Clinical Chem Exam 1

Metalloproteins

proteins that contain a metal ion

Lipoproteins

contain lipids

Nucleoproteins

proteins with DNA/other nucleic acids

Glycoproteins

<4% of total weight is carbohydrates

Mucoproteins

Carbohydrates make up >4% of total weight

Metabolism of Amino Acids

starts in the gut, absorbed in the jejunum until they reach the AA pools in the liver and other organs that make proteins

Purpose of AA pools

Create reservoir of essential amino acids

Where are most plasma proteins produced?

Liver

Where are immunoglobulins produced?

B cells

Where is hemoglobin produced?

kidneys

Hyperproteinemia/positive nitrogen balance

Intake of N is greater than excretion of urine, can be due to dehydration, diarrhea, DKA, multiple myeloma, HIV/AIDS

Hypoproteinemia/negative nitrogen balance

Less secretion of N than intake or synthesis of protein, can be due to an increase in plasma water, protein loss, decreased intake

Biuret method

based on presence of total peptide bonds

copper sulfate in reagent will interact with peptide bonds to cause a color change to purple

Hemolysis

Occurs before blood sample enters a lab-lysing of red blood cells due to improper blood collection technique

causes interferences in testing and can skew results, especially for potassium levels

Icteremia

High amounts of bilirubin in serum/plasma causing interferences with albumin and electrolyte levels

Seen in liver disease and newborns not A/B/O compatible with mother

Refractometry

A backup method to measuring total protein by measuring the ratio of plasma to serum protein solute in water based on refraction of light by the protein

Turbidimetric assays

Used for fluids that have low protein content

Based on the decrease in light transmission measured due to particles in the sample

Performed by spectrophotometers

Dye used for albumin analysis-most likely

Bromcresol green

Urinary protein analysis

Color change indicator for urine protein concentration

More sensitive to albumin than globulins-will cause a false negative if low albumin but high globulins (multiple myeloma)

Protein electrophoresis

Migration of proteins from cathode to anode on an agarose gel in alkaline buffer (8.6), separation by size and charge

Uses serum protein instead of plasma because serum won’t have a fibrinogen band

How do the normal PE fractions change with active cirrhosis?

Beta gamma bridging

How do the normal PE fractions change with nephrotic syndrome?

Higher than normal albumin and a2 content

How does monoclonal gamopathy change the normal PE fractions?

Lower than normal a-1, a-2, b-1, b-2 fractions, abnormally high gamma fractions

Multiple myeloma and Waldenstrom’s macroglobulenemia

Acute phase reactions are seen on an electrophoresis graph by an:

Increase a1 and a2 PE fractions

Potentiometry

Measure of an electrical potential difference between two electrodes in an electrochemical cells when the cell current is zero

Uses the Nernst equation to detect the electrode’s electrical potential changes with the activity of an ion

Purpose of the reference and indicator electrodes

reference-provides stable, known electric potential

indicator-electrical potential changes based on measured ion

Main potentiometer used in the lab

Ion selective membrane electrodes

Types of ISE electrodes and what they measure

Glass-pH and Na+

Polymer membrane electrodes-pH and electrolytes-main one used

Types of polymer membrane electrodes

Charged, dissociated- Cl- measurement-uses membrane to extract all ions that are positively charged

Charged, associated carriers-not as common, interact specifically with the target ion via ion exchange/complex formation

Neutral ion carriers-most common in labs-ionophore that binds with ion of interest and has selectivity for ion’s size and shape, will carry ion of interest into the membrane to create a potential

Sodium

Major extracellular cation

Controls water distribution and osmotic pressure

Measured with ISE

Is potassium or sodium more affected by hemolysis?

Potassium because it is an intracellular ion-lysis of RBCs leads to falsely elevated levels

Sodium reference range

135-145 mmol/L

128-140 mmol/L (newborns)

Hypoosmotic hyponatremia

Decreased solute and sodium in plasma

Vomiting, diarrhea, diuretics (depletional), SIADH, Cirrhosis, nephrotic syndrome (dilutional)

Can be depletional (more ECF Na+ lost than ECF water loss) or Dilutional hyponatremia (Excess H2O retention)

Hyperosmotic hyponatremia

Increase of solute in plasma causing sodium to shift into cells

Most common in diabetes with increased blood sugar (hyperglycemia)

