Adaptation of Chinese and English versions of the Ankylosing Spondylitis quality of life (ASQoL) scale for use in Singapore

Table 4 Rasch item statistics for Singapore ASQoL

Item	Item Calibration in logits (SE)	INFIT (MNSQ)	OUTFIT (MNSQ)	DIF Probability by Mantel-Haenszel statistics (p)
Item	Item Calibration in logits (SE)	INFIT (MNSQ)	OUTFIT (MNSQ)	Gender	Age^a	Language^b
#1	−0.64 (0.20)	1.14	1.25	0.4381	0.0074	0.7937
#2	0.48 (0.23)	0.99	0.89	0.0005	0.9200	0.5870
#3	1.56 (0.30)	1.08	0.93	0.5964	0.0037	0.6836
#4	0.63 (0.24)	0.80	0.69	0.9713	0.2586	0.9458
#5	1.09 (0.26)	0.87	0.78	0.7520	0.0476	0.9763
#6	−0.51 (0.20)	1.07	1.14	0.6056	0.8955	0.1197
#7	−0.58 (0.20)	0.95	0.87	0.0476	0.2484	0.0850
#8	−0.85 (0.20)	0.78	*0.68*	0.5995	0.9560	0.8635
#9	1.02 (0.26)	0.90	0.72	0.5301	0.5218	0.1634
#10	0.32 (0.23)	0.94	1.01	0.0631	0.9597	0.1467
#11	1.94 (0.33)	1.09	0.95	0.5933	0.6896	0.3634
#12	−1.61 (0.20)	0.86	0.74	0.1651	0.0992	0.0293
#13	−0.55 (0.20)	0.89	0.97	0.4904	0.1512	0.6042
#14	−1.69 (0.20)	*1.45*	*1.66*	0.7045	0.6147	0.0397
#15	−0.51 (0.20)	0.92	0.82	0.6857	0.2089	0.0286
#16	2.44 (0.38)	1.00	1.29	0.4703	0.0555	0.1191
#17	−1.31 (0.20)	1.13	1.12	0.4670	0.9162	0.9222
#18	−1.23 (0.20)	1.04	0.95	0.5116	0.2195	0.7969

Bold italics = MNSQ values outside range of 0.7 to 1.3. Italics = Bonferroni adjusted p < 0.0027 (denote concern of DIF)
INFIT information-weighted fit statistics, OUTFIT outlier-sensitive statistics, MNSQ mean square, DIF differential item functioning
^aAge < 50 years vs. ≥50 years; ^bChinese vs. English

ISSN: 1471-2474