Table 3.

Risk Prediction of D-Dimer, CD4 Cells and Their Combination in Older Adults with COVID-19

	Cut-off	AUC	95% CI	P
D-dimer①	0.65 mg/L	0.703	0.585–0.820	0.004
CD4②	268 cell/µL	0.804	0.695–0.912	<0.001
CD4/D-dimer	431	0.794	0.690–0.897	<0.001
Tandem combination	① and ②	0.812	0.692–0.932	<0.001
Parallel combination	① or ②	0.694	0.583–0.805	0.006

Notes: ① the level of D-dimer; ② CD4 cells count, the CD4-positive T-lymphocytes count; CD4/D-dimer, ratio of the CD4 cells count to the D-dimer level; Tandem combination, the level of D-dimer > 0.65mg/L and the CD4 cells count < 268 cell/µL; Parallel combination, the level of D-dimer > 0.65mg/L, or the CD4 cells count < 268 cell/µL.