Laboratory indicators in asymptomatic and presymptomatic COVID-19 patients
On admission, the most common computed tomography (CT) findings were ground-glass opacity and lung-texture increase in asymptomatic (83% and 50%, respectively), presymptomatic (83% and 61%, respectively), and symptomatic (92% and 62%, respectively) patients, with no significant intergroup differences (18). Other chest CT characteristics such as fuzzy boundary (range 8–17%), consolidation (0–12%), and pleural thickening (range 4–7%) were observed in asymptomatic, presymptomatic, and symptomatic patients, but without statistical significance. Interestingly, pleural effusion (7%), fine reticular opacity (2%), and lymph node enlargement (1%) were only observed in symptomatic patients (Fig. 3A). The presence of enlarged lymph nodes in symptomatic patients may indicate a stronger immune response.
To obtain more information on the affected organs, we compared laboratory indicators between the groups of asymptomatic, presymptomatic, and symptomatic COVID-19 patients. The rates of abnormal (one-fold away from the reference range) laboratory indicators associated with liver and kidney function were all above 60% in each group (Fig. 3B), and the rates of abnormal laboratory indicators associated with heart function were less than 40%. Specifically, when the threshold for abnormality was set to two-fold points from the reference range, asymptomatic patients showed lower rates of abnormal laboratory indicators of hepatic function (2.8% vs 20%,P -value < 0.05) and cardiac function (5.7% vs10%, P -value > 0.05) and comparable rates in terms of kidney function (11.43% vs 10%, P -value > 0.05, Fig. 3C) than presymptomatic patients. Abnormal levels of lactate dehydrogenase, albumin, uric acid, D-dimer (DD), C-reactive protein, and calcium were less frequently observed in asymptomatic and presymptomatic patients than in symptomatic patients (Fig. 3D, Table S2 and Table S3). These analyses indicate that the liver and kidney were the most common affected organs in all COVID-19 patients, whereas indicators for heart and liver function showed the most significant differences between asymptomatic and presymptomatic patients.