FABP4 and COVID-19: Notably, we found out despite that FABP4 showed no significant change in COVID-19 patients, its level was negatively correlated with HDL-C in patients with HDL ≤ 1.0 mmol/l (R2 = −0.403, P = 0.087) and positively correlated with triglyceride in patients with TG ≥ 1.7 mmol/l (R2 = 0.821, P = 0.089), suggesting that it may influence lipid metabolism (Supplementary Fig. 4j).