Ancillary Diagnostic Tests
The optimal use of diagnostic imaging, biomarkers, and other nonmicrobiologic tests is rapidly evolving.

Radiographic Tests
Many centers have evaluated the utility of chest imaging for diagnosis. On chest radiography, bilateral pneumonia is the most frequently reported feature (range, 11.8% to 100%) and is more common than a unilateral focus (49, 50). Computed tomography is regarded as more sensitive than radiography, with several cohort studies reporting that most patients (77.8% to 100%) had ground glass opacities. Other features commonly reported with COVID-19 on chest computed tomography include a peripheral distribution, fine reticular opacities, and vascular thickening (51). Compared with serial nasopharyngeal sampling, chest computed tomography may be more sensitive than an RT-PCR test at a single time point for the diagnosis of COVID-19 (52, 53). In addition, artificial intelligence may help distinguish COVID-19 from other etiologic agents of community-acquired pneumonia (54). However, these findings are not completely specific to COVID-19 and do not exclude a co-infection or an alternative diagnosis (55).

Biomarkers Associated With COVID-19 Patients
The most common laboratory features reported in patients with COVID-19 include decreased albumin (75.8% [95% CI, 30.5% to 100%]), elevated C-reactive protein (58.3% [CI, 21.8% to 94.7%]), and elevated lactate dehydrogenase levels (57.0% [CI, 38.0% to 76.0%]), and lymphopenia (43.1% [CI, 18.9% to 67.3%]) (56). Other biomarkers that have been reported include increased erythrocyte sedimentation rates; elevated aspartate aminotransferase, alanine aminotransferase, and creatinine kinase levels; leukopenia; leukocytosis; and increased bilirubin and creatinine levels (57–59). Such findings are not surprising, because these biomarkers represent an inflammatory host response to SARS–CoV-2 or are early markers of end-organ dysfunction, similar to that seen in patients with sepsis (60). No biomarker or combination of biomarkers currently exists that is sensitive or specific enough to establish a diagnosis of COVID-19, or to pragmatically predict its clinical course.