Term
| Define plasma and list its components. |
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Definition
| the fluid portion of unclotted blood. Composed of 90% water and 10% dissolved constituents such as proteins, carbohydrates, vitamins, etc |
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Term
| . Define serum. How does it differ from plasma? |
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Definition
| the fluid portion of clotted blood. During the clotting process, the soluble fibrinogen in plasma is converted to an insoluble fibrin clot matrix. When blood clots, the fluid that is squeezed out around the cellular clot is serum. Serum should NOT be anticoagulated or stirred, since clotting is part of the process to remove fibrinogen from the sample. |
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Term
| What are the 2 most commonly used anticoagulants? |
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Definition
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Term
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Definition
• Recent food ingestion: This will produce a post-prandial lipemia. Lipemia may affect the analytical methods used to measure certain plasma constituents, thus producing invalid results. Post-prandial lipemia can be avoided by appropriate sample collection, namely after a 12-hour fast. Indeed, fasting lipemia is good evidence for altered lipid metabolism secondary to disease. What are some examples of diseases that produce a fasting lipemia?
Recent food ingestion may affect the concentration of certain plasma constituents independently of lipemia, e.g. glucose. This effect is distinctly species dependent due to differences in food metabolism (e.g. non-ruminant versus ruminant). |
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Term
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Definition
May result when
- a blood sample is drawn into a moist syringe
- mixed too vigorously after collection
- forced through a needle when transferred to a tube
- frozen as a whole blood sample
- when excess alcohol is used to clean the skin and not allowed to dry before collecting blood |
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Term
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Definition
- can greatly alter makeup of a serum or plasma sample
- fluid from ruptured cells can dilute the sample, resulting in falsely lower concentration of constituents than are actually present in the animal
-certain constituents normally not found in high concentrations in serum or plasma escape from ruptured blood cells, causing falsely elevated concentrations in the sample.
- may elevate certain levels of K, organic phosphorus, and certain enzymes in the blood
- also interferes w/ lipase, activity, and bilirubin determinations
- therefore plasma or serum is frequently the preferred sample over whole blood and serum is preferred over plasma |
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Term
| Why should an animal be fasted prior to collecting a blood sample (if possible)? |
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Definition
Recent food ingestion: This will produce a post-prandial lipemia. Lipemia may affect the analytical methods used to measure certain plasma constituents, thus producing invalid results. Post-prandial lipemia can be avoided by appropriate sample collection, namely after a 12-hour fast. Indeed, fasting lipemia is good evidence for altered lipid metabolism secondary to disease.
False values may be produced, incl glucose, urea and lipase |
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Term
| . Define “post-prandial”. |
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Definition
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Term
| What are the controllable or patient variables that may affect blood chemistry results? |
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Definition
- proper sample collection, prep and handling by vet/tech
- recent food ingestion
- stress (secondary to handling or underlying dz)
- exercise (effect dependent on both the species and intensity of exercise – in general pre-exercise samples)
- Drugs (1. physiological (in vivo) effects of the drug or metabolites on the analyte to be measured, 2. in vitro effects due to some physical or chemical |
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Term
| . What are the pre-analytical variables that may affect the blood chemistry test results? |
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Definition
- these are the most important and common sources of error in analysis and often overlooked when interpreting test data
- include biological (inherent to pt and cannot be controlled) and non-biological (sample) factors
Biological
- species
- breed
- age
- gender
Non-biological (sample) factors
- clean venipuncture
- anticoagulant – heparinized plasma or serum no anticoagulant
- separate serum or plasma from cells as soon as possible, allow to clot (for serum) and centrifuge to separate. The serum/plasma should be separated from cells and placed into a new (no anticoagulant) tube
- may use serum separator tube but serum should still be withdrawn and placed into new clot tube
- labeling
- storage |
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Term
| . How are “Reference Values” developed? |
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Definition
| Assay samples from a significant # of clinically normal animals, at least 20 - 100 |
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Term
| What factors may cause variations in reference ranges? |
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Definition
- Variety of breeds/species
- Gender/status
- Environment, incl husbandry and nutrition
- climate |
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Term
| Why should the lab be informed of any medications that the animal is on? |
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Definition
There are a number of different methodology-related drug interferences that may bias results. One of the most common drug interferences seen in veterinary medicine is the artefactual elevation of chloride values in samples from dogs on bromide therapy (an anticonvulsant). It is always wise to inform the laboratory of any medications in a particular animal, so that drug influences on chemistry tests can be minimized (but usually not eliminated).
• Drugs: The technique of drug administration, e.g. intramuscular, can directly affect analyte results. Which analytes may be affected by intramuscular drug administration?
