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Table 1 2 × 2 Table for diagnostic test studies

From: Evidence-based gynaecological practice: clinical review 3. The use of imaging for pre-operative planning in deep infiltrating endometriosis involving the rectum

  Target disorder
Present Absent
Diagnostic test result Positive True positive a False positive b
Negative False negative c True negative d
  1. Sensitivity a/(a + c)
  2. Specificity d/(b + d)
  3. Positive predictive value a/(a + b)
  4. Negative predictive value d/(c + d)
  5. Prevalence (pre-test probability) (a + c)/(a + b + c + d)
  6. Positive likelihood ratio (LR+) sensitivity/(1-specificity)
  7. Negative likelihood ratio (LR−) (1–sensitivity)/specificity