (blood)

Question 36

What might high BUN be related to?

Answer 36

* Acute or chronic kidney disease with high creatinine and urea * Dehydration * Excessive protein intake (diet or amino acid infusions via parenteral nutrition) * Meds such as corticosteroids, tetracycline (antibiotics) * Obstruction of ureter, bladder or urethra * After intense cardio such as ultra marathon with skeletal muscle breakdown

Question 37

# What What might low BUN be related to?

Answer 37

* Malnutrition * Profound liver disease (↓synthesis)

Question 38

Describe creatinine

Answer 38

Produced in the muscle, creatinine is a spontaneous decomposition product of creatine and creatine phosphate (for ATP generation)

Question 39

High creatinine may be related to...

Answer 39

* Impaired renal function * Rhabdomyolysis (the destruction or degenerative of skeletal muscle tissue) * Meds such as NSAIDs, cyclosporine (immunosuppressant)

Question 40

Low creatinine may be related to...

Answer 40

* Decreased hepatic synthesis of creatine (precursor) * Decreased muscle mass (e.g. elderly, amputation, malnutrition, muscle wasting)

Question 41

When might a healthy person have low creatinine?

Answer 41

hard training such as ultra running

Question 42

How many times should lab tests be done?

Answer 42

always need blood tests or other tests done about 2-3 times before making diagnosis * need to look at bloodwork, nutrition, disease and put pieces together