Clinical Chemistry Flashcards
Hemolysis
The destruction of erythrocytes
Icterus
yellowing of the skin and the whites of the eyes caused by an accumulation of bile pigment (bilirubin) in the blood
Also called jaundice
Lipemia
The presence of fatty material in plasma or serum
Plasma
The fluid portion of blood
Reference range
Normal values
Serum
The fluid portion of blood after it has clotted
It does not contain cells or coagulation proteins
Describe proper sample processing for plasma samples
- Collect a blood sample in an appropriate container
- Mix the container with a gentle rocking motion
- Make sure the container is covered to prevent evaporation during centrifugation
- Centrifuge at 2000-3000 rpm for 10 minutes
- Carefully remove the fluid plasma layer from the bottom layer of cells with a capillary pipette
- Transfer the plasma to properly labeled container
- Process the sample immediately or refrigerate or freeze as needed
Describe proper sample processing for serum samples.
- Collect a whole blood sample in a container that contains no anticoagulant
- Allow the blood to clot in its original container at room temp for 20-30 mins
- Gently separate the clot from the container by running a wooden applicator stick around the wall between the clot and the wall
- Cover the sample and centrifuge it at 2000-3000 rpm for 10 minutes
- Remove the serum from the clot with a capillary pipette
- Transfer the serum to an appropriately labeled container
- Refrigerate or freeze the sample as appropriate
Discuss the effects of sample quality in test results.
Lipemia: light scattering, volume displacement, or hemolysis
Hemolysis/blood substitutes: release of analytes, release of enzymes, reaction inhibition, increased optical density(absorbance), release of water
Icterus: spectral interference, chemical interaction
Hyperproteinemia: hyperviscosity, analyte binding, volume displacement
Medications: reaction interference
List the common causes of sample compromise.
Lipemia
Hemolysis/blood substitutes
Icterus
Hyperproteinemia
Medications
Describe how to minimize causes of hemolysis
Use a completely dry syringe
Remove the needle from the syringe before transferring the blood
Too much alcohol on the injection site
Describe how to minimize the causes of chemical contamination.
Tubes need to be chemically pure, and detergents completely rinsed from reusable tubes
Describe how to minimize the causes of improper labeling
ALWAYS label the tube with the date, time of collection, patient’s ID number or name
ALWAYS DOUBLE CHECK SAMPLE IDENTIFICATION
Describe how to minimize the causes of improper sample handling.
All chemical measurements should be completed within 1 hour of sample collection or properly handled and stored
Samples cannot become too warm
If a sample is frozen, use gentle inversion after thawing
Describe how to minimize the causes of patient influences
Try to obtain sample from fasted animal
Water restriction is not necessary
Beer’s law
A principle that describes the relationship between light absorbance, transmission, and the concentration of a substance in a solution
End point assay
A chemical reaction that proceeds to a stable end point
Ion-selective electrode
Kinetic assay
A chemical test that measures the rate of change of a substance in the test system
Optical density
The degree to which light is transmitted through a medium
Reflectometer
an instrument for measuring quantities associated with reflection
Spectrophotometer
A piece of equipment designed to measure the amount of light that is transmitted through a solution
Describe the principle of refractometry
based on a transparent or translucent material’s ability to refract and shift light, also known as its refractive index
Describe the principle of photometry
to measure the intensity of light by converting light into electricity
Differentiate between kinetic and end point assays
End-point essays form a stable product, while kinetic assays are more volatile
Kinetic assays use enzymes as reagents or are designed to measure enzyme concentrations
Kinetic assays are evaluated by measuring the difference in color changed at specific times after the reaction begins, while end-point assays use either a one-point calibration method or a standard curb to provide results
List the features and benefits of dry system analyzers.
Include reagent-impregnated slides, pads, or cartridges
Most use reflectance assays
Have higher costs
Do not require reagent handling performing single tests is pretty simple
Can allow for loading large numbers of slides to minimize the time required to prepare the analyzer
List the features and benefits of liquid system analyzers.
Use a lyophilized reagent or an already prepared liquid reagent
Rotor-based systems tend to be quite accurate
More cost-effective but cannot run single tests
All can be integrated into a software system
List the features and benefits of dedicated-use system analyzers.
