When only COVID-19+ patients were evaluated, the levels of circulating CHI3L1 were increased in patients with hypertension versus those without hypertension; patients who were admitted versus those who were sent home from the ED; patients who were older than 50 years old versus younger individuals; and patients with comorbid diseases versus COVID-19+ patients without concurrent comorbid disorders (Figure 6, G–J). Here, CHI3L1 is linked to COVID-19.