Podcast
Questions and Answers
What is NOT a purpose for laboratory assays?
What is NOT a purpose for laboratory assays?
Which laboratory test assesses the excretory function of the kidneys?
Which laboratory test assesses the excretory function of the kidneys?
How is BUN interpreted in relation to creatinine?
How is BUN interpreted in relation to creatinine?
Which statement correctly describes hypernatremia?
Which statement correctly describes hypernatremia?
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What does the MCV test measure?
What does the MCV test measure?
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What common condition can lead to hypokalemia?
What common condition can lead to hypokalemia?
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What does the electrolyte panel typically NOT include?
What does the electrolyte panel typically NOT include?
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Which condition might result in elevated levels of serum calcium?
Which condition might result in elevated levels of serum calcium?
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What is the normal range for sodium concentration in the blood?
What is the normal range for sodium concentration in the blood?
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Which of the following could cause a false low sodium level?
Which of the following could cause a false low sodium level?
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What is a key function of potassium in the body?
What is a key function of potassium in the body?
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Which test is primarily used to assess liver function?
Which test is primarily used to assess liver function?
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What is NOT a typical feature of microcytic anemia?
What is NOT a typical feature of microcytic anemia?
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What does an AST:ALT ratio greater than 1.0 indicate?
What does an AST:ALT ratio greater than 1.0 indicate?
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What can cause an increase in Alkaline Phosphatase (ALP) levels?
What can cause an increase in Alkaline Phosphatase (ALP) levels?
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Which of the following enzymes is primarily used to diagnose pancreatic issues?
Which of the following enzymes is primarily used to diagnose pancreatic issues?
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What is indicated by a decrease in serum albumin levels?
What is indicated by a decrease in serum albumin levels?
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Which condition is associated with increased total bilirubin levels?
Which condition is associated with increased total bilirubin levels?
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What reflects a patient’s ability to transport iron in the body?
What reflects a patient’s ability to transport iron in the body?
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What does an increase in C-Reactive Protein (CRP) levels signify?
What does an increase in C-Reactive Protein (CRP) levels signify?
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Which negative acute phase protein reflects a decrease in synthesization during inflammation?
Which negative acute phase protein reflects a decrease in synthesization during inflammation?
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Which laboratory marker is likely to remain normal in starvation-related malnutrition?
Which laboratory marker is likely to remain normal in starvation-related malnutrition?
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What condition typically leads to elevated levels of both ALT and AST?
What condition typically leads to elevated levels of both ALT and AST?
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What are increased levels of alkaline phosphatase generally associated with?
What are increased levels of alkaline phosphatase generally associated with?
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What can elevated lipase levels indicate?
What can elevated lipase levels indicate?
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Which enzyme is primarily elevated in liver disease and is mostly found in the liver?
Which enzyme is primarily elevated in liver disease and is mostly found in the liver?
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What condition is most likely associated with elevated serum levels of transferrin?
What condition is most likely associated with elevated serum levels of transferrin?
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Which enzyme is predominantly associated with liver function and is particularly elevated in cases of acute hepatitis?
Which enzyme is predominantly associated with liver function and is particularly elevated in cases of acute hepatitis?
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What does an AST:ALT ratio greater than 1.0 typically suggest?
What does an AST:ALT ratio greater than 1.0 typically suggest?
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Which of the following conditions is associated with increased levels of Alkaline Phosphatase (ALP)?
Which of the following conditions is associated with increased levels of Alkaline Phosphatase (ALP)?
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Which laboratory test is most useful for evaluating liver disease through the analysis of bilirubin levels?
Which laboratory test is most useful for evaluating liver disease through the analysis of bilirubin levels?
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What is a common consequence of decreased serum albumin levels in the body?
What is a common consequence of decreased serum albumin levels in the body?
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What role does Transferrin play in the body related to iron?
What role does Transferrin play in the body related to iron?
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What is a key characteristic of C-Reactive Protein (CRP) regarding its role in inflammation?
What is a key characteristic of C-Reactive Protein (CRP) regarding its role in inflammation?
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In what scenario would prealbumin levels likely decrease significantly?
In what scenario would prealbumin levels likely decrease significantly?
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What does increased amylase primarily indicate?
What does increased amylase primarily indicate?
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Which protein is specifically a negative acute phase protein that decreases greater than 25% during inflammation?
Which protein is specifically a negative acute phase protein that decreases greater than 25% during inflammation?
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When does the plasma level of albumin typically decrease?
When does the plasma level of albumin typically decrease?
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What does a significantly high level of lipase generally indicate?
What does a significantly high level of lipase generally indicate?
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What factors commonly influence liver enzyme levels such as ALT and AST?
What factors commonly influence liver enzyme levels such as ALT and AST?
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What is the normal range for Total Bilirubin levels in mg/dL?
What is the normal range for Total Bilirubin levels in mg/dL?
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What is the primary purpose of laboratory assays in clinical practice?
