Table 2 Estimated risk of antibiotic-associated diarrhea, proportion of patients tested for diarrhea associated with Clostridium difficile and adjusted risk of C. difficile-associated diarrhea in the probiotic and placebo groups*

Author, year	Risk of AAD, no. of patients/ total no. of patients (%)		CDAD testing, no. of patients/total no. (%) with AAD		Risk of CDAD among those tested† (%)		Adjusted risk of CDAD, %‡
Author, year	Probiotic	Placebo	Probiotic	Placebo	Probiotic	Placebo	Probiotic	Placebo
Ouwehand et al.,²⁴ 2014	33/168 (19.6) 21/168 (12.5)	41/167 (24.6)	33/33 (100) 21/21 (100)	41/41 (100)	3/33 (9.1) 3/21 (14.3)	8/41 (19.5)	1.8	4.8
Allen et al.,¹⁰ 2013	159/1493 (10.6)	153/1488 (10.3)	93/159 (58.5)	88/153 (57.5)	12/93 (12.9)	17/88 (19.3)	1.4	2.0
Selinger et al.,²⁵ 2013	5/117 (4.3)	10/112 (8.9)	5/5 (100)	4/10 (40.0)	0/5 (0)	0/4 (0)	0	0
Gao et al.,²⁰ 2010	13/86 (15.1) 24/85 (28.2)	37/84 (44.0)	13/13 (100) 24/24 (100)	37/37 (100)	1/13 (7.7) 8/24 (33.3)	20/37 (54.1)	5.3	23.8
Sampalis et al.,²⁶ 2010	47/216 (21.8)	65/221 (29.4)	16/47 (34.0)	30/65 (46.2)	1/16 (6.2)	4/30 (13.3)	1.4	3.9
Safdar et al.,²⁷ 2008	4/23 (17.4)	6/17 (35.3)	3/4 (75.0)	4/6 (66.7)	0/3 (0)	1/4 (25.0)	0	8.8
Beausoleil et al.,²⁸ 2007	7/44 (15.9)	16/45 (35.6)	2/7 (28.6)	13/16 (81.2)	1/2 (50.0)	7/13 (53.8)	8.0	19.1
Hickson et al.,²⁹ 2007	7/69 (10.1)	19/66 (28.8)	7/7 (100)	19/19 (100)	0/56 (0)	9/53 (17.0)	0	13.6
Plummer et al.,³⁰ 2004	15/69 (21.7)	15/69 (21.7)	15/15 (100)	15/15 (100)	2/15 (13.3)	5/15 (33.3)	2.9	7.2
Heimburger et al.,³¹ 1994	5/16 (31.2)	2/18 (11.1)	5/5 (100)	2/2 (100)	0/5 (0)	0/2 (0)	0	0

Note: AAD = antibiotic-associated diarrhea, CDAD = Clostridium-difficile-associated diarrhea.

*Some studies had 2 probiotic groups.

†The denominator is the number of patients with AAD who were tested for CDAD. Values are before adjustment for missing data.

‡Obtained by multiplying the risk of AAD by the risk of CDAD among those tested, under the assumption that the missing test results were missing at random.