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Table 5 Probability increases (%) for P(1+) and for P(0-) in relation to prevalence and LRs

From: Questioning the “SPIN and SNOUT” rule in clinical testing

  PPV probability increase (%) for P(1+)
prevalence prevalence
SE SP LR+ 0.2 0.4 0.6 0.8 0.2 0.4 0.6 0.8
0.8 0.8 4.00 0.50 0.73 0.86 0.94 0.30 0.33 0.26 0.14
0.4 0.8 2.00 0.33 0.57 0.75 0.89 0.13 0.17 0.15 0.09
0.8 0.4 1.33 0.25 0.47 0.67 0.84 0.05 0.07 0.07 0.04
0.4 0.4 0.67 0.14 0.31 0.50 0.73 −0.36 −0.42 −0.36 −0.21
    NPV     probability increase (%) for P(0-)    
    prevalence = P [1]     1-prevalence = P(0)    
SE SP LR- 0.2 0.4 0.6 0.8 0.8 0.6 0.4 0.2
0.8 0.8 0.25 0.94 0.86 0.73 0.50 0.14 0.26 0.33 0.30
0.4 0.8 0.75 0.84 0.67 0.47 0.25 0.04 0.07 0.07 0.05
0.8 0.4 0.50 0.89 0.75 0.57 0.33 0.09 0.15 0.17 0.13
0.4 0.4 1.50 0.73 0.50 0.31 0.14 −0.07 −0.10 −0.09 −0.06
  1. Diagnostic test calculators are available on the internet to determine SE, SP, LRs and or to determine post-test probabilities given prevalence and test characteristics [12, 13].