What is the primary purpose of laboratory assays in clinical practice?
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Which of the following is a common indicator of dehydration based on laboratory data?
Which of the following is a common indicator of dehydration based on laboratory data?
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What does the BUN:Creatinine ratio help evaluate?
What does the BUN:Creatinine ratio help evaluate?
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In the context of hyperkalemia, which of the following is a likely cause?
In the context of hyperkalemia, which of the following is a likely cause?
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Which laboratory test is used to distinguish macrocytic from microcytic anemia?
Which laboratory test is used to distinguish macrocytic from microcytic anemia?
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What reflects the body's ability to balance sodium levels?
What reflects the body's ability to balance sodium levels?
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What is the primary role of the electrolyte panel in laboratory tests?
What is the primary role of the electrolyte panel in laboratory tests?
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Which statement correctly describes a function of total calcium in the body?
Which statement correctly describes a function of total calcium in the body?
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What does a high BUN level combined with a normal creatinine level typically indicate?
What does a high BUN level combined with a normal creatinine level typically indicate?
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What is the expected normal value range for total calcium in the blood?
What is the expected normal value range for total calcium in the blood?
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Which laboratory test provides information specifically about liver function?
Which laboratory test provides information specifically about liver function?
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How are hypernatremia and hyponatremia differentiated in laboratory results?
How are hypernatremia and hyponatremia differentiated in laboratory results?
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What aspect of potassium levels is critical to maintain bodily functions?
What aspect of potassium levels is critical to maintain bodily functions?
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What common lab value is often evaluated alongside sodium and potassium in assessing acid-base balance?
What common lab value is often evaluated alongside sodium and potassium in assessing acid-base balance?
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Which factor can lead to low MCH levels in a blood test?
Which factor can lead to low MCH levels in a blood test?
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Study Notes
Laboratory Data Interpretation
- Purpose: Assess nutrient availability in biological fluids and tissues, identify nutrient deficiencies, monitor patient response to nutritional interventions, and provide physiological and metabolic information.
Specimen Collection
- Common sample types: whole blood, serum, plasma, blood spots, urine, feces.
- Less common samples: saliva, sweat, hair, nails, tissue scrapings, biopsy samples.
Blood
- Total blood volume: 5-6 liters (8% of body weight).
- Blood pH: 7.36-7.44.
- Plasma: Watery liquid component of blood containing water, proteins, electrolytes, clotting factors.
- Serum: Watery portion remaining after removing cells and clot-forming material.
Chemistry Panels
- Basic Metabolic Panel (BMP): Evaluates blood glucose, electrolyte and fluid balance, and renal function (glucose, calcium, sodium, potassium, chloride, bicarbonate, BUN, creatinine).
- Comprehensive Metabolic Panel (CMP): BMP plus albumin, total protein, ALP, ALT, AST, bilirubin.
- Electrolyte Panel: Detects fluid and electrolyte balance problems (sodium, potassium, chloride, bicarbonate).
- Lipid Profile: Evaluates total cholesterol, HDL, LDL, triglycerides.
- Liver Panel: Assesses liver function (ALT, ALP, AST, bilirubin, albumin, total protein, GGT, lactate dehydrogenase (LD), prothrombin time (PT), alpha-fetoprotein (AFP), autoimmune antibodies).
- Renal Panel: Evaluates renal function (sodium, potassium, chloride, CO2, phosphate, calcium, albumin, BUN, creatinine, BUN/creatinine ratio, eGFR, anion gap).
- Thyroid Function: Assesses thyroid function (TSH, T4, T3).
Complete Blood Count (CBC)
- Red Blood Cell Count (RBC): Measures the number of red blood cells.
- Hemoglobin (Hgb): The oxygen-carrying protein in red blood cells.
- Hematocrit (Hct): The percentage of red blood cells in total blood volume.
- Mean Corpuscular Volume (MCV): Average size of red blood cells.
- Mean Corpuscular Hemoglobin (MCH): Average amount of hemoglobin in each red blood cell.
- Mean Corpuscular Hemoglobin Concentration (MCHC): Concentration of hemoglobin in a given volume of packed red blood cells.
- White Blood Cell Count (WBC) & Differential: Measures total number of white blood cells and their subtypes (neutrophils, lymphocytes, monocytes, eosinophils, basophils).
- Platelet Count: Measures number of platelets involved in blood clotting.
Additional Common Labs
- A1C (Glycated Hemoglobin): Measures average blood glucose levels over the past 2-3 months.
- International Normalized Ratio (INR): Measures clotting time (important for patients on blood thinners).
- Prothrombin Time (PT): Evaluates the extrinsic pathway of blood coagulation.
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Inflammatory Markers:
- Prealbumin: Reflects nutritional status, protein synthesis.
- C-Reactive Protein: Indicative of inflammation.
- Specific Nutrient Levels: vitamin D, vitamin B12, folate.
Urinalysis
- A physical and chemical analysis of urine to detect abnormalities.
