Table 1

Basic characteristics of patient population: total population discharged in 2002 versus sample in present study

	Total population	Present study	Test of difference
	Total population	Present study	Statistic	p value
Number of admissions	2932	149
Mean (SD) age at admission (years)	48.0 (22.6)	52.7 (21.5)	t = 2.48	0.013
% male	55.1	57.7	χ² = 0.39	0.53
% admissions with operation	68.3	94.6	χ² = 46.33	<0.001
% with ASA class of first operation ⩾3	20.7	35.5	χ² = 18.45	<0.001
% with maximum complexity class of first operation ⩾5	32.9	46.5	χ² = 11.2	<0.001