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 ruling in and out  

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what is important for 'ruling in' and 'ruling out'

sensitivity, specificity, PPV or NPV..

please do explain y



any ideas ppl..i got confused on this UW question and wasnt satisfied with their explanation..


sensitivity ie.. how many patients can the test detect are positive for disease vs how many people really have the disease. so sensitivity rules in the disease when the patient has it ( and sometimes rules it in falsely), but it rules OUT the disease when the patient does not have it. the more sensitve it is the fewer false negative here. if you are negative, you dont have the disease at all in a highly sensitive test. 100% sensitivity.

specificity ie how many of those without disease are correctly labelled as negative versus how many were labelled as not having the disease. this is a confirmatory test. it is not used for screening. so specificity rules out the disease if you dont have it. teh more specific it is the fewer the false positive, so if it says you are negative then you dont have the disease.

this is the way i understand ppv and npv. it may not be accurate. so beware.
ppv has to do with proportion of correctly positive people and total number of positive. so, the higher the ppv, the more 'specific' the test is cos there are fewer false positive.

npv has to do with 'the other one" the higher the value, the more sensitive it is cos it means that your false negatives are low. remember that a highly sensitive test has low or no false negative.

any good???raised eyebrow


well i a similar idea about the stuff, but a mega confusion was...errr... i can t recall!!


thanx. may god bless u smiling face

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