- Specific Gravity: Measures urine concentration.
- pH: Measures acidity or alkalinity of urine.
- Protein: Detects presence of protein in the urine, indicating kidney problems.
- Glucose: Detects presence of glucose in the urine, indicating diabetes.
- Ketones: Detects ketone bodies in urine, indicating metabolic imbalances.
- Blood: Detects presence of blood in urine, indicating kidney or urinary tract issues.
- Bilirubin: Detects bilirubin, a byproduct of red blood cell breakdown, indicating liver problems.
- Nitrite: Detects bacteria in urine, indicating a urinary tract infection.
- Leukocyte Esterase: Detects white blood cells in urine, indicating inflammation.
Sodium
- Major extracellular cation: Important for maintaining fluid balance, neuromuscular function, and acid-base balance.
- Normal Range: 135-145 mEq/L.
- Hyponatremia (low sodium): Could be caused by low sodium intake, increased fluid intake, increased sodium losses (diarrhea, vomiting, sweating, diuretics), or water retention.
- Hypernatremia (high sodium): Could be caused by inadequate fluid intake (dehydration), excessive sweating, or water loss exceeding sodium loss.
Fluid Assessment
- Indicators of dehydration: dry lips and mouth, tenting of skin, fatigue, irritability, confusion, low urinary output, low pulse and blood pressure.
- Labs: Na and BUN/creatinine ratio may be elevated.
- Fluid restriction may be necessary for: edema, ascites, CHF, renal failure, liver failure.
- Overhydration signs: low blood levels of Na, K, albumin, BUN, Cr, elevated blood pressure, edema.
Potassium
- Principle intracellular cation: Important for maintaining water balance, osmotic equilibrium, acid-base balance, and neuromuscular activity.
- Normal Range: 3.6-5 mEq/L.
- Hyperkalemia (high potassium): Could be caused by decreased potassium excretion (renal failure, potassium-sparing diuretics), metabolic acidosis, excessive potassium intake, or excessive IV potassium administration.
- Hypokalemia (low potassium): Could be caused by inadequate intake, increased losses (diarrhea, vomiting, nasogastric suction), increased renal excretion, or medications (potassium-wasting diuretics, corticosteroids).
Bicarbonate (Total CO2)
- Usually ordered with electrolytes.
- Used to assess acid-base balance, specifically distinguishing respiratory and metabolic acidosis or alkalosis.
- Biochemical marker for renal function.
- Normal Value: 21-28 mEq/L.
Blood Urea Nitrogen (BUN)
- Measures urea in blood: a byproduct of protein metabolism, produced in the liver, and excreted by the kidneys.
- Used to assess kidney excretory function and liver metabolic function.
- Normal Value: 5-20 mg/dL.
- Increased BUN: impaired renal function, excessive protein catabolism, and dehydration.
- Decreased BUN: liver failure and pregnancy.
Creatinine
- Byproduct of muscle metabolism: Formed during the breakdown of creatine phosphate to generate ATP.
- Primarily reflects muscle mass.
- Used to assess kidney excretory function.
- Normal Values: 0.6-1.2 mg/dL (males), 0.5-1.1 mg/dL (females).
- Increased creatinine: impaired kidney function, surgical procedures, or trauma.
- Normally interpreted with BUN, specifically the BUN/creatinine ratio.
BUN:Creatinine Ratio
- Used to distinguish pre-renal, renal, and post-renal causes of kidney failure.
- Normal Ratio: 10:1 to 20:1
- Elevated Ratio: Can be caused by volume depletion, dehydration, urinary tract obstruction, CHF, gastrointestinal bleeding - indicating pre-renal causes.
- Elevated BUN and Creatinine: Suggests kidney failure.
Calcium
- Regulates: nerve transmission, muscle contraction, bone metabolism, blood pressure, blood clotting.
- Regulated by: parathyroid hormone (PTH), calcitonin, vitamin D, phosphorus.
- Used to evaluate: parathyroid function, renal failure, hyperparathyroidism, certain cancers, and bone metastases.
- Normal Range: 8.6-10 mg/dl.
- Total calcium includes both ionized calcium (50%) and calcium bound to albumin (50%). Ionized calcium is the active form.
- Correction for low albumin: (Corrected Ca = ([4 – serum albumin] x 0.8) + measured calcium).
Glucose and Hemoglobin A1C
- Glucose: Normal Value: 70-99 mg/dL (adults, fasting), slightly increased after age 50.
- Severe stress: can lead to hyperglycemia.
- Used to screen for diabetes: Fasting glucose >125 mg/dL indicates diabetes mellitus.
- Used to monitor diabetic patients: Fasting glucose >100 mg/dL indicates insulin resistance.
- Hemoglobin A1C: Measures average glucose concentrations over the past 2-3 months.
- Normal Value: 4-6% (goal for diabetics 6.5% diagnostic).
