Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemical Pathology > LFTs > Flashcards

LFTs Flashcards

1
Q

Calculate globulin gap

A

Total protein - albumin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Albumin method in your lab?

A

Bromocresol green (dye binding method) at pH 4.2, measured at 596/694 nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Critically discuss dye binding methods for albumin

A

Two methods used in most labs: BCG and BCP, based on greater affinity of albumin for these dyes compared to other proteins. BCP slightly more specific, and results are slightly lower than BCG results (BCG reacts with globulins as well), particularly in patients with kidney failure. This has implications for reference intervals for albumin AND for parameters derived from albumin eg corrected calcium, globulin gap, calculated free testosterone. Dye-binding assays also tend to be less accurate when serum/plasma protein composition is abnormal. The many ligands of albumin do not typically affect dye-binding assays of serum/plasma.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Causes of decreased albumin

A
  1. Decreased synthesis
    - malnutrition
    - malabsorption
    - chronic liver failure
  2. Increased catabolism
    - sepsis
    - Malignancy
    - other catabolic states
  3. Increased plasma volume
    - excess water intake
  4. Redistribution
    - ascites
    - oedema
    - sepsis
  5. Increased loss
    - protein losing enteropathy
    - nephrotic syndrome
    - burns causing plasma loss
  6. Physiologic
    - pregnancy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is P-5’-P? What role does it play in the measurement of aminotransferases?

A

Vitamin B6, P-5’-P or pyridoxal-5’-phosphate acts as an amino group acceptor, and in its amino form - pyridoxamine-5’-phosphate - acts as an amino group donor.

P-5’-P is a coenzyme for aspartate and alanine aminotransferase. It acts as the amino group acceptor from alpha-ketoglutarate/pyruvate and amino group donor to form glutamate in the reactions catalysed by AST and ALT respectively.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why is ALT preferred over AST as a marker of parenchymal liver injury?

A

ALT is more specific than AST and increased activity of ALT persists longer than AST. Thus the incremental benefit of routine determination of AST in addition to ALT may be limited

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Bilirubin is conjugated by what enzyme? What is the gene encoding this enzyme?

A

Uridine diphosphate glucuronyltransferase 1A1
UGT1A1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is delta-bilirubin and how is it formed?

A

Bilirubin monoglucuronide can be transported from the hepatocyte into the blood via ABCC3 transporters. In the blood, bilirubin monoglucuronide binds to albumin and forms delta-bilirubin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is bilirubin transported in blood, prior to conjugation?

A

Bound to albumin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

4 fractions of bilirubin

A
  1. Unconjugated
  2. Monoconjucated
  3. Diconjugated
  4. Delta-bilirubin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a bilirubinometer?

A

Point of care screening device for measuring bilirubin in neonates to determine if blood draw required. Transcutaneous spectrophotometric detection at 437nm (max absorbance of bilirubin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Pre-analytical factors in bilirubin collection

A

Sensitive to light (causes photolysis, decreasing concentration)
Haemolysis
Some drugs (method dependent)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is albumin bound bilirubin taken up by hepatocytes?

A

By OATP transporters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

methods for bilirubin determination

A
  1. Diazo (reference)
  2. Enzymatic
  3. HPLC
  4. Spectrophotometric (transcutaneous bilirubinometer)
  5. Dry chemistry
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Reference method for bilirubin

A

Diazo method

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the Diazo method for bilirubin

A

Reaction of diazotised sulfanilic acid (diazo reagent) to produce 2 coloured azodipyrroles that are measured spectrophotometrically, either at 530nm or after addition of alkaline tartrate, at 530 nm. Accelerated by alcohol/variety of other accelerators eg sodium benzoate. Accelerator causes dissociation of unconjugated bilirubin from albumin, so that both unconjugated and conjugated bilirubin can be measured. To prevent unconjugated bilirubin from reacting in direct methods, pH maintained ~1.0.

17
Q

Bilirubin method in your lab

A

Enzymatic. Bilirubin is converted to biliverdin by bilirubin oxidase. The decrease in absorbance at 435/460nm is measured by spectrophotometry. Detection of total bilirubin occurs at pH 8. To detect direct bilirubin, p is 3.7-4.5. At this pH range, the enzyme oxidizes bilirubin conjugates and delta-bili but not unconjugated bili. At pH 10, bilirubin oxidase selectively oidizes the 2 glucuronides.

18
Q

Liver disease causes an increase in which fraction of bilirubin?

A

Conjugated

19
Q

Significance of urine bilirubin

A

Only appears in disease and reflects an increase in plasma conjugated bilirubin

20
Q

In which organs is ALP present?

A

Liver, kidney, bone, intestine, placenta

21
Q

Describe the multiple forms of ALP. A diagram may be helpful

A

True isoenzymes
Chromosome 1 - tissue nonspecific - bone, liver, kidney. Encoded by same gene but differ in CHO content (sialic acid chains)
Chromosome 2 - germ cell, placental, intestinal and fetal intestinal.

22
Q

Activators of the ALP enzyme?

A

Mg2+, Co2+, Mn2+

23
Q

T or F: Zn2+ is an activator of ALP

A

False. Zn2+ is a constituent metal ion

24
Q

Inhibitors of ALP activity?

A

Phosphate, borate, oxalate, cyanide

25
Q

T or F: ALP increase is greater in extrahepatic than intrahepatic obstruction

A

True. ALP increase can exceed greater than 4xURL in extrahepatic obstruction (eg stone, head of pancreas ca). Increase is proportional to the degree of obstruction.

26
Q

Apart from obstruction, what other pathologies can cause extreme increases in ALP? (up to 10-12x URL?)

A

Cancer - advanced HCC or widespread liver mets

27
Q

Name one prognostic use of ALP

A

In patients with primary biliary cirrhosis, ALP >2xURL predicts liver Tx/death

28
Q

Describe the expected change in ALP with pregnancy

A

A rise of up to 2-3xURL by third trimester due to placental ALP

29
Q

Describe the malignancy forms of ALP

A

Regan isoenzyme - essentially identical to placental ALP, heat stable to 65C
Kasahara isoenzyme - modified form of nonplacental isoenzymes
Nagao isoenzyme - germ cell ALP

30
Q

Does ALP activity increase or decrease with refrigeration?

A

Increase

31
Q

You want to measure ALP on a frozen sample, what preparation is needed?

A

Allow to thaw for 18-34 hours to allow full enzyme reactivation

32
Q

50% of isolated increases in liver enzymes are caused by which 5 aetiologies?

A
  1. Drugs
  2. Alcohol
  3. NAFLD
  4. HBV
  5. HCV
33
Q

What wavelength is albumin measured at?

A

BCG 628nm
BCP 600nm

34
Q

Most common cause of isolated increase in unconjugated bilirubin?

A

Gilbert’s syndrome

35
Q

Causes of hepatitic picture

A
  1. Viral
  2. Alcoholic
  3. NAFLD
  4. Toxic
  5. Ischaemic
  6. Drug induced
  7. Autoimmune
  8. Rare - Wilson’s, AAT deficiency, haemochromatosis
36
Q

Causes of chronic hepatitis

A

HBV
HCV
AIH type 1
AIH type 2
Wilson’s
Drug
AAT deficiency
NAFLD
Idiopathic

37
Q

Tests for AIH type 1

A

ANA, anti-SMA

38
Q

Tests for AIH type 2

A

SLA, anti-LKM1

Chemical Pathology (27 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions