Table 4.

Evaluation of D-Dimer, CD4 Cells, and Their Combination in the Risk Prediction of Severe or Critical Illness in Older Adults with COVID-19

	Sen (95% CI)	Spe (95% CI)	PPV (95% CI)	NPV (95% CI)
D-dimer①	0.810(0.626–0.993)	0.596(0.492–0.699)	0.321(0.191–0.451)	0.930(0.861–0.992)
CD4②	0.810(0.626–0.993)	0.798(0.713–0.883)	0.486(0.312–0.660)	0.947(0.895–0.999)
CD4/D-dimer	0.857(0.694–1.020)	0.730(0.636–0.824)	0.429(0.272–0.585)	0.956(0.906–1.006)
Tandem combination	0.714(0.504–0.925)	0.910(0.850–0.971)	0.652(0.442–0.863)	0.931(0.877–0.985)
Parallel combination	0.905(0.768–1.042)	0.483(0.377–0.589)	0.292(0.179–0.406)	0.956(0.893–1.018)

Notes: ^①The level of D-dimer>0.65mg/L; ^②The CD4 cells count, the CD4-positive T-lymphocytes count < 268 cell/µL; CD4/D-dimer, the ratio of the CD4 cells count to the D-dimer level < 431; 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.

Abbreviations: Sen, sensitivity; Spe, specificity; PPV, positive predictive value; NPV, negative predictive value.