Clinical Biochemistry Flashcards
1
Q
define clinical biochemistry
A
clinical analysis of body fluids for the diagnosis, therapy and prevention of diseases
2
Q
what can be sampled for biochemistry?
A
usually serum/plasma but can be urine and other body fluids (e.g. pleural fluid)
3
Q
what body systems/parameters does a typical biochemistry panel include?
A
liver kidney proteins electrolytes glucose lipids
4
Q
what are panels separated into?
A
organ or system
5
Q
what liver parameters are typically assessed on a biochemistry panel?
A
ALT, AST, GLDH, ALP, GGT, Bilirubin, bile acids
6
Q
what liver parameters demonstrate liver damage?
A
hepatocellular damage/ leakage enzymes - ALT, AST, GLDH
7
Q
what level of liver damage does ALT show?
A
mild
8
Q
what level of liver damage does AST show?
A
necrosis
9
Q
what liver parameters demonstrate bile accumulation?
A
cholestatic enzymes - ALP, GGT
10
Q
what substances can be measured on a biochemistry panel that are conjugated and excreted by the liver?
A
bilirubin
bile acids
11
Q
what are the main components assessed when looking at the liver?
A
enzymes and function markers
12
Q
levels of what substances produced in the liver are tested on a biochemistry panel?
A
cholesterol, urea, albumin, coagulation factors
13
Q
what are liver parameters measured in?
A
level of increase above the reference interval (e.g. 10x)
14
Q
what enzyme level can be elevated in dogs without cholestasis?
A
ALP is increased by steroids and phenobarbital
15
Q
what can AST levels be increased by as well as liver damage?
A
muscle damage
16
Q
what is measured to assess kidney function?
A
urea
creatinine
17
Q
what is measured to assess protein levels?
A
TP, albumin
18
Q
what is measured to assess electrolyte levels?
A
Na, K, Cl, Ca, PO4
19
Q
what is measured to check blood sugar levels?
A
glucose
20
Q
what is measured to assess lipid levels?
A
triglycerides
cholesterol
21
Q
what does quality control ensure?
A
results are reliable
22
Q
what should be involved in ensuring quality control?
A
set up of machines maintenance and cleaning of machines interpretation of results checks to ensure values are acceptable (control test) recording
23
Q
what does the level of cleaning of biochemistry machines depend on?
A
level of use - if used frequently then may not need to be cleaned every time
24
Q
what should be checked during the maintenance of biochemistry machines?
A
temperature and pH of reagents and that they are up to date. This ensures reactions happen properly and enzymes have optimum working conditions
25
why is quality control of biochemistry results so important?
decisions may be made based on wrong values - even euthanasia
results may have been wrong for a prolonged period of time without anyone being aware
26
what are the 2 main variables which affect test results?
biological
| analytical
27
what are the 2 key biological factors which can affect test results?
inter-individual
| intra-individual
28
what are the 3 analytical factors which can affect test results?
pre-analytical (before)
analytical (during)
post-analytical (after)
29
what variables will affect the result most pre-test?
biological and pre-analytical
30
what are inter-individual variables?
inherent differences between groups of animals due to the effects of species, breed, age and sex
31
what is an example of a common inter-individual variable associated with species?
cats have lower PCV than dogs
32
what are common inter-individual variables associated with age?
growing dogs have higher Ca, phosphate, and ALP but lower total protein concentration than adult dogs (this will also differ between breeds)
33
what are intra-individual variables?
transient differences in the same animal due to environment/external factors
34
what are examples of environmental/external factors that will form intra-individual variables?
diet, excitement, reproductive status, drugs, method of sampling
35
what factors should be minimised?
intra-individual
36
how can intra-individual diet factors be minimised?
all patients fasted for 8-12 hours pre biochemistry
37
what are the main pre-analytical factors that affect biochemistry results?
