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Table 2 Methods to calculate sensitivity, specificity, PPV, NPV and accuracy

From: Screening for aneurysms of the abdominal aorta using a simple screening device

  Abdominal ultrasound  
Positive Negative
Aorta Scan
 Positive TP FP PPV = TP/(TP + FP)
 Negative FN TN NPV = TN/(FN + TN)
  Sensitivity = TP/(TP + FN) Specificity = TN/(FP + TN) Accuracy = (TP + TN)/All
  1. FN false negative, FP false positive, NPV negative predictive value, PPV positive predictive value, TN true negative, TP true positive