MCV (Mean Corpuscular Volume)
- Used to distinguish between microcytic and macrocytic anemia.
- Below normal MCV: Microcytic anemia, often associated with iron deficiency.
- Above normal MCV: Macrocytic anemia, often associated with B12 or folate deficiency.
- Calculated by dividing the total volume of packed red blood cells (hematocrit) by the total number of red blood cells.
MCH (Mean Corpuscular Hemoglobin) and MCHC (Mean Corpuscular Hemoglobin Concentration)
- MCH: Measures the amount of hemoglobin in each red blood cell.
- Low MCH: Low amount of hemoglobin present per cell.
- MCHC: Measures the concentration of hemoglobin in a given volume of packed red blood cells.
- Increased MCHC: Hemolytic anemia, sickle cell anemia.
- Decreased MCHC: Hypochromia (pale color, deficiency of hemoglobin), often associated with iron deficiency.
- Normal MCHC in macrocytic anemia.
Anemia
- Deficiency in the size or number of red blood cells or the amount of hemoglobin they contain.
- Types: blood loss, chronic disease, marrow failure, nutritional, congenital (sickle cell).
- Indices: Hgb/Hct, MCV, MCH, MCHC
Macrocytic Anemia
- Associated with folate and B12 deficiency.
- Increased MCV, MCH.
Microcytic Anemia
- Associated with iron deficiency.
- Decreased MCV, MCH.
Thrombocytes (Platelets)
- Normal Range: 150-350,000/mm3
- Function: Blood coagulation and clotting.
- Low platelet count: Can cause bleeding issues.
- High platelet count: Can cause clotting issues (thrombosis).### Coagulation Pathway
- Thrombin is a key intermediary in the conversion of fibrinogen to cross-linked fibrin.
- PT/PTT and INR (international normalized ratio) are used to assess coagulation and are related to the time it takes for blood to clot.
Alkaline Phosphatase (ALP)
- ALP is an enzyme found in all tissues, particularly high in bone, liver, and bile ducts.
- Normal values are 30-120 units/L.
- Increased ALP levels can indicate liver cancer, cirrhosis, hepatitis, bile duct blockage, bone disorders, and cancer metastasis to bone.
- ALP is normally elevated in the third trimester of pregnancy, adolescents, and children.
- Decreased ALP levels can be caused by zinc deficiency and hypophosphatasia.
Alanine Aminotransferase (ALT) & Aspartate Aminotransferase (AST)
- ALT, formerly known as SGPT, is an enzyme found primarily in the liver, with smaller amounts in the kidneys, heart, and skeletal muscle.
- Normal ALT values are 4-36 units/L.
- AST, formerly known as SGOT, is an enzyme found primarily in the heart, liver, and skeletal muscle, but also in kidneys, brain, pancreas, spleen, and lungs.
- Normal AST values are 0-35 units/L.
- Increased levels of both ALT and AST can indicate liver damage or disease.
- AST/ALT ratio can be used to identify specific liver conditions.
Bilirubin
- Bilirubin is a component of bile and is present in both conjugated (direct) and unconjugated (indirect) forms.
- Total bilirubin represents the sum of both forms.
- Normal total bilirubin levels are 0.3-1.0 mg/dl, indirect bilirubin levels are 0.2-0.8 mg/dl, and direct bilirubin levels are 0.1-0.3 mg/dl.
- Increased bilirubin levels can indicate liver dysfunction, blood disorders, or biliary tract blockage.
Amylase & Lipase
- Amylase is a pancreatic enzyme involved in starch hydrolysis.
- Increased amylase levels are seen in pancreatitis, cholecystitis, and alcohol poisoning.
- Decreased amylase levels can be caused by advanced cystic fibrosis and hepatitis.
- Lipase is a pancreatic enzyme involved in lipid breakdown.
- Elevated lipase levels indicate acute pancreatitis and pancreatic duct obstruction.
- Decreased lipase levels can be caused by cystic fibrosis and permanent pancreatic damage.
Arterial Blood Gases
- Arterial blood gases measure pulmonary function.
Hepatic Proteins
- The acute phase response is a nonspecific reaction to inflammation, leading to changes in plasma protein synthesis.
- Positive acute phase proteins increase in synthesis during the acute phase response, while negative acute phase proteins decrease.
- Changes in these proteins are proportional to the severity of the inflammatory insult.
- These proteins are indicators of inflammation, not nutritional status.
- These proteins do not typically respond to feeding interventions in the context of inflammation.
Inflammatory Markers - Albumin
- Albumin is the most abundant plasma protein, representing 55-60% of total serum protein.
- Albumin synthesis takes place exclusively in the liver.
- It plays a crucial role as a transport protein and helps maintain plasma colloidal osmotic pressure.
- Decreases in albumin levels can be attributed to decreased synthesis, increased degradation, or changes in fluid distribution.
- Albumin levels often decrease in acute inflammation, making interpretation in acute care challenging.