```
poor sampling/type of sampling
haemolysed, lipaemic or icteric plasma
wrong anticoagulant
wrong anti-coagulant/blood ratio
wrong tube
transport of sample
storage
contamination with EDTA
```
38
in what order must anticoagulant/blood ratios be respected?
clotting
haematology
biochemistry
39
how should samples be stored/transported?
refrigerated not frozen unless serum/plasma are separated
40
how can contamination with EDTA be avoided?
don't touch tube when transferring sample from the clotting test tube as it will ruin biochemistry tests
41
what method may give a falsely low reading during enzyme testing?
kinetic (enzymatic) assays instead of end point assays
42
what is the difference between end point and kinetic (enzymatic) assays?
kinetic (enzymatic) assays measure activity rather than amount of enzyme at the pre-determined end point
43
why may kinetic (enzymatic) assays give a false low?
if there is high amount of enzyme which leads to substrate depletion and so reduced enzyme activity
44
how can false lows in kinetic (enzymatic) assays be retested?
diluting solution
45
what are reference intervals?
most prevalent value in the population
46
what percentage of the population fall inside reference intervals?
95% of population
| 1 in 20 will have readings outside RI and be healthy
47
as as well between patients where will reference intervals vary?
between biochemistry machines
48
describe the pattern of changes in liver enzymes due to acute hepatic injury
ALT is most sensitive and shows initial increase, will also be the last to decrease
AST is less sensitive as it is found within the mitochondria of hepatocytes
49
describe the pattern of changes in liver enzymes due to cholestasis
cholestatic enzymes will increase to deal with increase bile presence (blockage preventing drainage)
if issue is prolonged then bile will begin to cause damage leading to increase in damage enzymes
50
what is an increase in bilirubin known as?
hyperbilirubinaemia
51
what does hyperbilirubinaemia lead to?
jaundice
52
what is bilirubin?
breakdown product of heamoglobin in RBC
53
where is bilirubin processed and excreted?
processed in liver and excreted in the faeces through bile
54
what are the 3 causes of hyperbilirubinaemia?
pre-hepatic: increased RBC breakdown
hepatic: decreased bilirubin processing (e.g. liver disease)
post-hepatic: decreased bilirubin excretion (e.g. bile duct obstruction)
55
where are bile acids produced and excreted?
in the liver and excreted into small intestine via bile duct
56
where are bile acids reabsorbed?
in distal small intestine
57
what is reabsorption of bile acids known as?
enterohepatic recycling
58
what are the 3 main reasons for bile acid elevation?
decreased hepatic function
decreased bile flow (cholestasis)
portosystemic shunt
59
what is a portosystemic shunt?
flow of blood through portal vein to liver enters the systemic circulation instead
60
what does a jaundiced sample suggest about bile acids?
they will be high
61
describe the bile acid stimulation test
fast overnight, take fasted sample into a plain tube, feed, take a sample into a plain tube 2 hours after feeding
62
what must be checked before sample collection?
tube type, volume of blood/plasma required for each test
63
why does the volume of blood not equal the volume of plasma?
PCV makes up around 45% of blood volume in dogs which is not usable for biochemistry
64
how much blood should you aim to collect when sampling?
3x the amount of plasma volume required - allows for PCV and less complaint patient
65
how can haemolysis and platelet clumping be avoided in sampling?
clean stick
| avoid vacuum and collapse of veins by not drawing back on syringe too quickly
66
what tubes can be used for biochemistry tests?
plain tube/serum
heparin tube
Oxf tube
67
what should Oxf tubes be used for?
measurement of glucose when exact values needed as Oxf stops RBC continuing to use glucose
68
what is happening to glucose in plain and heparin tubes?
cells are still living and so glucose is still being consumed
69
what does lipaemia lead to visibly?
turbid/milky serum/plasma
70
what is lipaemia due to?
presence of lipids
71
what effect will lipaemia have on values?
will increase and decrease some values in plasma/serum due to extra lipid fractions and turbidity caused by lipids
72
what will ideal biochemistry systems do with regards to lipaemia?
warn of presence and grade it
73
does lipaemia affect hematology?
yes
74
what does lipaemia affect that influences results?
light transmission which will affect spectrophotometric assays)
can result in apparent dilution of normal substances in aqueous component leading to a false low (e.g. electrolytes)
75
what are the physiological reasons for lipaemia?
post-prandial (need fasted samples!!)
