I am doing the series of molecular typing methods in the differentiation of clinical isolates especially, Mycobacterium tuberculosis. So, to differentiate each technique from others I am getting confused with sensitivity and specificity.
Hi Kathirvel Maruthai
Specificity - how specific you are in your target ex. choosing an specific antibody for quantifying your particular protein
Sensitivity - how for your signal (treated group) to noise (control and non treated) is concern in your experiment. ex - background signal in your Blank control while you are performing your ELISA
These factors arise due to cross re-activity or may be by cross contamination.
All the best
Hi, in simple words, specificity refers to the capacity of the method to discriminate or differentiate molecular compounds or cellular compounds that have similar characteristics. For other hand sensivity refers to the capacity of your method to detect this compounds. Under a certain limit ( e.g: a method for detect iron with a sensitivity of 1 mM) you can´t detect iron o you can´t ensure the accurate of the results)
I hope that this help you to understand this concepts.
Regards.
Hi Kathirvel
Plz read attached article which is very recent... I hope it will definitely help you....
Gud Luck
Wikipedia can help:
http://en.wikipedia.org/wiki/Receiver_operating_characteristic
An example:
If you test for the presence of a specific strain of bacteria in 100 samples and 20 of your samples carry that strain (and 80 don´t):
A method with 95% sensitivity (equals true positive rate, TPR)) will detect the presence of that strain in 19/20 = 95% of strain-carrying samples.
Specificity means true negative rate (TNR) - e.g. if your method is able to correcly classify 72 of your 80 negative samples as negative has a specificity of 72/80 = 90%.
Usually sensitivity and specificity are dependend on the threshold you set for distinguishing between positives and negatives (e.g. number of cycles in a real-time PCR, or band intensity in an agarose gel) Varying that threshold from minimum to maximum possible and plotting all obtained values for TPR vs FPR will generate a ROC curve and the area below that curve will give you an optimal measure of the quality of your method.
For my naiive brain. Sensitive test is the one that can pick up almost everyone but most of the pick-ups may not be a true one. Specific test is the one that use a very stringent criteria to prove the case is a real one but the test is so stringent that we may miss some true cases. Theoretically the two are contradict to each other. Since you are interested in TB then PPD is a relatively sensitive test (or PCR is the most sensitive test) but to see the true TB bacilli is the most specific test. I hope this may help.
Let’s start with what is the meaning of sensitivity and specificity:
Sensitivity means that: how much the test can detect the positive cases.
Specificity means that: how much the test can detect the negative cases.
Ideally sensitivity and specificity are 100%, but it is not on the earth; so when to accept what?
Consider specificity if you have a fatal disease with no treatment
Consider sensitivity if you are screening to prevent transmission of a preventable disease
NB: Also notes the other terms: Positive and negative predictive value , Likelihood ratio and accuracy
NB: this site is really useful: www.bibalex.org/supercourse/
Sensitivity and Specificity are analogues of Accuracy and Precision...in
Bio-statistics. ie.
When you do molecular typing for clinical isolates of Myco.tuberculosis...they signify as how specific (precise) your method / titre to Myco.tuber alone and if so as how sensitive (accurate) your titre is for the same at very low and very high dilutions.
(pl.ref. the following for more know how on bio-statistics....
Accuracy and precision - Wikipedia, the free encyclopedia
en.wikipedia.org/wiki/Accuracy_and_precision....The analogy used here to explain the difference between accuracy and precision is ... Accuracy may be determined from Sensitivity and Specificity, provided ... of one same conceived entity, measured or calculated by different methods, in the )
if you calculate your experimental data as mean+_ SDM or mean +_ SEM values and if your 'p' values are less than 0.001 (ie.less than 1 in thousand) your experimental results are significant.
Try this. We have just launched an interactive online website to help anyone wanting to work out & interpret diagnostic tests for accuracy and clinical utility.
The website is www.clinicalutility.co.uk. On that page go to the excel xls doc for best value
You can you this sheet...We have just launched an interactive online website to help anyone wanting to work out & interpret diagnostic tests for accuracy and clinical utility.
The website is www.clinicalutility.co.uk. On that page go to the excel xls doc for best value
Hi,
Calculating Sensitivity & Specificity, PPV & NPV Tutorial, This may be helpful.
https://youtu.be/BVH8XU75XZQ
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