Sensitivity, Specificity, Accuracy of Bio-tests-الاحصاء الحياتي-محاضرة الحساسية والتخصصية للتحاليل

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Diagnostic measures (Sensitivity, Specificity, and Accuracy)
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The performance of screening tests can be measured by calculating functions known (in this context) as
-sensitivity: a measure of the ability of the test to detect people who have the disease) and
-specificity: a measure of its ability to identify people who do not have it).
Such calculations require reliable identification of true and false positives and negatives, which in turn requires a ‘gold standard’ or definitive diagnostic test that unequivocally identifies the presence or absence of the disease.

The numbers of true and false positive and negative results can also be used to calculate the predictive value (PV) of a positive or negative result, i.e.
PV+: the probability that a positive test will correctly classify the person being tested.
PV-: the probability that a negative will correctly classify the person being tested.
Accuracy = (TN + TP)/(TN+TP+FN+FP) = (Number of correct assessments)/Number of all assessments).
[Accuracy is the proportion of true results, either true positive or true negative, in a population. It measures the degree of veracity of a diagnostic test on a condition].
The concepts of sensitivity, specificity and predictive values can also be used to describe the performance of tests done for diagnostic purposes.