Table 3.1‘2 × 2’ table for calculation of diagnostic test accuracy parameters

Reference standard positiveReference standard negativeTotal
Index test result positivea (true positive)b (false positive)a+b
Index test result negativec (false negative)d (true negative)c+d
Totala+cb+da+b+c+d = N (total number of test results in study)

Sensitivity = a/(a+c), specificity = d/(b+d), LR+ = sensitivity/(1–specificity), LR = (1–sensitivity)/specificity

From: 3, Guideline development methodology

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Antibiotics for Early-Onset Neonatal Infection: Antibiotics for the Prevention and Treatment of Early-Onset Neonatal Infection.
NICE Clinical Guidelines, No. 149.
National Collaborating Centre for Women's and Children's Health (UK).
London: RCOG Press; 2012 Aug.
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