Drugs can also interfere with measurement of the analyte. Drug interference can be grouped into two general categories:
1)) Physiological (in vivo) effects of the drug or metabolites on the analyte to be measured
2) In vitro effects due to some physical or chemical property of the drug or its metabolites, which interfere with the actual assay procedure.
An example of therapeutic agents that produce marked assay interference is hemoglobin-based oxygen carriers (HBOC), such as Oxyglobin. Oxyglobin is polymerized hemoglobin of bovine origin and is, consequently, dark red. Administration of oxyglobin for treatment of anemia causes the equivalent of hemolyzed serum/plasma in the animal due to the inherent color of the compound. This can be seen vividly in the image below; the plasma sample on the left is pre-, that on the right, post-Oxyglobin, administration.
This markedly interferes with both hematologic, chemistry and urinalysis results. Interference with chemistry tests is dependent on the method and instrumentation used. According to the manafacturer of Oxyglobin, valid results are obtained for the following analytes in dogs with Hitachi chemistry analyzers: electrolytes, BUN, CK, glucose, ALT, AST and calcium. Reagent manafacturers are working hard to produce new methods to compensate for or eliminate the interference from HBOCs, so it is likely that, in future, more accurate chemistry measurements will be obtained in animals administered HBOCs. This emphasizes the importance of collecting blood samples from anemic animals before administration of HBOCs to minimize the effect on laboratory results.
Whenever possible, the laboratory should be informed of any drug medication so steps can be taken to minimize the effect of the drug on assay performance. Unfortunately, little is known in veterinary medicine about the effect of drugs on both the animal or analytical techniques, with some notable exceptions (can you think of such an exception?). Therefore, any abnormal chemistry results should be interpreted with full knowledge of the animal's medication history |
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Term
| Why is it important to separate the serum or plasma from cells and keep the sample cool or frozen if there is to be a delay in getting the sample to the diagnostic lab |
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Definition
| since the RBCs will continue to undergo some metabolic processes |
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Term
| 23. How can lipemia, hemolysis, icterus, and drugs interfere with the test results? |
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Definition
Lipemia
- increased light scattering
- decreased volume displacement
- hemolysis
Hemolysis
- increased release of analytes
- altered release of enzymes
- rxn inhibition
- increased OD (absorbance)
- release of water
Icterus
- spectral interference
- chemical interaction
Drugs
- rxn interference |
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Term
| 1. Where are plasma proteins produced? |
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Definition
- Produced primarily by the liver and the immune system
- Consisting of reticuloendothelial tissues, lymphoid tissues, and plasma cells
- Proteins have many fxns in the body and alterations in plasma protein concentrations occur in a variety of dz conditions, esp dz of liver/kidneys |
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Term
| List the 3 plasma protein assays performed in veterinary medicine? |
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Definition
- total protein
total plasma protein measurements include fibrinogen values, while total serum protein measurements measure all the protein fractions except fibrinogen
TP concentration may be affected by altered hepatic syntheis, altered protein distribution, and altered protein breakdown or excretion as well as dehydration and overhydration
Esp valuable in determining state of hydration (dehydrated = elevated TP/hyperproteinemia, overhydrated = decreased TP/hypoproteinemia)
Also useful as screening tests for pts w/ edema, ascites, diarrhea, wt loss, hepatic and renal dz and blood clotting problems
- albumin –
one of the most important proteins in plasma or serum
makes up 35 – 50% of the total plasma protein in most animals
any significant state of hypoproteinemia is most likely caused by albumin loss
hepatocytes synthesize albumin, any diffuse liver dz may result in decreased albumin synthesis
renal dz, dietary intake, and intestinal protein absorption also may influence the plasma albumin level
albumin is the major binding and transport protein in the blood and is resp for maint osmotic pressure of plasma
- globulins |
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Term
| . What are the functions of plasma proteins? |
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Definition
- helping form the structural matrix of all cells, organs, and tissues
- maint osmotic pressure
- serving as enzymes for biochemical rxn
- acting as buffers in acid-base balance
- serving as hormones
- fxning in blood coagulation
- defending the body against pathogenic microorganisms
- serving as transport/carrier molecules for most constituents of plasma |
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Term
| . What are the 2 primary methods to measure total protein? |
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Definition
- refractometric method
> measures the refractive index of serum or plasma with a refractometer
> refractive index is a fxn of the concentration of solid particles in the sample
> in plasma, the primary solids are the proteins
> good screening test because fast, inexpensive and accurate
- biuret photometric method
> measures the # of molecules containing more than 3 peptide bonds in serum or plasma
>commonly used in analytic instruments in the lab
> simple method, accurate |
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Term
