Table 3. Univariate and multivariate Cox proportional hazards regression analysis of progression of illness with CALL and RAS Score parameters.

HRs were calculated comparing without comorbidity versus with comorbidity, age ≤60 years versus >60 years, lymphocyte count >1.0 x 10/L versus ≤1.0 x 10/L, LDH ≤250 U/L versus LDH 250-500 U/L or >500 U/L, respiratory rate ≤20 b/m versus 21-25 b/m or 26-30 b/m or >30 b/m, resting oxygen saturation ≥95% versus 90%-94% or <90%, normal A-a gradient versus elevated A-a gradient, 10 feet O₂ desaturation <3% versus ≥3%.

HR, hazard ratio; CALL, comorbidity, age, lymphocyte and LDH; RAS, respiratory assessment scoring; LDH, lactate dehydrogenase; b/m, breaths per minute; A-a gradient, alveolar arterial oxygen gradient; O₂, oxygen. 

	Univariate Cox analysis HR (95% CI)         p-Value		Multivariate Cox analysis HR (95% CI)        p-Value
Comorbidity
Without	1	_	1	_
With	0.97 (0.66-1.43)	0.876	0.89 (0.59-1.33)	0.564
Age (Years)
≤60	1	_	1	_
>60	1.87 (1.30-2.68)	<0.001	1.50 (1.02-2.22)	0.041
Lymphocyte (x109/L)
>1.0	1	_	1	_
≤1.0	2.30 (1.61-3.29)	<0.001	1.76 (1.20-2.57)	0.003
LDH (U/L)
≤250	1	_	1	_
250-500	2.43 (1.26-4.68)	0.008	2.17 (1.13-4.20)	0.020
>500	4.09 (2.15-7.75)	<0.001	3.33 (1.74-6.37)	<0.001
Respiratory rate (b/m)
≤20	1	_	1	_
21-25	2.21 (1.24-3.95)	0.007	1.40 (0.76-2.57)	0.281
26-30	4.85 (2.65-8.90)	<0.001	2.40 (1.24-4.64)	0.009
>30	6.66 (4.28-10.38)	<0.001	3.03 (1.77-5.19)	<0.001
Resting oxygen saturation (%)
≥95	1	_	1	_
90-94	2.57 (1.37-4.82)	0.003	1.52 (0.76-3.06)	0.239
<90	7.83 (4.41-13.89)	<0.001	2.41 (1.15-5.06)	0.020
A-a Gradient
Normal	1	_	1	_
Elevated	5.71 (3.21-10.17)	<0.001	2.14 (1.04-4.39)	0.038
10 feet O2 desaturation test (%)
<3	1	_	1	_
≥3	3.89 (2.33-6.49)	<0.001	1.44 (0.78-2.62)	0.227