interpreting info Flashcards
what is accuracy?
how close to true value it is
what is precision?
how reproducable analytical result it is
what are internal IQC samples?
samples that are taken multiple times a day - producing replicate result
what are external QC samples?
samples every 6 months ish and test instructions come from main lab and you have to measure using specific method and don’t know expected result until main lab coordinates all and publishes findings
what is reference interval on lab experiment graph?
it’s the central section of findings - normally 95%
explain using reference to graph why people can sometimes be misdiagnosed?
becuase there is some overlap in values - that’s why you have diagnostic cut-off and ranges of values that are “normal”
what does sensitivity mean? (in context of false positives/negative)
% of people who have true positives over false negatives (i.e % of people who are told they have cancer & have it over the % percentage of people who are told they don’t have cancer and do have it)
- you want as high as possible
what does specificity mean? (in context of false negatives/false positives)
& people who don’t have disease that have negative test
what is
a) positive predictive value
b) negative predictive value
a) % of people positive test
b)% people with negative result that don’t have disease
what do the positive and negative predictive values used for?
they’re used if for example you get positive result - you use positive predictive value for that test to see likelihood of true positive result
how do you calculate prevalence?
people who have disease / total people sampled
when would you use prevalance?
has big impact on how useful test is
= if prevalance either really or high or really low then diagnostic test pointless e.g. go do pregnancy test on all the patients in antenatal clinic - pointless as obviously they’re all pregnant
