Case unit 6 Flashcards
test parameters from imaging
shape, size, number, specific molecule
Scoring systems often used
Subjectivity can be an issue
Expert opinion often required
when designing a test what do we need
something that marks the disease and is different in healthy and ill indivduals
what are volatile organic compounds
present in sweat, urine, poo and breath
metabolic products
quick, cheap and non-invasive
what is cell free DNA
circulating tumour (ct)DNA
DNA released into the blood
tumour and normal cells
non-invasive test
liquid biopsy
PCR - Sequence certain DNA to detect genes
allows you to detect certain tumours by genes
use of GWAS as a screening method
GWAs correlates the presence of genetic variants with the risk of developing a disease
Identification of an individual SNP profile may indicate risk of developing a condition
Sensitivity
the proportion of people with the disease who will have a positive result. In other words, a highly sensitive test is one that correctly identifies patients with a disease.
Also called the true positive rate
Specificty
the proportion of people without the disease who will have a negative result. In other words, the specificity of a test refers to how well a test identifies patients who do not have a disease.
also called the true negative rate
Positive predicitve value
probability that a positive result in a hypothesis test means that there is a real effect. It is the probability of patients who have a positive test result actually having the disease.
PPV calculation
PPV = number of true positives / number of true positives + number of false positives
or
PPV = Sensitivity x Prevalence / Sensitivity x prevalence + (1- specificity) x (1-prevalence)
Specificty calculation
True negative/ true negative + false postive
sensitivity calculation
true positive/ flase negative + true positive