Inflammatory Markers - Transferrin
- Transferrin is a protein that transports iron to the bone marrow for hemoglobin production.
- Transferrin synthesis is regulated by iron storage levels.
- Transferrin levels decrease in acute inflammatory reactions, chronic infection/illness, malignancies, and liver disease.
- Transferrin levels increase during pregnancy.
- Decreased levels reflect inflammation and are not useful as a measure of protein status.
- Transferrin can be measured directly or estimated using the total iron-binding capacity (TIBC).
Inflammatory Markers - Prealbumin (PAB) & Retinol Binding Protein (RBP)
- Prealbumin:
- Transports thyroid hormones (T3 and T4).
- Transports vitamin A in combination with retinol binding protein.
- Decreased levels are seen in inflammation and may not improve with intensive nutrition support.
- Low levels can also be caused by zinc deficiency.
- Retinol binding protein:
- Transports retinol (vitamin A metabolite).
- Circulates in a complex with prealbumin.
- Decreases with starvation-related malnutrition and inflammatory stress.
Inflammatory Markers - C-Reactive Protein (CRP)
- CRP is a positive acute phase reactant and non-specific marker of inflammation.
- Its exact function is unclear, but it increases in the early stages of acute stress.
- CRP can help estimate and monitor the severity of illness and can increase up to 1000-fold depending on the intensity of the stress response.
- A decrease in CRP levels indicates a patient is entering the anabolic phase of the inflammatory response and beginning recovery.
Summary of Inflammatory Markers
- Negative acute phase proteins (synthesis decreases >25%): albumin, transferrin, prealbumin, and retinol binding protein.
- Positive acute phase proteins (synthesis increases >25%): CRP, fibrinogen, prothrombin, and others.
Laboratory Data
- Purpose of lab assays:
- Estimate nutrient availability in biological fluids and tissues
- Identify clinical and subclinical nutrient deficiencies
- Monitor patient's response to nutritional intervention
- Support subjective judgment and clinical assessment findings
- Laboratory data ≠ assessment of nutritional status, it provides physiologic and metabolic information
- Example: Serum Calcium
- Considerations for interpreting lab data:
- No single lab test can diagnose; need to use supporting data (physical findings, anthropometrics, reported symptoms, diet analysis)
- Look for directions and trends in data
- Improvement in lab data may not confer clinical benefit
- Results not consistent with the clinical picture should be repeated
Specimen Types
- Blood
- Serum
- Plasma
- Blood spots
- Urine
- Feces
- Less common: saliva, sweat, hair, nails
- Other tissues: scraping, biopsy samples
Blood
- Total volume of blood: 5-6 liters (8% body weight)
- pH of blood: 7.36-7.44
- Plasma: The liquid component of blood containing water, blood proteins, inorganic electrolytes, clotting factors
- Serum: The watery portion of blood remaining after removal of cells and clot-forming material
Chemistry Panels
- Basic Metabolic Panel (BMP):
- Blood glucose, electrolyte and fluid balance, renal function
- Glucose, Ca, Na, K, Cl, HCO3, BUN, Cr
- Comprehensive Metabolic Panel (CMP):
- BMP + 6 additional tests: albumin, total protein, ALP, ALT, AST, bilirubin
- Electrolyte Panel:
- Helps detect problems in fluid and electrolyte balance
- Na, K, Cl, Bicarbonate
- Lipid Profile:
- Total cholesterol, HDL, LDL, Triglycerides
- Liver Panel (Hepatic Function Panel, Liver Function Tests, LFTs):
- ALT, ALP, AST, Bilirubin, Albumin, Total Protein
- May also include GGT, LD, PT, AFP, autoimmune antibodies (ie ANA, SMA)
- Renal Panel (Kidney Function Panel):
- Na, K, Cl, CO2, Phosphorus, Ca, Albumin, BUN, Cr
- May also include BUN/Cr ratio, eGFR, anion gap
- Thyroid Function:
- TSH (thyroid-stimulating hormone), T4, T3
Complete Blood Count (CBC)
- Red blood cell count (erythrocytes, RBC)
- Hemoglobin
- Hematocrit
- MCV, MCH, MCHC
- White blood cell count (leukocytes, WBC)
- Differential:
- Neutrophils
- Lymphocytes
- Monocytes
- Eosinophils
- Basophils
- Platelets (thrombocytes)
Additional Common Lab Tests
- A1C
- INR
- PT
- Inflammatory Markers
- Pre-albumin
- C-Reactive Protein
- Specific Nutrients
- Vitamin D
- Vitamin B12
- Folate
- Many others
Urinalysis
- Specific gravity
- pH
- Protein
- Glucose
- Ketones
- Blood
- Bilirubin
- Nitrite
- Leukocyte esterase
- Urine: mixture of water, inorganic salts and organic compounds
- Water-soluble vitamins/metabolites may be present
- Normal excretion - 600-2500 ml/day
- Normal pH - 4.6-8; Protein: 2-8mg/dL
