Coronavirus Disease 2019 and Chest CT: Do Not Put the Sensitivity Value in the Isolation Room and Look Beyond the Numbers

With interest we read the systematic review and metaanalysis by Dr Kim and colleagues (1) published online in April in Radiology regarding the value of chest CT in diagnosing coronavirus disease 2019 (COVID-19) infection.Kim et al reported chest CT to have a high pooled sensitivity of 94% (95% confidence interval [CI]: 91%, 96%), but a low specificity of 37% (95% CI: 26%, 50%).However, we believe that there is no convincing evidence yet that chest CT achieves such a high sensitivity in diagnosing COVID-19 in clinical practice.Note that the majority of studies that were included in the meta-analysis by Kim et al (1) (58 of 63 studies) only enrolled patients with proven COVID-19 infection whereas patients without the disease were lacking.Strikingly, this is not in line with their exclusion criterion number 3: "lack of extractable data for a two-by-two contingency table."As a result, these 58 studies only allowed for the calculation of sensitivity, and not specificity.However, the diagnostic value of a test depends on its ability to discriminate between patients with and without disease (2).Sensitivity and specificity are intertwined entities and are both dependent on the threshold value that is applied to discriminate between patients with the disease and those without (2).Generally, creating a high sensitivity by applying a low threshold is at the expense of specificity (2).Multiple studies in the meta-analysis by Dr Kim and colleagues did not report which criteria were used as threshold value (1).The possibility that a low threshold was used remains a realistic scenario.Applying a low threshold in cohorts of patients suspected of having the disease (both with and without an actual COVID-19 infection) may result in virtually all patients classified as having the disease.As a result, sensitivity values in these individual studies and the pooled estimate that was calculated by Dr Kim and colleagues (1) may have been overestimated.It should also be noted that the five studies that did provide a 2 3 2 diagnostic contingency table had numerous methodologic flaws.The lack of high-quality evidence, rather than the mathematical numbers, should have been the main conclusion in the otherwise excellent work by Dr Kim and colleagues (1).