14. Chemistry Panels Flashcards
What are the main tubes used for chemical analysis?
red top
Tigertop/serum separator
Greentop
What is the order of draw for red top, tiger top and green top?
Red top > Tiger top > Green
What does a red top and tiger top do?
Blood collected and allowed to clot for 20-30m (depending on prescene or absence of clot activator) and centrifuged for 10 m at 2000-3000 rpm to obtain SERUM
If testing can not be performed within 1hr, aliquot serum into a sterile, labelled red top tube and refrigerate/freeze to preserve
WHat is the purpose of green top tubes?
After collection, mix well and centrifuge immediately to obtain plasma
If unable to centrifuge within 1hr, refrigerate sample
for best results, remove plasma from cells before testing or sending out the sample
Transfer plasma into a labelled red top tube
What are some factors that might influence results?
hemolysis
lipemia
Icterus
How would hemolysis affect results?
occurs when blood mixed too vigorously, a small gauge needle is used, or excess alcohol is applied to the skin of the patient
Intracellular fluid from the ruptured cells will dilute the sample
intracellular components from ruptured cells may cause artificial increased in potassium, bilirubin and some enzymes including lipase
How would lipemia affect results?
occurs when patient not fasted and in some dz conditions
may be difficult to obtain results on an undiluted sample
increase risk of hemolysis
How might icterus affect results?
occurs when a patient has an excess of bilirubin in the peripheral blood
Results in a falsely decreased creatinine, cholesterol and total protein measurement
Once a sample is collected, what are some general notes to keep in mind in regards to storage and labelling?
Remove serum/plasma from cells for testing, chipping or storage
store in fridge or freeze sample for longer term storage or transport - for referred out tests, check to see what the req’s for shipping is
Do NOT freeze whole blood - only serum and plasma
A fasted sample is ideal to prod most reliable results
Samples must be labeled w/ patient and owner name, date, time of collection and sample type
Where are the majority of plasma proteins produced? WHat other systems play a role in making some proteins?
Majority produced in liver
Immune system (reticuloendothelial tissues, lymphoid tissues, plasma cells) are also responsible for making some proteins
What proteins are most commonly evaluled?
total protein, albumin, fibrinogen
What are the main functions of proteins?
sever as transport or carrier molecule for many plasma constituents
role in coagulation
hormones
buffers to help maintain acid-base balance
enzymes in biochemical reactions
maintain oncotic pressure
role in immune response to pathogens
What are protein assays not considered, but results could still be indicative of ….
Protein assays not considered to be liver function tests, results are indicative of a variety of dz, especially liver, kidney and potentially GI dz
What is total protein?
protein lvls affected by impaired hepatic synthesis, altered protein distribution, altered protein breakdown or excretion, dehydration and overhydration
What is knowing the total protein lvls useful for?
determining animals state of hydration
Dehydration > hyperproteinemia
Overhydration > hypoproteinemia
Great overall screening test for animals w/ edema, ascites, diarrhea, weight loss, hepatic or renal dz, blood clotting problems
How do we test total protein?
Refractometer
biuret method
How do we test total protein with a refractometer?
measures the refractive index of the sample, influenced by concentration of solid particles in the plasma/serum sample. most of the solid particles in the sample are proteins
fast, inexpensive and accurate
How do we test total protein doing the biuret method?
measures thr # of molecules in serum/plasma that contain more than 3 peptide bonds - simple and accurate, commonly used by analytic instruments in the lab
additional, specialized methods used in research
What is albumin?
makes up 30-50% of plasma total protein in most mammals
states of hypoproteinemia are usually due to decreased albumin lvls
What are the main functions of albumin?
binding to other molecules in the plasma (including meds)
transporting molecules thruout the body
Maintaining oncotic pressure
How does diffuse liver dz affect albumin lvls?
causes albumin lvls to fall below the reference range due to dec albumin production
What are conditions resulting in increased albumin?
dehydration
What are conditions that decrease albumin?
blood loss, overhydration, malabsorption, malnutrition and starvation
renal disease (protein losing nephropathy)
GI dz (protein losing enteropathy)
hepatic insufficiency
exudative skin dz
What are globulins?
