Molecular epidemiology Flashcards
what is molecular epidemiology
the contribution of genetic, epigenetic and environmental risk factors identified at the molecular level to the cause, distribution and prevention of disease
incorporates biomarkers
what is a biomarker
any substance, structure or process that can be measured in the human body or its products and may influence or predict the incidence or outcome of disease
what are the 3 types of biomarkers
exposure (environment)
effect (disease)
susceptibility (genetic contribution)
what are some examples of biomarkers
- blood glucose concentration - diabetes - either exposure or effect biomarker
- fMRI image of brain - measures blood flow so biomarker of exposure or effect
- CYP1A2 gene - suscptibility
what type of biomarker is blood pressure
it is a biomarker of effect because it is a biomarker for the RISK of stroke, heart attack or chronic renal failure
what type of biomarker is selenium concentration in toenails
selenium deficiency is implicated in cancer
it is a biomarker of exposure to dietary and supplementary selenium
why is there sometimes a problem with obtaining biomarkers
access to suitable tissue samples is not always possible particularly in healthy cohorts
‘surrogate’ tissues are used in their place
what are some considerations we have to make when using biomarkers
collection
transportation
storage
analytical reliability
technical considerations
ethics
what type of things to consider during sample collection
trained staff
special sample handling requirements
quality control
coded blind to exposure status
retrospective or prospective samples
what to consider during sample transportation
biobank or multicentre?
temperature control
appropriate labelling
transporting across national borders
safety declarations
tracking
what to consider within storing the sample
basic processing to reduce analysis - DNA extraction
stabilisation of analytes - prevent breakdown of substances
separation of components
monitoring freezer temperatures
what to consider during analytical reliability
validation
reproducibility
what are some technical considerations for biomarkers
poor quality control during collection, processing, storage can compromise biomarker measurements
intra-individual variation may exist unrelated to exposure
single measure at one point may not reflect typical status
disease may affect biomarker
what are ethical considerations for biomarkers
accessibility of tissues (e.g children)
appropriate/less invasive alternatives
feedback results to study participants?
implications of results e.g BRCA1 gene mutations are predictive of future risk in cancer
what to consider in study of ‘smoking increases risk of bladder cancer by causing DNA damage’ - and you want to measure the DNA damage
how much DNA can be obtained from urine sample?
short term or long term smoking exposure?
how much urine is needed? collected at specific time? how will it be collected?
