Table 3.

Counts of discordant pairs for two outcomes and their combination, with McNemar P-values, and Gart’s test for interaction with type. There are 2298 pairs, 1354 pairs that finely balance the 47 hospitals (type 1) and 944 pairs that contrast hospitals with different usual practices (type 2). Only discordant pairs are recorded here. For readmission, there were 13 deaths within 30 days, 6 with general anesthesia, 7 with regional anesthesia, and these are included in the unfavorable outcome category in each comparison.

	Alive without deep vein thrombosis
	All	Finely Balanced Pairs (type 1) Usual Practice Pairs (type 2)
General	72	42	30
Regional	100	66	34
P-value	0.040	0.027	0.708
Odds Ratio (OR)	1.39	1.57	1.13
95% CI for OR	[1.03, 1.88]	[1.07, 2.31]	[0.69, 1.85]
P-value for interaction		0.34
	Alive without readmission at 30 days
	All	Finely Balanced Pairs (type 1) Usual Practice Pairs (type 2)
General	106	61	45
Regional	135	84	51
P-value	0.071	0.068	0.610
Odds Ratio (OR)	1.27	1.38	1.13
95% CI for OR	[0.99, 1.64]	[0.99, 1.91]	[0.75, 1.69]
P-value for interaction		0.51
	Alive without both deep vein thrombosis and readmission at 30 days
	All	Finely Balanced Pairs (type 1) Usual Practice Pairs (type 2)
General	152	84	68
Regional	200	128	72
P-value	0.012	0.003	0.800
Odds Ratio (OR)	1.32	1.52	1.06
95% CI for OR	[1.07, 1.62]	[1.16, 2.01]	[0.76, 1.47]
P-value for interaction		0.10