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Molecular Cell Biology FoM > Diagnostics > Flashcards

Diagnostics Flashcards

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1
Q

Why do we do tests?

A
  • Confirming the diagnosis
  • Shot in the dark- allows the diagnosis to be narrowed down
  • Assessing stages of severity
  • Medico-legal reasons (paternity test)
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2
Q

What are the downsides of tests?

A
  • Costs
  • Inaccuracies
  • Invasiveness of some tests and anxiety
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3
Q

Describe a diagnostic pathway

A
  • Demographics
  • Symptoms
  • Physical examination
    Simple bedside tests
  • Diagnostic test- surrogate biomarker which substitutes for clinical endpoint
  • Real disease
  • Many diagnoses are made through screening rather than patient presentation
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4
Q

Describe the ideal test

A
  • Identifies every case of disease (100% sensitive)
  • Does not predict anyone from the healthy group as sick (100% specific)
  • Non-invasive
  • Cheap
  • Instant
  • Easy to interpret data- presence of marker being actual marker
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5
Q

Describe how to develop a test- looking for a biomarker

A
  • Comparing an equal number of healthy/diseased individuals
  • If threshold too low, many people could be falsely classified
  • Gold standard vs new test
  • Validation with gold standard- e.g. confirmation through biopsy
  • How often does the test match the biopsy
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6
Q

What is sensitivity?

A

Proportion of true positives that are correctly identified

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7
Q

What is specificity?

A

Proportion of true negatives that are correctly identified

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8
Q

What is a type 1 error?

A
  • False positive
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9
Q

What is a type 2 error?

A
  • False negative
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10
Q

What is the equation for sensitivity?

A

True positive/ (true pos + false neg)

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11
Q

What is the equation for specificity?

A

True negative/ (true neg + false pos)

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12
Q

What is the positive predictive value?

A

Proportion of patients with a positive test who are correctly diagnosed

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13
Q

What is the negative predictive value?

A

Proportion of patients with a negative who are correctly diagnosed

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14
Q

What is the equation for PPV?

A

True pos/ (true pos + false pos)

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15
Q

What is the equation for NPV?

A

True neg/ (true neg + false neg)

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16
Q

Which description should be used to determine the usefulness of the diagnostic test in a clinical setting and why?

A
  • PPV

- Information gathered from population studies rather than case control studies

17
Q

How is the choice of test determined?

A
  • By the physical properties of the biomarker
18
Q

What are the genetic categories of diagnostic tests?

A
  • Cytogenetic

- Sequence dependent

19
Q

What are the types of tests in cytogenetic diagnostics?

A
  • Fluorescence In Situ Hybridisation (FISH)
  • Chromosome Microarray Analysis
  • Amniocentesis/ Chorionic villous sampling
  • These help identify chromosome abnormalities
20
Q

Describe fluorescence in situ hybridisation

A
  • Sequenves specific to each chromosome pair labelled with specific dye colour
  • Chromosomes and DNA heat treated and cooled together
  • Complementary strands hybridised and become fluorescent
  • Chromosomes imaged using fluorescent microscope
  • Able to identify single genes on chromosomes
21
Q

What are the types of tests in sequence dependent diagnostics?

A
  • Polymerase Chain Reaction
  • Clinical uses of PCR
  • Whole genome sequencing
22
Q

Describe the polymerase chain reaction

A
  • Amplifies specific desired regions of genome in an exponential manner
  • Requires DNA, primers, oligonucleotides and DNA polymerase
  • Primers complementary base pair to specific area of gene sequence
  • Sequential heating and annealing followed by DNA replication- polymerase
  • Increases amount of material to be sequenced
23
Q

What are clinical uses of PCR?

A
  • Pathogen detection- viruses, bacteria and fungi- if viruses, some are RNA
  • Oncology- mutations associated with transformation of cell can predict response to anti-tumour drugs (KRAS confers resistance to anti-EGS-R therapy)
  • Mutation analysis, e.g. cystic fibrosis transmembrane conductance regulator CTFR (pre-implantation)
  • HLA typing for organ/tissue donors
24
Q

Describe whole genome sequencing

A
  • Determines the entire DNA sequence in one go
  • Being introduced clinically
  • Personalised medicine- vital for guiding therapeutic intervention)
  • Splicing variation
  • Copy number variation
  • Single nucleotide variation
25
Q

What are other categories of diagnostics tests?

A
  • Immuno-detection

- Biochemical/biophysical tests

26
Q

What are the immuno-detection types of diagnostic tests?

A
  • ELISA

- Immuni-Histo-Chemistry (IHC)

27
Q

Describe the ELISA test

A
  • Enzyme-linked immune-sorbent assay
  • Detects antibodies made in response to an antigen
  • Autoantibodies in circulation
  • Biomarkers in body fluids (proteins/chemicals)
  • Dependent upon specific antibodies
28
Q

Describe the IHC test

A
  • Immuni-HistoChemistry

- Uses antibodies for determining antigen tissue distribution

29
Q

Describe biochemical tests

A

LDH assay measures tissue damage in serum samples using enzymic properties

30
Q

Describe biophysical assays

A

Like pulse oximeters measures blood oxygen sats

Molecular Cell Biology FoM (12 decks)

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