| What is the difference between total plasma protein and total serum protein? |
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Definition
| in plasma, the primary solids are the proteins |
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Term
| What is albumin and where is it produced? |
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Definition
one of the most important proteins in plasma or serum
makes up 35 – 50% of the total plasma protein in most animals
any significant state of hypoproteinemia is most likely caused by albumin loss
hepatocytes synthesize albumin, any diffuse liver dz may result in decreased albumin synthesis
renal dz, dietary intake, and intestinal protein absorption also may influence the plasma albumin level
albumin is the major binding and transport protein in the blood and is resp for maint osmotic pressure of plasma |
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Term
| What are globulins and where are they produced? |
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Definition
| alpha globulins are synthesized in the liver and primarily transport and bind proteins |
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Term
| What is the difference between total plasma protein and total serum protein? |
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Definition
- no fibrinogen is found in serum because it is removed from plasma during the clotting process
in plasma, the primary solids are the proteins |
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Term
| . What is fibrinogen, where is it produced? What sample is used to measure fibrinogen levels? Why? |
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Definition
- it is the precursor of fibrin, the insoluble protein that forms the matrix of blood clots and is one of the factors needed for clot formation
- is synthesized by hepatocytes
- if fibrinogen levels are decreased, blood does not form a stable clot or does not clot at all
- fibrinogen makes up 3 – 6% of the total plasma protein
- no fibrinogen is found in serum because it is removed from plasma during the clotting process therefore only plasma must be used
- acute inflammation or tissue damage may elevate fibrinogen levels
- plasma w/ EDTA is preferred, heparinized plasma may yield falsely low results |
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Term
| . What is the largest internal organ? |
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Definition
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Term
| . List the functions of the liver. |
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Definition
Many fxns, including
- metabolism of amino acids, carbs, and lipids
- synthesis of albumin, cholesterol, plasma proteins, and clotting factors
- digestion and absorption of nutrients related to bile formation
- secretion of bilirubin or bile
- elimination, such as detoxification of toxins and catabolism of certain drugs
- these fxns are run by exzymatic rxns |
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Term
| What are the enzymes associated with hepatocellular damage? |
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Definition
“leakage enzymes” (w/ this type of liver dz, the hepatocytes are damaged and enzymes leak into the blood, causing a detectable rise in blood levels of enzymes associated w/ liver cells)
- ALT – alanine aminotransferase
- AST – aspartate aminotransferase
- SDH – sorbitol dehydrogenase
- GLDH – glutamate dehydrogenase |
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Term
| . How does hemolysis and lipemia affect the level of ALT and AST? |
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Definition
| Hemolysis increases AST, sample should be checked for hemolysis if elevated AST |
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Term
| What are the enzymes associated with cholestasis |
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Definition
- AP – alkaline phosphatase
- GGT – gamma glutamyltransferase |
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Term
| In what tissues can AP be found? |
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Definition
- Present as isoenzymes in many tissues
- particularly osteoblasts in bone
- chondroblasts in cartilage, intestine, and placenta
- cells of the hepatobiliary system in the liver
- isoenzymes of AP tend to remain in circulation for ~ 2 – 3 days, w/ the exception of the intestinal isoenzyme that circulates for just a few hrs |
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Term
| List the tests used to determine how well the liver is functioning and what each test measures. |
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Definition
bilirubin
– assayed to deterimine the cause of jaundice, eval liver fxn, and check the patency of bile ducts.
– Blood levels of conjugated (direct) bilirubin are elevated with hepatocellular damage or bile duct injury or obstruction
– Blood levels of unconjugated (indirect) bilirubin are elevated w/ excessive erythrocyte destruction or defects in the transport mechanism that allow bilirubin to enter hepatocytes for conjugation.
Bile Acids
- serve many fxns
- aid in fat absorption (enabling the formation of micelles in a GI system)
- modulate cholesterol levels by bile acid synthesis
- synthesized by hepatocytes from cholesterol and are conjugated with glycine or taurine
- postprandial serum bile acid (SBA) concentrations are higher than fasting concentrations
- any process that impairs the hepatocellular, biliary, or portal enterohepatic circulation of bile acids results in elevated SBA levels
- the great advantage of SBA determinations as a liver fxn test is that they elevate the major autonomic component of the hepatobiliary system and are stable in vitro
- important to draw after 12 hours fasting, then 2 hrs post prandial. Prolonged fasting and/or diarrhea can decrease bile acids
Cholesterol
- plasma lipoprotein produced primarily in the liver, as well as ingested in food.