76
what are the pathological reasons for lipaemia?
endocrinopathies e.g. diabetes, hypothyroidism, hyperadrenocortisolism
77
will pathological lipaemia dissappear when fasted?
no
78
what does haemolysis cause?
red coloured serum/plasma due to free haemoglobin/myoglobin
79
what may cause haemolysis?
in vitro - pathological
| in vivo - improper handling/sampling *most common*
80
what does haemolysis increase in biochemistry?
plasma/serum values of some compounds/enzymes due to increased concentration of RBC
81
what does haemolysis decrease in biochemistry?
plasma/serum values of compounds due to decreased concentration of RBC
82
what does haemolysis interfere with?
determinations of colour interference (spectrophotometric assays) or chemical interactions
haematology
83
what is icterus?
yellow serum/plasma
84
what effect does jaundice have on biochemistry?
depends on the biochemistry being done
85
what is icterus/jaundice due to?
increased bilirubin - pathological
86
does jaundice interfere with haematology?
no
87
does icteric plasma/serum interfere with assays?
yes - should be rerun with a hopefully better sample
88
what are the main 5 types of in-house biochemistry analysers?
glucometres
'dry' biochemistry analysers (reagents are dry)
'wet' biochemistry analysers (reagents are wet)
electrolyte analyser
blood gas analyser
89
describe the basic principle of spectrophotometry
light source is passed through the sample and based on how much light of a particular wavelength is absorbed we can calculate concentration of the compound of interest
90
what law is spectrophotometry based on?
beers law
| absorbance = constant + light pathway distance through cavette - concentration of substance of interest
91
what factors can interfere with spectrophotometry?
haemolysis and lipaemia can affect how much light is absorbed and can affect accuracy of results
92
how can haemolysis and lipaemia be prevented?
fasting and careful collection/handling
93
describe the best way to prevent haemolysis at all steps
careful sampling technique
avoid delays to sample processing
separate plasma/serum from sample as early as possible
refrigerate separated sample
94
what parameters are used to measure the function of the pancreas?
PLI and TLI
95
what does PLI stand for?
pancreatic lipase immunoreactivity
96
what does TLI stand for?
tripsenogen like immunoreactivity
97
what does elevated PLI indicate?
pancreatic injury
98
what does TLI indicate?
pancreatic functional mass - how much exocrine function remains (EPI)
99
what is EPI?
exocrine pancreatic insufficiency
100
why are the bile duct and pancreas so often linked in illness?
bile and pancreatic juice drain through a common duct. If there is cholestasis this can lead to secondary pancreatitis and vice versa
101
what 3 parameters are measured to show kidney function?
urea
creatinine
SDMA
102
what does increased urea in a biochemistry screen indicate?
dehydration, renal disease, urinary obstruction/rupture, heart disease
103
what does decreased urea in a biochemistry screen indicate?
liver failure as urea is made in the liver
104
what does increased creatinine in a biochemistry screen indicate?
as with urea: dehydration, renal disease, urinary obstruction/rupture, heart disease in medium and large dogs
105
what does decreased creatinine in a biochemistry screen indicate?
muscle wastage (very small dogs and cats)
106
is SDMA affected by muscle mass?
no, unlike creatinine
107
what must urea, creatinine and SDMA be assessed in conjunction with?
urine analysis
108
what do urea, creatinine and SDMA show?
glomerular filtration rate
109
how are urea, creatinine and SDMA linked?
tend to increase and decrease together
110
define azotemia
increased serum urea and/or creatinine concentration
111
where is azotemia detected?
in the blood
112
what are the 3 types of azotemia?
pre-renal
renal
post-renal
113
what can cause pre-renal azotemia?
decreased renal perfusion (hypovolaemia, dehydration)
114
what can cause renal azotemia?
disease - only seen when 60-70% of nephrons are damaged
115
what causes post-renal azotemia?
urinary tract obstruction or rupture
116
define uremia
specific clinical syndrome (vomiting, anorexia and ulcreation)
117
when does uremia develop?
when high levels of toxic substances (e.g. urea, creatinine)are present in the blood (azotemia) which causes reduced renal excretion
118
what is CK enzyme linked with?
muscle damage
119
what would increased CK indicate?
skeletal muscle damage or haemolysis
120
what other parameters may be increased alongside CK?