- Specific gravity (density) - 1.005-1.025
Sodium
- Major cation of extracellular fluid; extracellular sodium concentrations (135mEq/L) much higher than intracellular levels (10mEq/L)
- Regulates extracellular and plasma volume, important in neuromuscular function, maintenance of acid-base balance
- Reflects relationship between total body sodium and extracellular fluid volume, and balance between dietary intake of sodium and renal excretory function
- 90-95% normal body sodium loss is through urine (rest in feces, sweat)
- Indirectly measures hydration status: ↑ dehydration, ↓ overhydration
- Normal Range: 135-145 mEq/L
Hyponatremia
- ↓ sodium intake (Na restricted diet)
- In most cases: reflects ratio of water to sodium
- ↑ fluid intake (excessive water orally, IV without electrolytes)
- ↑ losses: diarrhea, vomiting, fistulas, excessive sweating, diuretic administration, Addison’s disease (decreased aldosterone)
- ↑ water retention: SIADH (increased anti-diuretic hormone)
- ↑ fluid accumulation in the body (edema)
- Disease states: CHF, liver failure, renal failure
- False ↓: Na stores intact but water intake is excessive, dilution
Hypernatremia
- ↑ oral sodium intake –rarely (typically renal excretion compensates)
- Reflects change in water status
- ↓ inadequate fluid intake (dehydration)
- ↑ extra-renal water loss (excessive sweating, open wounds, hyperventilation)
- Water loss exceeds sodium loss
- Cushing’s syndrome, diabetes insipidus (diluted urine)
Fluid Assessment
- Indicators of dehydration:
- Dry lips and mouth
- Tenting of skin
- Fatigue
- Irritability
- Confusion
- Low urinary output
- ↓ pulse and blood pressure
- Labs: ↑ in sodium, ↑ BUN/Creatinine Ratio
Fluid Restriction
- May need fluid restriction with
- Edema or ascites
- CHF, Renal Failure, Liver Failure
- Signs of overhydration:
- ↓ blood levels of Na, K, albumin, BUN, Cr
- ↑ blood pressure
- Presence of edema
Potassium
- Principle intracellular cation
- Involved in maintaining normal water balance, osmotic equilibrium, acid-base balance; regulation of neuromuscular activity (concentrations of K & Na determine membrane potentials in nerves, muscles)
- Regulates osmolarity of ECF by exchanging with sodium
- Used in the evaluation of acid-base balance and kidney function
- Normal Range: 3.6-5 mEq/L
Hyperkalemia
- Inadequate excretion of potassium (common in renal failure)
- Excessive use of potassium-sparing diuretics (inadequate excretion)
- Metabolic acidosis; H+ ions excreted to correct acidosis, K ions retained
- Excessive intake: potassium-containing salt substitutes (KCl instead of NaCl)
- Excessive IV potassium (IV fluids)
Hypokalemia
- Inadequate dietary intake
- Increased losses: diarrhea, vomiting, nasogastric suction
- Increased renal excretion
- Medications: ie potassium-wasting diuretics, corticosteroids
Bicarbonate, Total CO2
- Usually ordered along with Na, K, Cl as part of electrolyte panel; or as part of routine CMP (common metabolic panel)
- Used to assess acid-base balance; helpful in distinguishing between respiratory vs metabolic acidosis or alkalosis
- Biochemical marker for the renal system
- Normal Value: 21-28 mEq/l
Blood Urea Nitrogen (BUN)
- Measures the amount of urea in the blood
- Urea is a byproduct of protein metabolism
- Formed in the liver, excreted by the kidneys
- Used to assess excretory function of kidneys, metabolic function of liver
- Primarily evaluated along with creatinine (Cr)
- Normal Value: 5-20 mg/dL
- Increased in those with impaired renal function, excessive protein catabolism
- Decreased in those with liver failure, also with pregnancy
Creatinine
- Byproduct of metabolism of muscle creatine phosphate to form ATP
- Determined by muscle mass
- Used to assess excretory kidney function
- Normal Values:
- 0.6-1.2 mg/dL (males)
- 0.5-1.1 mg/dL (females)
- Elderly have less muscle mass and lower values
- Levels are interpreted in conjunction with BUN (ratio)
- Increased with impaired kidney function, and after surgery or trauma
- Main lab value used to assess kidney functions
- If BUN values are high but not creatinine values, that usually indicates dehydration
BUN:Creatinine
- Laboratory evaluation of kidney failure
- Ratio of BUN:Creatinine is usually between 10:1 to 20:1
- When BUN rises but creatinine does not (increased ratio)
- Reduced blood flow to kidneys, volume depletion, dehydration, urinary tract obstruction, CHF, gastrointestinal bleeding
- When both BUN and creatinine rise
- Kidney failure
Calcium
- Regulates nerve transmission, muscle contraction, bone metabolism, and blood pressure; necessary for blood clotting
