Table 4.

Association of patient laboratory and x-ray findings, and Pneumonia Severity Index with ICU admission within three days of presentation

Characteristics	Derivation cohort			Validation cohort
	Admission to ICU ≤ 3 days		P value	Admission to ICU ≤ 3 days		P value*
	No (4392)	Yes (201)		No (1865)	Yes (102)
Laboratory and x-ray findings, %
Arterial pH < 7.35	2.3	10.9	< 0.001	2.6	19.6	< 0.001
BUN ≥ 10 mmol/L	13.0	37.8	< 0.001	12.9	30.4	< 0.001
Sodium < 130 mEq/L	3.9	11.7	< 0.001	3.0	13.0	< 0.001
Glucose ≥ 14 mmol/dL	4.8	9.9	0.001	5.1	10.9	0.02
Haematocrit < 30%	4.5	10.9	< 0.001	4.7	11.8	0.002
WBC < 3 or ≥ 20 G/L	9.1	18.9	< 0.001	8.4	18.6	< 0.001
PaO2 < 60 mmHg	21.9	54.7	< 0.001	18.9	56.9	< 0.001
Pleural effusion	10.4	21.9	< 0.001	10.1	17.6	0.01
Multilobar infiltrates	22.0	41.8	< 0.001	22.2	39.2	< 0.001
Pneumonia Severity Index, %
Class I	28.4	5.0	< 0.001	28.6	4.9	< 0.001
Class II	24.0	10.9		24.9	13.7
Class III	19.1	17.9		18.7	22.5
Class IV	23.0	46.8		22.2	35.3
Class V	5.4	19.4		5.5	23.5

Admission to ICU ≤ 3 days refers to patients who were admitted to an ICU within three days of presentation to the emergency department. * P value refers to the variables associated with admission to ICU within 3 days of presentation. BUN = blood urea nitrogen; ICU = intensive care unit; PaO₂ = arterial partial pressure of oxygen; WBC = white blood cell.