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Table 2 Sensitivity, specificity, PPV and NPV according to different C-reactive protein (CRP) and procalcitonin (PCT) cut offs in the patients with excluded or definite community acquired pneumonia

From: Diagnostic accuracy of C-reactive protein and procalcitonin in suspected community-acquired pneumonia adults visiting emergency department and having a systematic thoracic CT scan

Biomarkers' cut-off Total Excluded CAP Definite CAP p value Se Sp PPV NPV LR+ AUC
(N = 169) (N = 71) (N = 98)
n (%) n (%) n (%)
CRP cut-off
  > 20 mg/L 133 (79) 41 (58) 92 (94) <0.001 93.9 42.2 69.2 83.3 1.62  
  > 30 mg/L 123 (73) 35 (49) 88 (90) <0.001 89.8 50.7 71.5 78.2 1.82  
  > 50 mg/L 109 (64) 26 (37) 83 (85) <0.001 84.7 63.4 76.1 75.0 2 .31 0.787
  > 70 mg/L 92 (54) 24 (34) 68 (69) <0.001 69.4 66.2 73.9 61.0 2.05  
  > 100 mg/L 73 (43) 15 (21) 58 (59) <0.001 59.2 78.9 79.4 58.3 2.80  
PCT cut-off
  > 0.10 μg/L 115 (68) 39 (55) 76 (78) 0.003 77.5 45.1 66.1 59.2 1.41  
  > 0.25 μg/L 74 (44) 25 (35) 49 (50) 0.061 50.0 64.7 66.2 48.4 1.41 0.655
  > 0.50 μg/L 53 (31) 16 (23) 37 (38) 0.044 37.7 77.5 69.8 47.4 1.67  
CRP >49.5 mg/L and PCT cut-off combined
 PCT > 0.13 μg/L 83 (49) 21 (29) 62 (63) <0.001 63.2 70.4 74.6 58.1 2.13  
 PCT > 0.1 μg/L 90 (53) 22 (31) 68 (69) <0.001 69.4 69.0 75.5 62.0 2.23  
 PCT > 0.25 μg/L 68 (40) 21 (29) 47 (48) 0.018 47.9 70.4 69.1 49.5 1.62  
 PCT > 0.5 μg/L 51 (30) 15 (21) 36 (36) 0.041 36.7 78.9 70.6 47.4 1.74  
  1. Abbreviations: CAP community acquired pneumonia, Se sensitivity, Sp specificity, PPV positive predictive value, NPV negative predictive value, LR likelihood ratio, AUC area under the curve