Table 3 Comparison of patients with and without postdischarge adverse outcomes on possible determinants (Leiden University Medical Centre, surgical patient admissions during 2003)

	Patients with postdischarge adverse outcomes (n = 487)	Patients without postdischarge adverse outcomes (n = 1473)	Statistical significance of difference
Average age at admission (SD)	54.3 (17.4)	52.4 (17.6)	t = −2.05, p = 0.04
Percentage males	52.8	53.7	χ² = 0.13, p = 0.72
Percentage with ASA class of 1st operation ⩾3	18.9	14.1	χ² = 6.43, p = 0.01
Percentage with maximum complexity class of 1st operation ⩾5	24.6	19.5	χ² = 5.92, p = 0.02
Percentage with in-hospital adverse outcomes	22.0	14.1	χ² = 16.72, p<0.01
Average duration (days) of admission (SD)	10.3 (17.6)	8.3 (13.0)	t = −2.64, p = 0.01