ALT and AST as they are also found within muscle
121
what is the totel proteins measurement formed of?
albumin + globulin
122
where is albumin produced?
liver
123
how can total proteins be measured?
refractometry
| biochemistry analyser
124
what are the issues with refractometry when calculating total proteins?
may also measure glucose, cholesterol, urea etc, and is affected by lipaemia
125
what information about total protein will be given by biochemistry analyser?
albumin value and total protein
126
how can globulin be calculated from biochemistry analyser results?
total protein - albumin = globulin
127
what is the role in the blood of proteins?
maintaining oncotic pressure as well as individual protein functions
128
how may age affect total proteins?
increased in neonates after colostrum ingestion, decreases as maternal antibodies drop
129
what is the most common protein in the blood?
albumin
130
what can cause increased albumin in the blood?
dehydration
131
what can cause reduced albumin in the blood?
```
mild inflammation
liver disease
kidney disease
GI disease
haemorrhage
```
132
what is SPE?
serum protein electrophoresis
133
what is SPE used for?
evaluating the different groups of protein in serum
134
what do protein fractions migrate according to, during SPE?
size and charge
135
what can cause high glucose?
diabetes
stress
steroid therapy
136
what can cause low glucose?
```
wrong blood tube/time delay
insulinoma
insulin overdose
some tumors (very metabolically active)
```
137
what does fructosamine indicate?
glucose level for past 2-3 weeks
138
what is fructosamine used to diagnose?
diabetes
139
what are the common liver parameters measured during biochemistry analysis?
ALT, GLDH, ALP, GGT, bilirubin, bile acids
140
what are the common kidney parameters measured during biochemistry analysis?
urea, creatinine, SDMA and urine analysis
141
what are the common pancreas parameters measured during biochemistry analysis?
PLI, TLI
142
what are the common muscle parameters measured during biochemistry analysis?
CK, AST
143
what are the common protein parameters measured during biochemistry analysis?
TP, albumin, APPs (acute phase proteins)
144
what are the common electrolyte parameters measured during biochemistry analysis?
Na, K, Cl, Ca, PO4
145
what are the common glucose parameters measured during biochemistry analysis?
fructosamine
146
what are the common lipid parameters measured during biochemistry analysis?
triglycerides and cholesterol
147
what are the common hormone parameters measured during biochemistry analysis?
T4, cortisol, TSH, ACTH, insulin
148
what are the common haematology parameters measured during biochemistry analysis?
RBC, WBC, Plt, blood smear
149
what are the common haemostasis parameters measured during biochemistry analysis?
PT, aPTT, TCT, BMBT
150
what can cause increased total proteins?
false high with lipaemia
dehydration
inflammation
neoplasia
151
what can cause decreased total proteins?
```
haemorrhage
GI disease
very young animals
renal disease
hepatic disease
```
152
which conditions have the largest effect on albumin?
renal disease
| hepatic disease
153
what is haemostasis?
the ability to stop bleeding
154
what does defective haemostasis lead to?
leads to haemorrhage, generally known as coagulopathies
155
what does excessive haemostasis lead to?
leads to thrombotic events
156
what anticoagulant is used for clotting tests?
EDTA
157
what are the most important considerations when performing clotting tests?
respect amount of blood required
perform clean venapuncture
separate plasma ASAP
freeze if sending away
158
what are the 3 stages of haemostasis?
primary
secondary
tertiary
159
when does primary haemostasis occur?
first stage, occurs when the needle punctures the vein and lasts seconds to minutes
160
what is primary haemostasis associated with?
platelet numbers, function and vascular function leading to the formation of the platelet plug
161
what does primary haemostasis require?
enough platelets
platelets to function properly
von Wilburn factor
162
what happens during secondary haemostasis?
stabilisation of clot in minutes to hours
163
what is secondary haemostasis associated with?
formation of fibrin mesh which stabilises platelet plug
164
what happens during tertiary haemostasis?
return to normal vascular flow
165
what is tertiary haemostasis associated with?
breakdown of the clot
166
what can be used to measure tertiary haemostasis?