Available for certain tests
Utilize electrochemical technology
Can be used if only a single test is requested or emergency situations
Acute-phase proteins
Proteins, including serum amyloid A and C-reactive protein, that are produced by hepatocytes immediately following injury or inflammation
Alanine transaminase
Cytoplasmic enzyme of hepatocytes released when hepatocytes are damaged
Albumin
A group of plasma proteins that comprises the majority of protein in plasma
Alkaline phosphatase
A group of enzymes that functions at an alkaline pH and catalyzes the reactions of organic phosphates
Aspartate transaminase
An enzyme that is present in body serum and in certain body tissues that catalyzes the transfer of an amino group from aspartic acid to alpha-ketoglutaric acid, thereby forming glutamic acid and oxaloacetic
Bile acids
A group of compounds that are synthesized by hepatocytes from cholesterol that help with fat absorption
Bilirubin
An insoluble pigment derived from the breakdown of hemoglobin, which is processed by hepatocytes
Cholesterol
A plasma lipoprotein that is produced primarily in the liver as well as ingested in food
Used in the synthesis of bile acids
Conjugated bilirubin
Bilirubin that has been taken up by the liver cells and conjugated to form the water-soluble compound bilirubin diglucuronide
Gamma glutamyltransferase
An intracellular enzyme found in high concentrations in liver, pancreatic, and renal tubular cells
Globulins
A complex group of plasma proteins that have been designated as alpha, beta, or gamma
Include immunoglobulins, complement, and transferrin
Glutamate dehydrogenase
A mitochondrial-bound enzyme that is found in high concentrations in the hepatocytes of cattle, sheep, and goats
Hepatoencephalopathy
Severe hepatic insufficiency that may induce a syndrome of excitability, tremor, compulsive walking, head pressing, and apparemt blindness, followed by coma and convulsions
Hyperlipoproteinemia
A condition characterized by excess lipids in the blood
Also called hyperlipidemia and hyperlipemia
Hyperproteinemia
An increased protein level in the blood
Hypoalbuminemia
A decrease in the circulating levels of albumin in the blood
Hypoglycemia
A decreased plasma glucose level
Hypoproteinemia
A condition characterized by an abnormally low level of protein in the blood
Iditol dehydrogenase
An enzyme of the oxidoreductase class that catalyzes the oxidation of l-iditol to l-fructose
Occurs in significant quantities only in the liver, and its increased activity in serum is used as an indicator of parenchymal liver damage
Jaundice
A condition characterized by hyperbilirubinemia and the deposition of bile pigments in the skin, mucous membranes, and sclera
Protein
List the potential causes of alterations in serum proteins.
Disease conditions such as liver and kidney
Age-related changes
Describe the commonly performed tests to measure total protein and albumin.
Fibrinogen values
Total protein is usually measured with a Refractometer
Most common test for albumin is dye-binding assay
Describe the common method for determining globulin concentration.
Direct measurement of globulin isn’t usually performed
Globulin concentration is calculated by subtracting the albumin concentration from the total serum protein
List the commonly performed tests for the evaluation of the hepatobility system.
Bile acids test
Enzymes analyses
Phosphatases
Transferases
Dehydrogenases
Describe the metabolism of bilirubin.
1) production
2) uptake by the hepatocyte
3) conjugation
4) excretion into bile ducts
5) delivery to the intestine
Differentiate between conjugated and unconjugated bilirubin.
Conjugated bilirubin is not reabsorbed from the proximal intestine as mentioned above; in comparison
unconjugated bilirubin is partially reabsorbed across the lipid membrane of the small intestinal epithelium and undergoes enterohepatic circulation
List the leakage enzymes.
Alanine transaminase (ALT)
Aspartate transaminase (AST)
Iditol dehydrogenase (ID)
Glutamate dehydrogenase (GLDH)
Explain the significance of altered enzyme activity.
Temperature
pH
Substrate concentration
Describe the circulation of bile acids and the significance of altered bile activity.
Bile acids are released when the gallbladder contracts in association with feeding. Most bile acids enter the intestinal tract, where they participate in fat absorption. Some bile acids are then excreted with the feces, and some are absorbed through the portal circulation.