Table 1:

Characteristics of clinical studies meeting inclusion criteria

Author, Year	Study Design	Country/Study Period	Prevalence HP (%)	Total, N	IBD, N	CD, N	UC, N	Controls, N	Mean Age, IBD	Mean Age, Control	Sex (%, Female)	HP Prevalence, Control (%)	HP Prevalence, IBD (%)
Lord, 2018a	Cross Sectional	Australia 1996-2009	10.8	704	447	212	235	257	29.9 (SD ±13.2)	57.2 (SD +13.5)	53.8	13.2	9.4
Rosania, 2018	Case-Control, age and sex-matched	Germany 2016-2017	24.7	381	127	90	37	254b	42 (SD ±12)	41 (SD ±12.4)	53.3c	28.7	16.5
Wagtmans, 1997e	Case-control, age-matched	Netherlands 1974-1975	21.9	663	386	386	0	277	37	36.9	44.9	35.4	12.2

^aThis study included H. pylori (HP) positive, trace, and negative samples. No information was provided delineating positive from trace positive, but the study considered trace to be a “non-positive” result. Accordingly, we considered “trace” to be HP negative for this analysis.

^bRosania et al included control groups for each set: CD, UC, and IBD. 254 was the number of controls for the IBD group. Separate UC and CD control groups contained 180 and 74, respectively.

^cOverall breakdown of sex was calculated using IBD group added to control group for IBD. Each subset, UC and CD, was compared to separate controls not included in this calculation. In addition, this study contained an error in its tables where totals for sex for IBD was reversed. This was corrected in our calculation and the authors were contacted.

^dSerologic evidence included ELISA and/or Western Blot immunoassays

^eThis study only included patients with CD and not UC. Therefore, IBD total is equal to CD total.

^fBoth IgG and IgA were tested. However, CagA was only tested in the samples where IgG was positive. In addition, the study determined seroprevalence by IgG alone and not IgA positivity. Therefore, IgA positivity was not included for this analysis.