Table 2.

Association between ARDS onset time and survival time in the derivation dataset, the validation dataset, and the combined dataset

Dataset	Onset stage	N	%	28-day survival time				60-day survival time
				HR	95% CI		P	HR	95% CI		P
Derivation	Early	377	72.50	Ref				Ref
	Late	143	27.50	2.24	1.48	3.39	1.24 × 10−4	1.70	1.16	2.48	6.62 × 10−3
Validation	Early	226	63.48	Ref
	Late	130	36.52	2.16	1.33	3.51	1.95 × 10−3	1.78	1.15	2.75	9.80 × 10−3
Combined	Early	603	68.84	Ref
	Late	273	31.16	2.00	1.47	2.72	1.10 × 10−5	1.59	1.20	2.10	1.22 × 10−3

HR hazard ratio, 95% CI 95% confidence interval, HR 95% CI and P values were adjusted for variables collected within 24 h of ICU admission (APACHE III score, septic shock, pneumonia, multiple fractures, transfusion within 7 days prior to admission, vasopressors prior to admission, intubation, ventilation, and highest potassium level), variables collected at time of ARDS onset (PaO₂/FiO₂, platelet count, and creatinine level), and ICU 28-day ventilation-free days in the Cox proportional hazards model; ARDS onset within 48 h after admission was defined as early-onset, and otherwise as late-onset stage