B10 H+S Flashcards
What is sensitivity?
true positives, the proportion of positives that are correctly identified. “will it pick up everyone that has the disease”
sensitivity equation
sensitivity= true positives/ true positives and false negatives (how many are true based on all the people with)
what is specificity?
true negatives, measures the proportion of negatives that are correctly identified. “will it pick up only the people with the disease, thus leaving all the people without the disease”
specificity equation
specificity= true negatives/ true negatives+ false positives (how many are false based on all the people that are false)
what does true positive mean?
test indicates disease when there is a disease
what does true negative mean?
test indicates no disease when no disease
false positive?
says is disease when no disease
positive predictive value?
probability of subjects with positive screening having the disease
negative predictive value?
probability that subjects with a negative screening truly don’t have the disease
Sensitivity test useful when?
when the result is negative- sensitivity rule out or snout. (if sensitivity is high and you are negative, youre likely to be negative)
specificity test useful when?
if the test is positive you can be quite sure that they have the disease- sensitivity rule in or spin.
+ve predictive value calculation?
true positive/ true positive+ false positive
how many people of the positives actually have the disease.
what is likelihood ratio?
likelihood that given test resultwould be expected in a patient with target disorder, compared to likelihood that same reusult would be in patient without target disorder (if +ve result, how likely to have disease?)
things commonly screened for?
Cancers PPD- TB prenatal tests ultrasound- AAA diabetic checks
limitations of screening?
cost and use of medical resources
adverse screening effects
stress and anxiety caused by false positive
pros of good screening
early detection, reduced risk of death
cons of good screening
some people get tests etc with no benefit, some may get ill despite it being negative.
what is sojourn time?
duration of a disease before clinical symptoms are apparent but is still detectable by screening.
what is length bias?
a form of selection bias, more likely to screen people with longer progressive diseases. Could show that screening lengthens life but its just cos longer sojourn time.
consequences of lead time bias?
disease with longer sojourn time easier to catch. Will get distorted picture of screening and prognosis
lead time bias?
the earlier you diagnose the disease through screening, longer the patient will appear to survive (same time regardless
consequence of lead time bias
survival inevitably longer following diagnosis due to extra time. Measure of effectiveness is deaths prevented, not survival.
pseudodisease meaning
subclinical disease that would not become overt before the patient dies of other causes
things BPH is elevated in?
prostate cancer, BPH, UTI
what is opportunity cost?
loss of alternatives when one is chosen.
what is distributive justice?
distributing finite reousources fairly.
Ways to distribute healthcare?
QALY, waiting list, compliance, lifestyle choices, ability to pay
3 ways confidentiality may be breached
statute (law
consent by patient
publics best interests
3 laws that oblige doctors to disclose info
public health act 1984
road traffic act 1988
prevention of terror 1989
