Table 1.

Characteristics of included studies evaluating the association between the 5-HTTLPR polymorphism and the presence of IBS

Author	Year	Location	Ethnicity	Case and control selection	SNP method	HWE test
Pata C [20]	2002	Turkey	Turkish	Case: patients diagnosed with Rome I criteria	AS-PCR
				Control: healthy volunteers without detailed descriptions of matching methods		P = 0.0196
Lee DY [21]	2004	Korea	East Asian	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.8526
Kim HJ [12]	2004	USA	Mostly Caucasian	Case: patients selected from a database of 752 patients with IBS	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.9564
Wang BM [22]	2004	China	East Asian	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy contrtols matched for age and gender		P = 0.1693
Yeo A [10]	2004	North America	Caucasian	Case: patients diagnosed with Rome I criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.7053
Zhang XM [23]	2006	China	East Asian	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy controls matched for age and gender		P = 0.9536
Park JM [11]	2006	Korea	East Asian	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.1976
Whitehead WE [24]	2006	USA	Mostly Caucasian	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.2376
Li Y [25]	2007	China	East Asian	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.5862
Saito YA [26]	2007	USA	Mostly Caucasia	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: no IBS patients matched for age, race and gender		P = 0.2372
Camilleri M [27]	2008	USA	Mostly Caucasian	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		NC
Kohen R [28]	2009	USA	Mostly Caucasia	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy volunteers matched for age, race and gender		P = 0.1479
Schmulson M [29]	2009	Mexico	Mexican	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.0000
Niesler B [30]	2010	UK	Caucasian	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy volunteers without detailed descriptions of matching methods		P = 0.5492
Sikander A [31]	2009	India	Indian	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy controls without detailed description of matching methods		P = 0.4341
Markoutsaki T [32]	2011	Greek	Caucasian	Case: patients diagnosed with Rome III criteria	PCR-RFLP
				Control: healthy volunteers without detailed description of matching methods		P = 0.6973
Jiang ZD [33]	2012	USA	Mostly Caucasian	Case: patients diagnosed with Rome II criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.1063
Wang YM [34]	2012	China	East Asian	Case: patients diagnosed with Rome III criteria	AS-PCR
				Control: healthy controls without detailed description of matching methods		P = 0.0000
Park CS [35]	2012	Korea	East Asian	Case: patients diagnosed with Rome III criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.3054
Zhang ZX [36]	2012	China	East Asian	Case: patients diagnosed with Rome III criteria	AS-PCR
				Control: healthy volunteers matched for age, race and gender		P = 0.4531
Kumar S [37]	2012	India	Indian	Case: patients diagnosed with Rome III criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.3093
Saito YA [38]	2012	USA	Mostly Caucasia	Case: patients diagnosed with Rome III criteria	AS-PCR
				Control: healthy examinees matched for age, race and gender		P = 0.5924
Colucci R [39]	2013	Italy	Caucasian	Case: patients diagnosed with Rome III criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.6459
Shiotani A [40]	2013	Japan	East Asian	Case: patients diagnosed with Rome III criteria	AS-PCR
				Control: healthy controls without detailed descriptions of matching methods		P = 0.5780
Farjadian S [41]	2013	Iran	Iranian	Case: patients diagnosed with Rome III criteria	AS-PCR
				Control: healthy examinees matched for age, race and gender		P = 0.2284

SNP: single nucleotide polymorphism; PCR-RFLP: polymerase chain reaction-restriction fragment length polymorphism; AS-PCR: allele-specific polymerase chain reaction; HWE test: Hardy-Weinberg equilibrium test; NC: not able to calculated from raw data.