- Regulated by the parathyroid hormone (PTH), calcitonin, vitamin D, and phosphorus; complex regulation system: kidney, gastrointestinal tract, bone
- Used to evaluate parathyroid function; used to monitor renal failure, hyperparathyroidism, certain cancers, bone metastases
- Normal: 8.6-10 mg/dl
- Total calcium includes both ionized calcium (50%) and calcium bound to albumin (50%), ionized calcium active form, not affected by protein levels
- Correction for low albumin: Corrected Ca = ([4 – serum albumin] x 0.8) + measured calcium
Glucose and Hemoglobin A1C
- Glucose
- Normal Value: 70-99 mg/dL (adults, fasting)
- Increased slightly after age 50
- Severe stress from injury or surgery → hyperglycemia
- Normal Value: 70-99 mg/dL (adults, fasting)
- Used to screen for diabetes and monitor diabetic patients
- Fasting glucose >125 mg/dL indicates diabetes mellitus
- Fasting glucose >100 mg/dL indicator of insulin resistance
- Hemoglobin A1C
- Normal Value: 4-6% (goal for diabetics 6.5% diagnostic
- Measures average glucose concentrations x past 2-3 months
Mean Corpuscular Volume (MCV)
- Measures the average size of red blood cells
- Helps distinguish between microcytic and macrocytic anemia:
- Below normal: microcytic, in presence of iron deficiency
- Above normal: macrocytic, in presence of B12 or folate deficiency
- Total volume of packed red blood cells (hematocrit) / total # RBC
- Hematocrit (Hct) = % of RBCs in total blood volume
MCH & MCHC
- MCH: mean corpuscular hemoglobin (27-31 pg/cell)
- Hgb / # of RBC
- Amount of Hgb in each RBC
- Low MCH means low amount of Hgb present per red blood cell
- Influenced by size of the RBC, and amount of Hgb in relation to size of RBC
- Mirrors MCV (bigger RBC tend of contain more Hgb)
- MCHC: mean corpuscular hemoglobin concentration (32-36g/dL, 32-36%)
- Measure of Hgb concentration in a given volume of packed RBCs
- Helps to distinguish iron-deficiency anemia
- Increased: hyperchromia
- Hemolytic anemia, sickle cell anemia
- Decreased: hypochromia (pale color, deficiency of hemoglobin)
- Iron deficiency
- Normal in macrocytic anemia
- Increased: hyperchromia
Anemia
- Deficiency in size or number of RBCs or amount of hemoglobin they contain (could be blood loss, chronic disease, marrow failure, nutritional, congenital such as sickle cell)
- Indices:
- Hgb/Hct, MCV, MCH, MCHC
- Macrocytic Anemia:
- Folate
- B12 - Increased MCV, MCH
- Microcytic Anemia:
- Fe - Decreased MCV, MCH
Thrombocytes
- Platelets (150-350,000/mm3)
- Function in the coagulation/clotting of blood
Fibrinogen to Fibrin Pathway
- Thrombin, along with complement proteins, plays a crucial role in converting fibrinogen to fibrin.
- PT/PTT (Prothrombin Time/Partial Thromboplastin Time) and INR (International Normalized Ratio) are used to assess this pathway.
- INR reflects the ratio of a patient's PT to a laboratory's control value.
Alkaline Phosphatase (ALP)
- ALP is an enzyme found in various tissues, with high concentrations in bone, liver, and bile ducts.
- It reflects liver function and can help screen for bone abnormalities.
- Normal values range from 30-120 units/L.
- Elevated ALP levels indicate liver cancer, cirrhosis, hepatitis, bile duct blockage, Paget's disease, and bone metastasis.
- ALP levels are normally elevated during the third trimester of pregnancy and in adolescents and children.
- Low levels can be caused by zinc deficiency and hypophosphatasia (a rare genetic disorder).
Alanine Aminotransferase (ALT) & Aspartate Aminotransferase (AST)
- ALT, formerly known as SGPT (serum glutamic pyruvic transaminase), is mainly found in the liver, kidneys, heart, and skeletal muscle.
- Normal ALT values are between 4-36 units/L.
- Elevated ALT levels indicate acute or chronic hepatitis, cirrhosis, and liver cancer.
- AST, previously known as SGOT (serum glutamic oxaloacetic transaminase), is primarily found in the heart, liver, and skeletal muscle; also present in kidneys, brain, pancreas, spleen, and lungs.
- Normal AST values range from 0-35 IU/L.
- Increased AST levels are associated with liver damage, myocardial infarction, acute pancreatitis, and severe muscle injury.
- Both ALT and AST reflect liver function and are used to assess liver damage.
- They are also monitored in patients receiving parenteral nutrition.
AST:ALT Ratio
- AST:ALT ratio helps differentiate various liver conditions.
- AST:ALT > 1.0 suggests alcoholic cirrhosis, liver congestion, or metastatic liver tumor.
- AST:ALT < 1.0 indicates acute hepatitis, viral hepatitis, or infectious mononucleosis.
