| Thoracic imaging tests for the diagnosis of COVID‐19 |
| Question |
What is the diagnostic accuracy of chest imaging (computed tomography (CT), chest X‐ray and ultrasound) in the evaluation of people suspected of having COVID‐19? |
| Population |
Children or adults suspected of having COVID‐19 |
| Index test |
Chest imaging tests used for the diagnosis of COVID‐19, including:
chest CT chest X‐rays ultrasound of the lungs
|
| Target condition |
COVID‐19, the illness following acute infection with SARS‐CoV‐2 |
| Reference standard |
A positive diagnosis for COVID‐19 by one or a combination of the following.
A positive RT‐PCR test for SARS‐CoV‐2 infection, from any manufacturer in any country, from any source, including nasopharyngeal swabs or aspirates, oropharyngeal swabs, bronchoalveolar lavage fluid (BALF), sputum, saliva, serum, urine, rectal or faecal samples Positive on WHO criteria for COVID‐19, which includes some testing RT‐PCR‐negative Positive on China CDC criteria for COVID‐19, which includes some testing RT‐PCR negative Positive serology in addition to consistent symptomatology Positive on study‐specific list of criteria for COVID‐19, which includes some testing RT‐PCR‐negative Other criteria (symptoms, imaging findings, other tests, infected contacts)
A negative diagnosis for COVID‐19 by one or a combination of the following.
People with suspected COVID‐19 with negative RT‐PCR test results, whether tested once or more than once. Currently healthy or with another disease (no RT‐PCR test)
|
| Limitations in the evidence |
| Risk of bias |
Participant selection: high in 10 (20%) studies and unclear in 22 (43%) studies Application of index tests – chest CT: high in 5/41 (12%) studies and unclear in 15/41 (37%) studies Application of index tests – chest X‐ray: unclear in 6/9 (67%) studies Application of index tests – ultrasound of the lungs: unclear in 4/5 (80%) studies Reference standard: high in 20 (39%) studies and unclear in 20 (39%) studies Flow and timing: high in 2 (3.9%) studies and unclear in 22 (43%) studies |
| Concerns about applicability of the evidence |
Participants: high in 1 (2%) study Index test – chest CT: low in all 41 studies Index test – chest X‐ray: high in 1/9 (11%) study and unclear in 1/9 (11%) study Index test – ultrasound of the lungs: unclear in 1/5 (20%) study Reference standard: low in all 51 studies |
| Findings |
We included 51 studies (19,775 participants suspected of having COVID‐19, 10,155 (51%) cases) Studies evaluated chest CT scans (41 studies), chest X‐ray (9 studies) and ultrasound of the lungs (5 studies) Chest CT was sensitive and moderately specific in the diagnosis of COVID‐19 in suspected cases. Chest X‐ray was moderately sensitive and moderately specific in the diagnosis of COVID‐19 in suspected cases. Ultrasound of the lungs was sensitive, but not specific in the diagnosis of COVID‐19 in suspected cases. Sensitivity analysis in chest CT studies showed that publication status had a minimal effect on our findings. The ‘threshold’ effect in chest CT studies that used the CO‐RADS scoring system demonstrated a trade‐off between sensitivity and specificity; as the threshold for index test positivity increased from 2 to 5, sensitivity decreased, and specificity increased. There was no statistical evidence indicating that reference standard conduct and definition of index test positivity were sources of heterogeneity for chest CT studies. Indirect test comparisons showed that chest CT has a higher specificity than ultrasound. Chest CT and ultrasound have similar sensitivities, chest CT and chest X‐ray have similar sensitivities and specificities, and chest X‐ray and ultrasound have similar sensitivities and specificities. |
| Evidence for participants suspected of having COVID‐19 |
| Imaging modality |
Sensitivity (95% CI) |
Specificity (95% CI) |
Number of participants (cases) |
| Chest CT |
87.9% (84.6 to 90.6) |
80.0% (74.9 to 84.3) |
16,133 (8110) |
| Chest X‐ray |
80.6% (69.1 to 88.6) |
71.5% (59.8 to 80.8) |
3694 (2111) |
| Ultrasound of the lungs |
86.4% (72.7 to 93.9) |
54.6% (35.3 to 72.6) |
446 (211) |
| Predicted outcomes |
| Given various prevalence settings, predicted outcomes for the number of individuals receiving a false positive result or a false negative (missed) result per 1000 people undergoing chest CT, chest X‐ray, and ultrasound of the lungs are outlined as follows. |
| Predicted outcomes per 1000 people undergoing chest CT |
| Prevalence of COVID‐19 |
Positive CT result
n (95% CI)
|
False positive CT result
n (95% CI)
|
Negative CT result
n (95% CI)
|
False negative CT result
n (95% CI)
|
| 50% |
440 (423 to 453) |
100 (79 to 126) |
400 (374 to 421) |
60 (47 to 77) |
| 20% |
176 (169 to 181) |
160 (126 to 200) |
640 (599 to 674) |
24 (19 to 31) |
| 5% |
44 (42 to 45) |
190 (149 to 238) |
760 (712 to 801) |
6 (5 to 8) |
| Predicted outcomes per 1000 people undergoing chest X‐ray |
| Prevalence of COVID‐19 |
Positive CT result
n (95% CI)
|
False positive CT result
n (95% CI)
|
Negative CT result
n (95% CI)
|
False negative CT result
n (95% CI)
|
| 50% |
403 (346 to 443) |
143 (96 to 201) |
357 (299 to 404) |
97 (57 to 154) |
| 20% |
161 (138 to 177) |
228 (154 to 322) |
572 (478 to 646) |
39 (23 to 62) |
| 5% |
40 (35 to 44) |
271 (182 to 382) |
679 (568 to 768) |
10 (6 to 15) |
| Predicted outcomes per 1000 people undergoing ultrasound of the lungs |
| Prevalence of COVID‐19 |
Positive CT result
n (95% CI)
|
False positive CT result
n (95% CI)
|
Negative CT result
n (95% CI)
|
False negative CT result
n (95% CI)
|
| 50% |
432 (364 to 470) |
227 (137 to 234) |
273 (176 to 363) |
68 (30 to 136) |
| 20% |
173 (145 to 188) |
363 (219 to 518) |
437 (282 to 581) |
27 (12 to 55) |
| 5% |
43 (36 to 47) |
431 (260 to 615) |
519 (335 to 690) |
7 (3 to 14) |
|
CI: confidence interval; CT: computed tomography; n: number; RT‐PCR: reverse transcription polymerase chain reaction |