- Hyperlipidemia is often secondary to other conditions (choleostasis, DM, hepatic lipidosis, hypothyroidism, hyperadrenocorticism, acute necrotizing pancreatitis, nephrotic syndrome, corticosteroid admin)
- Sometimes used as a screening test for hypothyroidism
Others not commonly performed
Dye Excretion Tests
Ammonia Tolerance Tests
Caffeine clearance tests |
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Term
| What are the functions of bile acids? Where are they produced? |
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Definition
- serve many fxns
- aid in fat absorption (enabling the formation of micelles in a GI system)
- modulate cholesterol levels by bile acid synthesis
- synthesized by hepatocytes from cholesterol and are conjugated with glycine or taurine
- postprandial serum bile acid (SBA) concentrations are higher than fasting concentrations
- any process that impairs the hepatocellular, biliary, or portal enterohepatic circulation of bile acids results in elevated SBA levels
- the great advantage of SBA determinations as a liver fxn test is that they elevate the major autonomic component of the hepatobiliary system and are stable in vitro
- important to draw after 12 hours fasting, then 2 hrs post prandial. Prolonged fasting and/or diarrhea can decrease bile acids |
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Term
| Why does an animal need to be fasted prior to drawing a sample for a bile acid level? |
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Definition
A fasting sample is needed to compare to the postprandial level. The amt of food used with this assay is important, as lipemia can adversely affect the bile acids results and you should avoid foods with low-fat and low-protein concentrations.
Animals less than 5 kg – at least 2 tsp food
Larger animals - ~ 2/4 can of food |
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Term
| What is the ammonia tolerance test useful for? What sample is used to measure ammonia levels? |
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Definition
- ammonia is produced by enteric microflora and during amino acid metabolism and transported to the liver through the portal circulation
- enzymes in the liver convert the ammonia to urea for excretion
- any condition that reduces the uptake of ammonia or conversion to urea can lead to increased plasma ammonia concentration.
- Samples collected in ammonia-free heparin and blood centrifuged immed.
- Plasma placed on ice and analyzed w/in 30 min of collection or frozen at 220 C
- Ammonia levels stable in frozen plasma for a few days
- Whole blood cannot be tested because its ammonia content increases w/ storage |
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Term
| List the functions of the kidneys? |
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Definition
- to conserve water and electrolytes in times of a neg balance
- increase water and electrolyte elimination in times of a positive balance
- excrete or conserve hydrogen ions to maintain blood pH w/in normal limits
- conserve nutrients, such as glucose and proteins
- remove the end products of nitrogen metabolism, such as urea, creatinine, and allantoin, so that blood levels of these end products remain low
- produce rennin (an enzyme involved in controlling blood pressure), erythropoietin (a hormone necessary for erythrocyte production) and prostoglandins (fatty acids used to stimulate contractility of uterine and other smooth muscle, lower blood pressure, regulate acid secretion in the stomach, regulate body temp and platelet aggregation, and control inflammation)
- aid in vit D activation |
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Term
| 2. What does BUN stand for? What is it used to evaluate? |
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Definition
BUN = Blood Urea Nitrogen
Evaluates kidney fxn on the basis of the ability of the kidney to remove nitrogenous waste (urea) from blood. Under normal conditions, all urea passes through the glomerulus and enters the renal tubules. Approx ½ of the urea is reabsorbed in the tubules and the remainder excreted in the urine. If the kidney is not functioning properly, sufficient urea is not removed from the plasma, leading to increased BUN levels |
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Term
| . Approximately how much of the kidney tissue must be nonfunctional before blood creatinine and BUN rises? |
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Definition
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Term
| How does a high protein diet affect BUN and creatinine? |
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Definition
| High protein diets and strenuous exercise may cause an elevated BUN because of increased amino acid breakdown, not because of decreased glomerulur filtration |
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Term
| List the causes of increased BUN. |
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Definition
- if the kidney is not functioning properly, sufficient urea is not removed from the plasma, leading to increased BUN levels
- contamination of the blood sample with urease-producing bacteria (e.g. Staphylococcus aureus, Proteus spp., and Klebsiella spp.) may result in decomposition of urea and subsequently decreased BUN levels. To prevent this, analysis should be completed w/in several hrs of collection or the sample should be refrigerated
- Dehydration results in increased retention of urea in the blood (azotemia)
- High-protein diets and strenuous exercise may cause an elevated BUN level because of increased amino acid breakdown, not because of decreased glomerular filtration. |
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Term
| What contaminant can result in a decreased BUN level and how can this be prevented? |
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Definition
- contamination of the blood sample with urease-producing bacteria (e.g. Staphylococcus aureus, Proteus spp., and Klebsiella spp.) may result in decomposition of urea and subsequently decreased BUN levels. To prevent this, analysis should be completed w/in several hrs of collection or the sample should be refrigerated
Causes of increased UN
Increased protein catabolism: Fever, burns, corticosteroid administration, starvation, exercise.