Isoosmotic hyponatremia

Pseudo due to electrolyte exclusion effect

Electrolyte exclusion effect

Occurs with indirect ISE (sample mixed with diluent)

Assumes plasma samples are all 93% water and ions are in the water portion, excluding ions that may be in the 7% solid portion

Hypervolemic hyponatremia

Always hyperosmolar, due to excess H2O loss

Can be renal or extrarenal depending on Na+ urine concentration

Extrarenal-diarrhea, burns, fever, sweating

Renal-Diuresis, overhydration, diuretics

Hypervolemic hypernatremia

Gain of both water and sodium ions

Hypertonic saline IV, Na+ bicarb in hospital settings, Hyperaldosteronism and Cushing syndrome are less common

Potassium Ion

Major ICF cation

Heart and muscle function, fluid and electrolyte balance

Maintained by the kidneys

Hypokalemia-Redistribution

Extracellular K+ being shifted into cells is commonly seen as an insulin response, can be a feature of alkalosis, and/or trauma based catecholamine production

Hypokalemia-True K+ deficit

Can be either renal or extrarenal, determined by the amount of K+ lost/day in urine

Seen with metabolic alkalosis, steroid therapy, hypernatremia, diuretics, medications, vomiting

Metabolic acidosis (renal tubular acidosis)

3 types of Hyperkalemia

Can be either due to redistribution, increased intake, or increased retention

Causes of Hyperkalemia-Redistribution

Metabolic acidosis, dehydration, massive tissue hypoxia, insulin deficiency

Hyperkalemia-Retention

Hemolysis, blood transfusion, ACE inhibitors, Sickle cell, renal transplants

Hyperkalemia symptoms

Disorientation, weakness, tingling, flaccid extremity paralysis, cardiac conduction defects

Chloride Ion

Major ECF anion

H2O distribution, osmotic pressure, anion-cation balances and indicate acid base balances

Hypochloremia

Prolonged gastric secretion or vomiting, respiratory acidosis

Hyperchloremia

Dehydration, prolonged diarrhea, diabetes insipidus, overtreatment with IV saline, Respiratory alkalosis

Metabolic alkalosis chloride shift

HCO3 moves into RBCs and Cl- shifts out into plasma

Metabolic acidosis chloride shift

HCO3 moves out into plasma and Cl- into RBCs

Respiratory alkalosis chloride shift

HCO3 moves into RBCs and Cl- moves out into plasma

Respiratory acidosis chloride shift

HCO3 moves out into plasma and Cl- shifts into RBCs

Bicarbonate ion

2nd largest plasma anion fraction

Body’s primary chemical pH buffer

Why must bicarb samples be run immediately?

Uncapped tubes are susceptible to CO2 loss

2-3 mmol CO2 lost in 1 hour

Most common method of measuring bicarb

Enzymatic- measuring the decrease in absorbance at 340 nm proprtional to total CO2

Anion gap and how to calculate

Difference between serum Na+ concentration and Cl- and HCO3 concentrations

Represents negatively charged substances not routinely measured

What does the increased anion gap mean?

Metabolic acidosis

Albumin and its function

60% of total protein

Maintain colloidal osmotic pressure

Transport molecules such as bilirubin and acidic drugs to body sites

Amino acid source

Pro and anti coagulatory effects

Hypoalbuminemia causes

Catabolism of tissue damage

Inflammation

Decreased synthesis

Primary-liver disease

Secondary-decreased intake, malabsorption, malnutrition

Increase in protein loss

Hyperalbuminemia causes

Reflects dehydration, but it’s not as significant

Prealbumin (transthyretin)

Transports thyroid hormones and vitamin A

Marker for malnutrition/poor nutritional status if reduced

Marker for protein intake quality

A/G ratio

Compares albumin levels to globulin levels

If low (more A than G):

increased globulin production-multiple myeloma, autoimmune disease

decreased production of albumin-liver disease

excessive loss of albumin-nephrotic syndrome

If high (more G than A):

decreased globulin production-leukemia, genetic conditions, hypothyroidism

a1-antitrypsin

Acute phase reactant synthesized in the liver, binds to elastase to prevent destruction of lung tissue

AAT deficiency

Potential genetic defect

1-5% of COPD patients have the deficiency-less elastase to bind to lung tissue, causing early onset emphysema

cirrhosis and liver cancer

AAT surplus

Inflammation, pregnancy, estrogen therapy

Alpha-fetoprotein

peak maternal serum levels at 30 weeks

Indicates neural tube development in fetuses

High alpha-fetoprotein (16-18 weeks)

