. 2021 Mar 22;21:132. doi: 10.1186/s12876-021-01621-y

Table 2.

Binary recoding schema of the SCCAI for IRT analysis

Items	SCCAI Score^a		Binary score
Item 1 Daytime frequency	0		0
Item 1 Daytime frequency	1–3		1
Item 2 Nocturnal frequency	0		0
Item 2 Nocturnal frequency	1–2		1
Item 3 Urgency	0–1		0
Item 3 Urgency	2–3		1
Item 4 Blood in stool	0		0
Item 4 Blood in stool	1–3		1
Item 5 General well-being	0–1		0
Item 5 General well-being	2–4		1
Item 6 Extra-intestinal manifestations	Arthritis (new Item 6)	Yes/no	1/0
	Uveitis (new Item 7)	Yes/no	1/0
	Erythema nodosum (new Item 8)	Yes/no	1/0
	Pyoderma gangrenosum (new Item 9)	Yes/no	1/0

SCCAI Simple Clinical Colitis Activity Index

^aThe SCCAI Score for each item is derived from Table 1