Clinical diagnosis of severe COVID-19: A derivation and validation of a prediction rule

Table 1 Patient demographics and clinical characteristics in the training and internal validation sets

	Training sets			Internal testing sets
	Mild, n = 224 (62.0%)	Severe, n = 38 (10.5%)	P value	Mild, n = 90 (25.8%)	Severe, n = 9 (2.5%)	P value
Age (yr)	48.5 (36.0-59.0)	64 (57.5-66.0)		43.0 (34.0-54.8)	64.0 (62.0-69.0)
≥ 60 yr	54 (24.1)	26 (68.4)	0.000	14 (15.6)	8 (88.9)	0.000
Sex			0.002			0.159
Male	106 (47.3)	29 (76.3)		38 (42.2)	6 (66.7)
Female	118 (52.7)	9 (23.7)		52 (57.8)	3 (33.3)
BMI > 24	57 (25.4)	11 (28.9)	0.000	22 (24.4)	4 (44.4)	0.024
BMI > 27	21 (9.4)	14 (36.8)		5 (5.6)	2 (22.2)
Onset to hospitalization (> 5 d)	62 (27.7)	25 (65.8)	0.000	34 (37.8)	5 (55.6)	0.000
Symptoms
Fever > 37.3°C	172 (76.8)	29 (76.3)	0.000	78 (86.7)	7 (77.8)	0.005
Fever > 39°C	8 (3.6)	7 (18.4)		1 (1.1)	2 (22.2)
Charlson index > 0	72 (32.2)	33 (86.8)	0.000	39 (43.3)	8 (88.9)	0.000
P/F	13 (5.8)	16 (42.1)	0.000	3 (3.3)	3 (33.3)	0.006
NLR > 2	80 (35.7)	15 (39.5)	0.000	39 (16.7)	3 (33.3)	0.009
NLR > 4	24 (10.7)	17 (44.7)		7 (7.8)	4 (44.4)
Score ≥ 7	31 (13.8)	35 (92.1)	0.000	13 (13.1)	9 (100)	0.000

BMI: Body mass index; P/F: PaO₂/FiO₂; NLR: Neutrophil/lymphocyte ratio.