Increased protein digestion: Hemorrhage into the gastrointestinal system, high protein diets.
Decreased GFR: Due to pre-renal, renal or post-renal causes.
Note that UN will be increased with a normal creatinine in the following situations:
Increased production of urea, e.g. protein catabolism.
Early prerenal azotemia (most causes of a high UN in horses and ruminants are due to prerenal causes).
Artefactual depression of creatinine, e.g. severe icterus. |
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Term
| Concentrations of UN are dependent upon |
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Definition
• Hepatic urea production: The rate of urea production is dependent on hepatic function and digestion and catabolism of protein, i.e. urea formation is decreased in liver disease (e.g. portosystemic shunts) and increased with protein catabolism or increased protein digestion in the intestine.
• Renal tubular flow rate: Urea is freely filtered through the glomerulus and passively diffuses out of the tubules at a rate dependent on flow rate through the tubules; the remainder of the filtered urea is excreted in urine. At high flow rates, approximately 40% of filtered urea is reabsorbed. At low flow rates, as happens in hypovolemic individuals, approximately 60% of filtered urea is reabsorbed and added back to the blood urea concentration. This explains the high UN levels seen with decreased GFR of any cause. |
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Term
| Creatinine: Where is this produced? |
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Definition
- Creatinine is formed from creatine, which is found in skeletal muscle, as part of muscle metabolism.
- diffuses out of the muscle cell and into most body fluids, incl blood
- if physical activity remains constant, the amt of creatinine metabolized to creatinine remains constant and the blood level of creatinine remains constant
- the total amt of creatinine is a fxn of the pt’s total mass
- under normal conditions, all serum creatinine is filtered through the glomeruli and eliminated in urine
- any condition that alters the glomerular filtration rate (GRF) will alter the serum creatinine levels |
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Term
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Definition
| increased retention of urea in the blood |
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Term
| a few conditions that can cause abnormal BUN and creatinine levels: |
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Definition
• Dehydration
• Kidney infection
• Kidney failure
• Toxic injury to the kidneys
• Urinary blockage
• Shock
• Severe heart disease
• Muscle wasting or severe weight loss |
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Term
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Definition
| 1.Production of abnormally large volumes of dilute urine |
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Term
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Definition
| o ADH – antidiuretic hormone - hormone secreted by the posterior pituitary gland (trade name Pitressin) and also by nerve endings in the hypothalamus; affects blood pressure by stimulating capillary muscles and reduces urine flow by affecting reabsorption of water by kidney tubules |
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Term
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Definition
| drinking large amounts of water |
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Term
| What is the water-deprivation test used for? |
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Definition
- used to test for lack of endogenous ADH or unresponsive nephrons
- basis is to dehydrate the pt safely until a definite stimulus exists for endogenous ADH release (usually at ~ 5% body wt loss. End point may vary. Pts dehydrate at different rates and must be monitored for wt loss, clinical signs of dehydration, and increased urine osmolarity or specific gravity
- at end point, kidney should be under endocrine orders to concentrate urine
- continued diuresis and dilute urine indicate lack of endogenous ADH or unresponsive nephrons
- in dogs w/ kidney failure, this unresponsiveness precedes azotemia
- contraindications include: dehydration and azotemia. Dehydrated pts risk hypovolemia and shock, already have max ADH release, if could concentrate, they would. Test then useless/dangerous, esp w/ diabetes insipidus or neurogenic diabetes insipidus. If azotemic, already attests to kidney dysfunction |
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Term
| What is the Urine P/C Ratio? |
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Definition
- used as a quantitative assessment of renal proteinuria
- in the absence of inflammatory cells in the urine, proteinurua indicates glomerular dz
- based on the concept that the tubular concentration of urine increases both the urinary protein and creatinine concentrations equally |
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Term
| How to perform a Urine P/C ratio |
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Definition
- 5 – 10 ml of urine collected between 10am – 2pm, preferably by cysto
- sample kept at 4 C or stored at 20 C
- centrifuge, use supernatant |
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Term
| What is the value for healthy dogs? |
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Definition
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Term
| What causes a U P/C of 1-5? |
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Definition
| Urine P/C between 1 and 5 may have prerenal (hyperglobulinemia, hemoglobinemia, myoglobinemia) or functional (exercise, fever, hypertension) origin |
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Term
| What causes a U P/C greater than 5? |
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Definition
| Urine P/C greater than 5 is caused by renal failure |
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