Table 3

Diagnostic accuracy metrics for CXR and CT chest with RT-PCR for SARS-CoV-2, as the reference standard

Chest X-rayCT chestMean differenceP value
Total (n)860302
True positives (n)305162
False positives (n)12555
True negatives (n)18756
False negatives (n)24329
Apparent prevalence (95% CI)0.50 (0.47 to 0.53)0.72 (0.66 to 0.77)0.22 (0.04 to 0.21)<0.0001**
True prevalence (95% CI)0.64 (0.60 to 0.67)0.63 (0.58 to 0.69)−0.00 (−0.09 to 0.03)0.111
Sensitivity (95% CI)0.56 (0.51 to 0.60)0.85 (0.79 to 0.90)0.29 (0.19 to 0.38)<0.0001**
Specificity (95% CI)0.60 (0.54–0.65)0.50 (0.41 to 0.60)−0.10 (−0.25 to 0.04)0.119
Positive predictive value (95% CI)0.71 (0.66 to 0.75)0.75 (0.68 to 0.80)0.04 (−0.06 to 0.14)0.492
Negative predictive value (95% CI)0.43 (0.39 to 0.48)0.66 (0.55 to 0.76)0.22 (0.06 to 0.37)0.005*
Positive likelihood ratio (95% CI)1.39 (1.19 to 1.62)1.71 (1.41 to 2.08)0.32 (−0.22 to 0.89)0.258
Negative likelihood ratio (95% CI)0.74 (0.64 to 0.84)0.30 (0.21 to 0.44)0.44 (−0.64 to −0.21)0.022*
Diagnostic accuracy (95% CI)0.57 (0.54 to 0.61)0.72 (0.66 to 0.77)0.15 (0.06 to 0.23)<0.0001**
  • *Significant difference at the <0.05 level; **significant difference at the <0.0001 level.

  • CXR, chest X-ray; RT-PCR, reverse transcriptase PCR.