Spina bifida and anencephaly

High AFP outside of pregnancy

Germ cell cancer (testicular, ovarian, hepatocellular)

Decreased AFP in pregnancy

Indicates primary trisomy 18

Multiple of the Median calculation

Divide mother’s AFP levels by median reference value for gestational age

a1-acid glycoprotein (orsomucoid)

Major glycoprotein to increase during APR

Primary carrier of basic drugs

a1-antichymotrypsin

APR serum glycoprotein

Increases in inflammation

Decreases in asthma, COPD, liver disease

Component in Alzheimer’s amyloid plaques

Haptoglobin

a2 globulin

Primary protein that binds free hemoglobin in plasma-1% is removed from circulation to be broken down into AA and iron

Increases during APR

Most sensitive indicator of hemolysis when it decreases

Causes of increased haptoglobin

Infection, nephrotic syndrome, hepatitis

Causes of decreased haptoglobin

Hemolysis, Cirrhosis, Severe burns

Ceruloplasmin

a2

Binds to copper in plasma and partakes in plasma redox reactions

Causes of decreased Cp

Wilson’s disease-rare genetic disease with brown rings (Kayser-Fleischer rings) around the eyes

Associated with cirrhosis, hepatitis, renal tubular acidosis, neurological damage

Marked by <20 mg/dL

Also caused by liver disease, malnutrition, nephrotic syndrome

a2 Macroglobulin

One of the largest plasma proteins

Primary or secondary inhibition of enzymes in complement/inflammatory response pathways

Causes of Increased AMG

Nephrotic syndrome, liver disease, oral contraception

Causes of decreased AMG

Pancreatitis, rheumatoid arthritis, multiple myeloma

Transferrin

Beta globulin

Binds/transports iron from intestine to bone marrow, liver, spleen

Bond with iron prevents kidneys from excreting iron

Used for monitoring IDA treatment

Negative APR

Causes of increased TRF

IDA, pregnancy, oral contraceptives

Causes of decreased TRF

Inflammation, nephrotic syndrome, hemochromatosis

B2-microglobulin

beta globulin

On cell membrane of most nucleated cells, part of MHC Class I receptor

Used to assess renal tubular function in kidney transplant patients-more at risk of rejection if lower RT function

Prognostic indicator of multiple myeloma

High BMG causes

Multiple myeloma, malignant lymphoma, inflammation, kidney failure

C reactive protein

Most well known APR in clinical chem

Nonspecific inflammatory marker

More useful than erythrocyte sedimentation rate for measuring acute inflammatory response

Causes of increased CRP

MI, cancer, chronic inflammation

Complement

Beta

Cascade system of tens of glycoproteins

Fights infection through opsonization, phagocyte attraction, pore in bacterial membrane

Increases during inflammation

Other B-globulins

B-lipoproteins-carry lipids in plasma

Hemopexin-removes heme from circulation, weak APR

Fibrinogen-APR, coagulation factor

Gamma globulins

5 antibody classes

hsCRP assays

Sensitive assay to stratify MI risk based on CRP levels

Immunofixation electrophoresis

Antisera targeting proteins instead of dyes-darker bands for increased concentration

Identifies Ig class or protein fragment

What elements are sstored in the bone?

Ca (99%), PO4 (85%), and Mg (55%)

What minerals and vitamins play a part in remodeling of the skeleton?

Ca, PO4, Mg, PTH, and Vitamin D, as well as cortisol and other thyroid hormones

Calcium Ion

Mainly intracellular cation

Cofactor in muscle contraction, hormone secretion, glycogen metabolism, cell division

In ECF: Bone mineralization, coag cofactor, plasma membrane

3 Forms Ca exists in the blood

Ionized/Free: 50%

Protein-bound: 40%

Complex: 10%

Relationship between PTH and Ca

Increase of free Ca=decrease in PTH

Decrease of free Ca=increase in PTH

PTH promotes

Bone resorption by increase Ca and PO4

Conversion of stored vitamin D to active form

Ca reabsorption in kidneys

What form of calcium is best for judging the body’s Ca status

Free Ca

Most common cause of hypocalcemia

Decreased albumin, especially in hospital patients

Also seen in conditions such as hypoparathyroidism, osteomalacia, and cancers