case unit 6 - diagnostics Flashcards
what does specificity test
how many people are healthy
what does sensitivity test
how many people actually have the disease
if the sensitivity is 84%
then 84% of people with the disease will be correctly tested as +ve
if the specificity is 53%
then 53% of healthy people will be correctly tested -ve
importance of a good diagnosis
correct and appropriate therapy can be prescribed
better prognosis
early detection
reasons why a diagnosis would be made
if a sick person visits the doctor
if an ‘at risk’ population gets screened
- clinical referral and subsequent tests may follow this
what types of measurements may be taken in a diagnosis
symptoms e.g. spots, fever physiology e.g. temp, bp blood-borne e.g. blood hormone/glucose levels biopsy-based e.g. cancer antigens other e.g. questionnaire, voc
what are VOCs
volative organic compounds
metabolic by-product of the disease present in swear, breath, urine, poo
disadvantage of measuring VOCs
each measurement could represent a combination of substances
why are VOCs a good diagnostic measure
non-invasive
quick
cheap
what is the diagnostic cut-off
vertical line between those that test +ve and -ve on rgpah
anyone above the cut off line has the disease
anyone below is healthy
overlap in the distributions gives false results
types of imaging used in diagnosis
x-rays
histology
karyotyping
disadvantages of imaging as a diagnostic tool
expensive
subjective
requires expert consultation
invasive - often used as an end diagnosis
use of automated diagnosis
e.g. detection of melanomas
AI used to recognise malignant moles from photo analysis
consultant standard
t-SNE visualtion used to detect different carcinomas
use of DNA as a biomarker if they think you have the disease
use PCR
sequence candidate genes for monogenic diseases
use of DNA as a biomarker if they are unsure whether you have the disease or not
test your cell free (cfDNA) for SNPs
use of cfDNA in cancer
DNA is released into your blood e..g ctDNA (circulating tumour) purify cfDNA amplify the target genes (those that are commonly mutated in cancers e.g. p53, Ras) sequence target regions
advantages of using cfDNA
non-invasive
like a liquid biopsy
disadvantages of using ctDNA
often low presence of ctDNA in blood
different ctDNA characteristics among patients
what are micro-vesicles
membrane fragments released into the blood
what is the new trisomy screen
NIPS - Non-invasive pre-natal screen
mothers blood sample also contains foetal DNA
cf-DNA tested
next gen sequencing used
advantages of the new trisomy screen (NIPS)
more sensitive and more specific test
diagnosis of mental capabiltiy
hard
classification of behavioural tests (think trump test)
DSM-5
what is DSM-5
diagnostic and statistical manual of mental disorders
