Wednesday, January 2, 2008

some statistical hints; by Osama M. Warda, MD

  • Seneitivity= the ability of the test to diagnose the disease in its presence: i.e. = true positive / all positive by the refernce test (TP+FN)
  • Specificity= the ability of the test to exclude the disease in its absence. i.e = true negative/ all negative by the reference test(TN+FP)
  • Positive predictive value= [TP/ all positive by the screening test(TP+FP) ]x 100
  • negative ,, ,, = [TN/all negative by ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,( TN+FN)]X100
  • DIAGNOSTIC ACCURACY = [(TP+TN)/all studied (TP+FP+TN+FN)]X 100

true positive (TP)= positive by screeninig test and by reference test

True negative (TN)= negative by screeninig test and by reference testfalsepositive (FP)= positive by screening test BUT negative by reference test

false negative (FN)= negativeby screening test BUT positive by reference test

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