Table 7.

Chracteristics of the included studies of 5-HT in this meta-analysis

References	Year	Location	n, IBS	n, Control	IBS diagnosis	Control Composition	Age, IBS (range, $\overline{\text{x}}+\text{s}$)	Female IBS, n	Age, HC (range, $\overline{\text{x}}+\text{s}$)	Female HC, n	Sample	Technique
Yu et al. [30]	2016	China	30	30	Not reported	Healthy controls	39 ± 21	14	42.5 ± 19.5	15	Serum	HPLC
Dunlop et al. [31]	2005	Britain	15	15	Rome II	Healthy controls	35.1 ± 2.9	15	35.9 ± 2.6	10	Plasma	HPLC
Thijssen et al. [32]	2015	Netherlands	154	137	Rome III	Healthy controls	44.5 ± 16.3	108	44.2 ± 19.3	84	Plasma	HPLC
Park et al. [29]	2009	Korea	21	13	Rome II	Healthy controls	24–78	13	29–68	6	Plasma	HPLC
Keszthelyi et al. [33]	2013	Netherlands	15	15	Rome III	Healthy controls	44 ± 13	8	33 ± 17	10	Plasma	HPLC

5-HT, 5-hydroxytryptamine; IBS, irritable bowel syndrome; HC, healthy control; HPLC, high-pressure liquid chromatography