case unit 1 - cholera Flashcards
which averages should you use for quantitative data
median
mean
why is the mode not useful for quantitative data
there might be more than one mode
each value in the study might only appear once
mode could be a high or low number (far from middle)
what methods do you use to quantify variation?
sd
iqr
range
benefits of case report study design
can identify new trends/diseases
helps detect new drug side effects
identifies rare manifestations of a disease
case report study
reports a new case of newly identified symptoms or outcomes
observation of symptoms, diagnosis and treatment of the individual case
presents hypothesis to be confirmed by another study type
types of observational study
case report
case control
cohort
limitations of case report study
may not be able to generalise the individual cases
report not based on systematic studies
other possible explanations for outcomes
report only focuses on rare event, may be misleading
case control study
‘retrospective’ - disease has already occurred
compares patients with disease to those without
evaluates relationships between risk factors and disease
estimates odds
benefits of case control study
good for studying rare diseases
takes little time as disease has already occurred
multiple risk factors can be studied at the same time
risk factor-disease associations can be established
limitations of case control
problems with data quality and data relies on memory
recall bias as people remember worse things
hard to find suitable control group
cohort study
evaluations of causative risk factors determined after following cohort populations during their disease
measurements taken of outcomes
benefits of cohort study
subjects are matched which limits influence of confounding variables
standardisation of criteria/outcomes
easier and cheaper than rct
limitations of cohort study
difficult to identify cohorts due to confounding variables
no randomisation
blinding of subjects is difficult
takes time for outcome of interest to occur
randomised control study
subjects randomly assigned to control or intervention group
only variable studied is the expected difference between the groups
benefits of rct
no population bias due to randomisation
easier to mask/blind subjects
statistical analysis using known methods easy
clearly identified populations
limitations of rct
expensive
time-consuming
volunteering populations not representative of entire population
causation of disease not revealed
practice guidelines
produced by panel of experts
guidelines on prevention/treatment/diagnosis/prognosis of disease
informs health care professionals
systematic review
combines and summarises all information from previous studies on one health topic or question
meta-analysis
statistical method of combining results from different studies to increase statistical power
what are kochs postulates used for?
establishing a causative relationship between microbe and disease
what do koch’s postulates require
that the pathogen is present in all cases of the disease
that the pathogen can be isolated from the host and grown in pure culture
the pathogen grown in culture can cause the same disease when inoculated into a healthy, susceptible lab animal
that pathogen can then be re-isolated and be the same as the originally isolated pathogen
aetiology
study of the manner of causation of the disease
kuhn
paradigm shift
what is meant by the term paradigm shift
a fundamental change in the basic concepts and experimental practices of a scientific disciplicne
when does a paradigm shift occur
when there are enough significant anomalies that cannot be explained by the current paradigm
why can pcr be used to detect viral dna in human tissue samples
viral dna sequences will be different to any human dna sequences
outline process of pcr for viral dna
identify specifc viral dna sequence
make forward and reverse primers
mix sample and primers and heat to 96 to denature
cool to 60 to allow complementary base pairing - annealing
heat to 72 - optimum for dna polymerase- extension
how do you separate dna after pcr
using agarose gel
separated on a size basis
uses of qPCR
quantifies amount of a specific sequence of dna
quantifies expression levels of mRNA
why do we need reverse transcriptase for qPCR
pcr only works on dna not rna
what does reverse transcriptase do
converts mRNA to cDNA
how is cDNA produced by PCR measured
by a dye that fluoresces when bound to DNA
delta Ct
the change in expression in control sample
uses of next generation sequencing
determining the DNA sequence of large numbers of different DNA molecules
genome sequencing
cDNA sequencing
illumina next gen seq method
fragment the genome of dna
each fragment gets own area of machine
dna amplified into clusters
add coloured labelled nucleotides in rounds
use of computer in next gen seq
rebuilds dna fragments
looks for overlapping sequences to assemble the gene
deep sequencing
multiple sequencing to reduce error
exome sequencing
only sequence part of the genome
what is a variable
a set of characteristics (data values)
e.g. gender/systolic blood pressure
types of variable
categorical
quantitative
types of categorical variable
nominal - labelled, unordered
ordinal - ranked
what type of variable is ‘disease severity’
ordinal
relative frequency
way of describing categorical data
proportion or percentage
bar chart
graphical description of categorical data
ways to describe quantitative data
average
variation
symmetry
relative quantification (RQ)
how many fold increase in expression
ussing delta ct on pcr cycle graph
