Table 1.

Characteristics of studies included.

		Non-IBD diseases
Characteristics	IBD	Total (RA+Ps/PsA)	RA	Ps/PsA	Difference between 3 diseases (P-value)
Total No. of articles	58	268	172	96	–
Total No. of patients	4,194	124,682	95,849	28,833	–
Male/female	2,032/2,162	63,252/61,430	48,925/46,924	14,327/14,506	–
Year of publication (No. of articles)					0.175
Before 2000	10	52	39	13
After 2000	48	216	133	83
Region of study (No. of articles)					<0.001
Europe	35	107	58	49
North America	17	66	52	14
Asia	4	88	57	31
Oceania	2	3	3	0
Africa	0	3	1	2
South America	0	1	1	0
Study design (No. of articles)					<0.001
Prospective	14	159	103	56
Retrospective	44	109	69	40
Type of population (No. of articles)					<0.001
Adult	47	262	169	93
Children	11	6	3	3
Sample size (No. of articles)					<0.001
≤ 100	46	114	53	61
>100	12	154	119	35
Administration pathway of MTX					<0.001
Intramuscularly	11	8	4	4
Orally	10	117	69	48
Subcutaneously	14	5	1	4
Intravenously	1	0	0	0
Combination	18	27	17	10
a Dose of MTX (No. of articles)					<0.001
Low dose	19	160	103	57
High dose	38	92	60	32
Mean/median duration of MTX treatment (No. of articles)					0.067
Short term (≤ 2 years)	46	191	120	71
Long term (2–4 years)	10	39	29	10
Very long term (>4 years)	0	29	19	10
b Usage of steroid (No. of articles)					<0.001
No	8	54	44	10
Yes	40	67	63	4
c Usage of folic acid (No. of articles)					0.631
No	6	21	16	5
Yes	33	122	80	42
NOS score (No. of articles)					0.803
5	2	15	11	4
6	41	185	118	67
7	1	3	3	0
8	8	49	30	19
9	6	16	10	6

^aFor the dose of MTX, low dose is defined as mean/median weekly dose ≤ 15 mg or 12.5 mg/m², and cumulative dose ≤ 1.5 g; high dose is defined otherwise.

^bFor the usage of steroid, <50% patients receiving steroid is considered as No; otherwise Yes.

^cFor the usage of steroid, <50% patients receiving folic acid is considered as No; otherwise Yes.

IBD, inflammatory bowel disease; RA, rheumatoid arthritis; Ps, psoriasis; PsA, psoriatic arthritis; MTX, methotrexate; NOS, Newcastle-Ottawa Scale.