A complex group of proteins
Alpha globulins: synthesized in the liver, carrier molecules for other proteins including HDL’s and LDL’s
Beta globulins: synthesized in the liver, include proteins responsible for iron transport, heme binding, complement, fibrin formation and lysis
Gama globulins or immunoglobulins: produced in plasma cells, Ab’s (IgG, IGE, IgA, IgM +/- IgD)
Albumin + Globulins = total protein
What is the albumin/globulin ratio?
A/G imbalance is often the first sign of a protein abnormality
can detect increased or decreased albumin or globulin lvls
Both can be reduced in equal proportions, as with hemorrhage - ratio will remain unchanged in this case
What is the A/G ratio in dogs, horses, sheep and goats?
> 1.00
Albumin > globulin
What is the A/G ratio in cattle, pigs and cats?
<1.00
Albumin < Globulin
What is fibrinogen?
Soluble protein that converts fibrin to form the matrix of blood clots
makes up 3-6% of total plasma proteins
decreased fibrinogen, as seen with hepatic insufficiency, means that the time for clot formation is prolonged or the blood will not clot at all
Fibrinogen lvls may be increased in acute inflam in lg animals and with tissue damage
What is the function of liver?
metabolism of AAs, carbs, and lipids
Synthesis of albumin, cholesterol and plasma proteins (including clotting factors)
Digestion and absorption of nutrients related to bile formation
Secretion of bile and bilirubin
Breakdown and elimination of toxins and drugs
What does the gallbladder do?
works and sits alongside liver
primary func to store bile that is produced by the liver
pathology affecting liver or gallbladder may = jaundice, clotting factors, hypoalbuminemia, hypoglycemia, hyperlipoproteinemia, hepatoencephalopathy
What are hepatobiliary assays?
no single test that can be performed to fully eval liver
dz’s of liver tend to be fairly advanced by time they are clinically apparent
only 100 tests available
What are some tests done to evaluate the liver?
lvls of molecules that liver produces and metabolizes
Bile acids - hepatic function test
Bilirubin - hepatic function test
Molecules that are released when hepatic cells are damaged or with cholestasis (impaired flow of bile)
What are the major enzymes released from damaged hepatocytes?
ALT, AST, ID, GLDH
What are the enzymes associated with cholestasis?
ALP and GGT
What is bilirubin?
Macrophages in spleen break down hemoglobin > insoluble bilirubin molecules released in process
Albumin binds to bilirubin and transports it to the liver
Hepatic cells metabolize bilirubin and it conjugates (or binds to) to glucuronide > will become component of bile
Conjugated bilirubin passes from liver into intestine where bact convert bilirubin glucuronide to urobilinogen
Urobilinogen broken down into urobilin and excreted in feces and urine, or absorbed back into the bloodstream
What amount of total bilirubin in serum in most animals is prehepatic bilirubin?
about 2/3rds
It is bound to albumin
What happens when there is an increase of unconjugated bilirubin?
When there is an increase of RBC destruction and there are problems with transport or uptake of bilirubin into the hepatocytes
What happens when there is an increase on conjugated bilirubin
increased when there is an obstruction of the bile ducts
What can an assay measure in regards to bilirubin?
Can measure total bilirubin (uncon/conjugated) as well as separately measures uncon/conjugated bilirubin
will help to determine cause of jaundice
What are bile acids/
bile acids are prod from cholesterol by hepatocytes in the liver
they aid in fat absorption and regulate cholesterol lvls
bile acids pass into the intestine via the biliary system and are stored in the gallbladder (except in horses)
Most of the bile is reabsorbed by the intestine and then processed by the liver, the rest is excreted in the feces
What are some reasons that serum bile acid lvls may be reduced?
prolonged fasting/starvation
diarrhea
malabsorptive dz’s
What might cause serum bile acids to be elevated?
