Sensitivity And Specificity

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Accuracy of data sets

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The interpretation of sensitivity, specificity, prevalence and accuracy in Nuclear Medicine :1 The interpretation of sensitivity, specificity, prevalence and accuracy in Nuclear Medicine Ericka Alexis NMT 1002 Group IV


Sensitivity :2 Sensitivity Or, true positive fraction (TPF) is the percentage or fraction of ill patients who have a positive test All patients are put into different categories True positive (TP)- persons with a positive test result who are truly ill. False positive (FP)- persons with a positive test result who are not ill. True negative (TN)- person with a negative test result who are truly well. False negative (FN)- person with a negative test result who are not well.


Specificity :3 Specificity Or, true negative fraction (TNF) is the percentage or fraction of well patients who have a negative test.


Positive & Negative Fractions :4 Positive & Negative Fractions True positive fraction (TPF) Used in sensitivity TPF= (TP) (TP+ FN) True negative fraction (TNF) Used in specificity TNF = (TN) (TN + FP)


Prevalence :5 Prevalence The fraction or percentage of ill person in the study populations.


Accuracy :6 Accuracy A parameter that specifies the total number of correct answers regardless of being or well. Means that the test is correctly diagnosed Accuracy = (total number of correct) (total number of persons)


Food for thought :7 Food for thought Why are these tests done? Why is it important for doctors to have this information? Why is this information different in different facilities? Who takes these tests? Can these tests be wrong?


Answers :8 Answers It classifies the test range in probabilities. To accurately advise the patient with the best possible diagnosis. Every hospital and/or facility has different ranges of what is significant and what is not. It could be anyone! Yes, this is why accuracy is very important for the doctor.


References :9 References Christian, P., Bernier, D., Langan, J., (2004). Nuclear Medicine and PET Technology and Techiniques, Fifth Edition, 30-34. British Medical Journal http://www.bmj.com/epidem/epid.html Rapid Diagnostics http://www.rapid-diagnostics.org/accuracy.htm