Table 2.

The amount of available data varies significantly across the three different institutions

Hospital	Admissions (n)	Clostridium difficile cases (n)
First year (Apr 2011–Apr 2012)
A	11 380	82
B	14 675	161
C	39 467	426
Second year (Apr 2012–Apr 2013)
A	10 579	94
B	14 640	157
C	42 112	428

The outcome we consider occurs in about 1% of the population, resulting in low numbers of positive examples at smaller institutions.