When the hepatocytes, biliary or portal systems are impaired bc of
chronic hepatitis (viral, bact or fungal)
chronic cirrhosis (due to dz, drugs or toxins)
Cholestasis, portosystemic shunts (PSS)
neoplasia
What might an inc of bile acids in horses be from?
They are inc due to hepatobiliary dz and dec food intake
Is bile acids sensitive in cettle?
bile acid testing not sensitive indicator of hepatic dz in cattle
What might stimulate bile acid relase?
eating, or smelling food can release bile into the duodenum and increase in serum bile acids
How do we test for bile acid testing?
a serum sample is collected after a 12hr fast, a subsequent sample is collected 2hrs after a high fat meal is ingested
Horses: a single sample is collected
What are leakage enzymes?
enzymes that leak out of damaged hepatocytes
What are transaminases?
catalyze reactions during AA prod > found in tissues where protein breakdown occurs
Alanine transaminase (ALT)
aspartate transaminase (AST)
What are dehydrogenases?
catalyze the transfer of hydrogen during glycolysis
iditol dehydrogenase (ID)
Glutamate dehydrogenase (GLDH
What is alanine transferase?
ALT considered to be liver-specific screening test in D/C
when liver is damaged, inc ALT lvls are seen within 12hr, will peak at 24-48 hrs and will return to normal within a few weeks
For horses, ruminants, pigs and birds, the hepatocytes do not contain enough to be an ALT to be considered liver specific (ID is a better test)
ALT also found in cells of kidneys, pancreas and skeletal muscle, therefore damage to any of those organs will result in an inc in ALT
What is aspartate transaminase?
AST is present in cells of liver, RBCs, heart, skeletal muscle, kidneys and pancreas
blood AST lvls increase more slowly than ALT lvls but return to normal within a day
Most common causes of inc AST are hepatic dz, muscle inflam - strenuous exercise, IM injections or necrosis
Hemolysis - spontaneous or artifact - look at sample
Can be correlated w/ creatinine kinase (CK) to determine if muscle inflam likely to be the cause of inc ASt in a patient
What is iditol dehydrogenase?
ID especially helpful for testing liver damage in lg species like sheep, goat, swing, eq and cattle (as opposed to ALT) but ID testing often not readily available in labs
ID lvls rise quickly w/ hepatocellular damage or necrosis
this enzyme is very unstable in plasma or serum so specimens to be saved, transported or referred out must be frozen
What is glutamate dehydrogenase?
GLDH found in highest con in liver cells of cattle, sheep and goats
elated lvls are indicative of liver damage or necrossis in cattle and sheep
What are some enzymes indicative of cholestasis?
plasma and serum lvls of some enzymes are predictably elevated in
cholestasis (impaired flow in bile)
Metabolic defects in liver cells
with use of certain meds
due to action of certain hormones (ex. corticosteroids, thyroid hormones)
What is alkaline phosphatase?
ALP is enzyme found in osteoblasts in bone, chrondroblasts in cartilage, intestine, placenta and liver
Inc ALP in lg breed pups common during bone development; older anims the bones no grow so inc lvl of ALP more common w/ cholestasis
Steroid induction in dogs
ALP testing not useful in cattle + sheep
Most often used for D/C
What is gamma glutamyltransferase?
Primary sounce of GGT is liver in most animals
Blood GGT lvls higher in cows, eq, sheep, goat than in D/C
GGT found in several other organs including renal, biliary and mammary epithelium
elevated GGT lvls suggestive of liver dz, especially obstructive liver dz
When evaluating liver enzymes, what should they be correlated with?
results are associated w. other organs - correlating glucose (pancease and liver results), correlating AST and CK (muscle) results
hx and clin signs
signalment
What is the kidney’s function?
conserve and elim h2o and electrolytes
conserve and elim hydrogen and maintain pH balance
conserve nutrients: glucose and protein
elim toxins and end products of nitrogen metabolism: urea and creatinine
What do kidney’s produce?