D-Diamers
167
what are the requirements for normal primary haemostasis?
vessel wall
platelets in correct number and functionin gproperly
vWF
168
what are the tests available for primary haemostasis?
BMBT
platelet count
platelet function testing
histopathology
169
what are the common disorders of primary haemostasis?
IMTP - immune mediated thrombocytopenia
vW disease
angiostrongylus
170
what are the requirements for normal secondary haemostasis?
coagulation factors
calcium
vitamin K
fibrin
171
what are the tests available for secondary haemostasis?
Activated Clotting Time
Prothrombin Time
Activated Partial Thromboplastin Time
Thrombin Clotting Time
172
what are the common disorders of secondary haemostasis?
congenital factor deficiencies
warfarin toxicity
severe liver disease
angiostrongylus
173
what are the requirements for normal tertiary haemostasis?
tissue plasminogen activator (tPA)
| plasmin
174
what are the tests available for tertiary haemostasis?
FDPs
| D-Diamers
175
what are the common disorders of tertiary haemostasis?
DIC
176
What is BMBT?
buccal mucosal bleeding time
177
how is BMBT tested?
under sedation - standardised cut made on patients gum. Blood collected with filter paper, taking care not to disturb the clot, and is absorbed until it stops
178
what are the normal BMBT for cats and dogs?
normal dog <3.3 mins
GA dog <4 mins
GA cat <3.3 mins
179
what causes prolonged BMBT?
moderate to severe thrombocytopenia
thrombopathia - inherited or acquired
vWM disease
180
what screening can BMBT be used for?
pre op of breeds at risk of vWD e.g. doberman
181
how quickly will hemorrhage start after trauma in a patient with primary haemostasis disorders?
immediately
182
what type of bleeding is typically seen in a patient with primary haemostasis disorders?
capillary bleeding: skin, mucosa, epistaxis, GI and urinary tract.
petechail haemorrhage
ecchymosis (bruising)
183
how quickly will hemorrhage start after trauma in a patient with secondary haemostasis disorders?
usually a small delay
184
what type of bleeding is typically seen in a patient with secondary haemostasis disorders?
internal bleeding: joints, muscles, body cavity (pleural, mediasteinum)
haematomas
haemoartroses
185
what bleeding is typically seen in a patient with both primary and secondary haemostasis disorders?
```
GI bleeding
meleana
haematoemesis
haematochezia
epistaxis
haematauria
```
186
what is thrombocytopenia?
low platelets
187
how is activated clotting time tested?
whole blood is collected and allowed to clot in commercially available tubes
188
what are the normal activated clotting time values for dogs?
<90 sec
189
what are the normal activated clotting time values for cats?
<60 sec
190
when is activated clotting time prolonged?
if there is a marked deficiency in one/several clotting factors
affected by platelet number and function
191
what does the clotting cascade result in?
fibrin (clot)
192
what are the 2 branches of the clotting cascade
extrinsic
| intrinsic
193
what can be used to measure extrinsic pathway of the clotting cascade?
prothrombolin time (PT)
194
what can be used to measure intrinsic pathway of the clotting cascade?
activated partial thromboplastin time (APTT)
195
what are PT and APTT tests checking for?
presence of clotting factors and function
196
what causes prolonged PT and APTT tests?
Increase in clotting times due to reduction in clotting factor (if individual factor is reduced to <20-30% of normal concentration)
197
where are most clotting factor and cofactors made?
in the liver
198
where do most clotting factors and cofactors circulate?
in the blood
199
what can be used to test for fibrinolysis?
FDPs
| D Diamers
200
why to FDPs elevate?
increase on clot formation and lysis as well as inflammation
201
why do D Diamers elevate?
increases with clot formation and lysis
202
what are D Diamers?
degradation products of cross linked fibrin (stable clot)
203
when may elevated D Diamers be seen?
post surgery/trauma
DIC secondary to inflammation
neoplasia
thromboembolytic disease