Bilirubin
- A major constituent of bile.
- Total bilirubin consists of conjugated (direct) and unconjugated (indirect) bilirubin, with unconjugated accounting for 70-85%.
- Normal values:
- Total: 0.3-1.0 mg/dl
- Indirect: 0.2-0.8 mg/dl
- Direct: 0.1-0.3 mg/dl
- Reflects liver function and is helpful in evaluating blood disorders and biliary tract blockage.
- Elevated bilirubin levels are linked to pancreatic cancer, liver metastasis, gallstones, and biliary duct diseases.
Amylase & Lipase
- Amylase:
- Pancreatic enzyme responsible for starch hydrolysis.
- Elevated levels indicate pancreatitis (primary), cholecystitis, and alcohol poisoning.
- Low levels are seen in advanced cystic fibrosis and hepatitis.
- Lipase:
- Pancreatic enzyme involved in lipid breakdown.
- Increased levels are associated with acute pancreatitis and pancreatic duct obstruction.
- Decreased levels are found in cystic fibrosis and permanent pancreatic damage.
Arterial Blood Gases
- Measure pulmonary function.
- Will be covered in detail during a pulmonary lecture.
Hepatic Proteins
- The acute phase response is a nonspecific reaction to inflammation, causing significant metabolic changes.
- During this response, certain plasma protein synthesis increases (positive acute phase proteins) or decreases (negative acute phase proteins) by at least 25%.
- These protein changes are proportional to the severity of the physiological insult.
- They are indicators of inflammation, not nutritional status.
- Lab values should be interpreted cautiously, as they reflect the magnitude of the inflammatory response rather than oral protein intake.
- These indicators do not generally respond to feeding interventions during inflammation.
Albumin
- The most abundant plasma protein, comprising 55-60% of total serum protein.
- Albumin is solely synthesized in the liver.
- It serves as a major transport protein for hormones, enzymes, medications, minerals, ions, fatty acids, amino acids, and metabolites.
- Contributes to plasma colloidal osmotic pressure. Reduced serum albumin levels lead to fluid movement from plasma to the interstitial compartment, causing edema.
- Decreased serum albumin levels can occur due to decreased synthesis (to spare amino acids for positive acute phase protein production), increased degradation rate, or fluid distribution changes. Most patients experience at least one of these factors.
- Interpretation in acute care is complex, as changes reflect illness, not nutritional status.
- Plasma albumin levels decline with acute inflammation.
Transferrin
- Transports iron to the bone marrow for hemoglobin production.
- Plasma transferrin levels are controlled by iron storage pool size. When iron stores are depleted, transferrin synthesis increases.
- Levels decrease with acute inflammatory reactions, chronic infection/illness, malignancies, and liver disease but increase during pregnancy.
- Decreased levels reflect inflammation and are not a reliable measure of protein status.
- Can be measured directly or estimated with total iron-binding capacity (TIBC).
- TIBC directly quantifies all proteins available to bind mobile iron.
- % Transferrin saturation = (Serum Fe/TIBC) x 100
Prealbumin (PAB) & Retinol Binding Protein (RBP)
- Prealbumin:
- Transports thyroid hormones (triiodothyronine and thyroxine (T4)).
- Combined with RBP, it transports vitamin A.
- Levels decrease with inflammation and do not improve with aggressive nutrition support.
- Levels are often normal in starvation-related malnutrition but are reduced in well-nourished individuals with recent stress or trauma.
- Serum levels also decrease with zinc deficiency, as zinc is needed for hepatic synthesis and secretion of prealbumin.
- Consider zinc status when interpreting low plasma PAB levels.
- Retinol Binding Protein (RBP):
- Transports retinol (vitamin A metabolite).
- Circulates in a complex with prealbumin (PAB).
- Can decrease with starvation-related malnutrition but also drops with inflammatory stress, and may not improve with re-feeding.
C-Reactive Protein (CRP)
- Positive acute phase reactant.
- Non-specific marker of inflammation.
- Exact function is unclear, but levels increase in the initial stages of acute stress (usually within 4-6 hours of surgery or trauma).
- Helps estimate and monitor illness severity.
- Levels can increase up to 1000-fold depending on the intensity of the stress response.
- When CRP starts to decrease, the patient has entered the anabolic phase of the inflammatory response and recovery begins.
- Once CRP starts to decrease, intensive nutrition therapy may be beneficial.
Inflammatory Markers
- Negative acute phase proteins: synthesis decreases by more than 25%
- Albumin
- Transferrin
- Prealbumin
- RBP
- Positive acute phase proteins: synthesis increases by more than 25%
- CRP
- Fibrinogen
- Prothrombin
- Other proteins
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Description
Test your knowledge on laboratory data interpretation, focusing on nutrient availability and deficiency identification in biological fluids. This quiz covers specimen collection methods, blood composition, and key chemistry panels like BMP and CMP.
