Table 3.

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

	Chest X-ray	CT chest	Mean difference	P value
Total (n)	860	302
True positives (n)	305	162	–	–
False positives (n)	125	55	–	–
True negatives (n)	187	56	–	–
False negatives (n)	243	29	–	–
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.