Renin: an enzyme for controlling blood pressure
Erythropoietin
Prostaglandins: fatty acids that stim smooth muscle contraction
What are some other system functions of kidney’s besides conserve and eliminate water and waste?
blood pressure regulation, regulation of acid secretion in the stomach, regulation of body temp and platelet aggregation, activation of vitamin D and controlling inflammation
What is the renal physiology?
Blood enters kidney via renal arteries into glomerulus of nephron
Almost all water and sm particles pass into collecting tubules
Each nephron has parts that reabsorb or secrete certain solutes; the amount of solute that kidney is reabsorbed is pre-decided > renal threshold
Approx. 99% of water is reabsorbed by kidney, remaining is urine
Tests to eval kidney func are performed on urine and blood
What is azotemia? (NEED TO KNOW)
An increase in BUN and creatinine
Rarely is just one elevated out of the two
What is uremia?
An increase in BUN and creatinine but is now severe enough to cause animal to feel ill.
They will be dehydrated, inappetent and lethargic
May be V/D, have “uremic” oral and or/gastric ulcers and central nervous dysfunction
seen w/ advanced renal disease
How do we classify azotemia?
Pre-renal azotemia: underlyding cause of azotemia is occurring “before” kidney
Renal azotemia: Occuring within the kidney
Post-renal azotemia: Occuring after the kidney
What is pre-renal azotemia?
dehydration most common underlying cause
PVC and TP may be mildly elevated
USG is elevated - urine is well concentrated bc animals kidneys are functioning normally and are conserving water
What is renal azotemia?
Can be due to renal failure, congenital disorders or pyelonephritis
Renal failure can be classified as acute or chronic
PCV and TP may be elevated if the animal is dehydrated (often are, especially as dz progresses)
Animal may become anemic with end stage, chronic renal disease due to dec prod of EPO
USG will be dec (urine will be dilute)
What is the difference between acute and chronic renal azotemia?
Acute: often very severe, sudden onset, often (but not always) younger animals; may be associated w/ known toxin exposure
Chronic: gradual decrease in renal function and onset of clinical signs
What is post renal azotemia?
An obstruction in the ureter, neck of the bladder or urethra can cause a post renal azotemia
These animals are often dehydrated so PCV and TP will likely be elevated
USG will be elevated (urine is well concentrated)
What is BUN?
Blood urea nitrogen, the principal end-product of AA breakdown in mammals
used to eval kidney function due to kidney’s ability to filter urea from blood
What normaly happens with BUN and kidney excretion?
All urea passes thru glomerulus into renal tubules
about half of urea is reabsorbed into the bloodstream and other half is excreted in the urine
What abnormally happens with BUN and renal excretion?
urea is not transported into renal tubules as efficiently
When blood exits the kidney back into circulation, there is an increased concentration of urea
What might an increased BUN mean?
does not guarantee an absolute diagnosis of kidney disease
What are some non-renal causes of increased BUN include?
dehydration - urea is insoluble, high volumes of water are needed for its excretion in urine
High protein diets or strenuous exercise - leads to an increase in protein breakdown
How is BUN evaluated?
using an automated analyzer or w/ semi-qualitative dipstick
What serum creatinine?
creatinine is formed from creatine (component of muscle) as part of muscle metabolism
During muscle metabolism, creatinine diffuses out of muscle cells into body fluids and blood
creatinine lvls are influences by animal’s muscle mass
What typically happens with serum creatinine in the body?
normally, blood creatinine active filtered out of blood and into renal tubules - any condition that alters glomerular filtration rate (GFR) will alter the creatinine concentration in plasma
What needs to happen before blood creatinine lvls increase
Renal function has to be reduced by ~75% b4 blood creatinine lvls inc - creatinine alone is also not an accurate indicator of renal function
