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Table 2 2 × 2 contingency table for statistical calculation of SEN, SP, PPV and NPV for the detection of a positive A. pleuropneumoniae lung colonization status by bacteriological culture examination of tonsilar samples (n = 163)

From: Evaluation of the predictive value of tonsil examination by bacteriological culture for detecting positive lung colonization status of nursery pigs exposed to Actinobacillus pleuropneumoniae by experimental aerosol infection

  Samples positive by lung tissue examination Samples negative by lung tissue examination
Samples positive by tonsil examination 122 (true positive) 7 (false positive)
Samples negative by tonsil examination 22 (false negative) 12 (true negative)
Sensitivity (SEN) true positive / (true positive + false negative) = 84.72%
Specificity (SP) true negative / (true negative + false positive) = 63.16%
Positive predictive value (PPV) true positive /(true positive + false positive)= 94.57%
Negative predictive value (NPV) True negative / (true negative + false negative) = 35.29%