Varying the item format improved the range of measurement in patient-reported outcome measures assessing physical function

Table 2 Psychometric results for the experimental items presented in three different item formats

Item	Format^b	Content	Slope	Threshold^c						Item fit: p (S-X ²)^d	I_max (at T-score)^e	Area under the curve^f	Percentage floor/percentage ceiling^g
Item	Format^b	Content	Slope	1	2	3	4	5	Mean	Item fit: p (S-X ²)^d	I_max (at T-score)^e	Area under the curve^f	Percentage floor/percentage ceiling^g
A1	A	Do 2 hours of physical labor	3.49	38.6	42.9	47.8	54.9		46.1	0.6523	3.71 (T = 42)	92.9	10.4/41.6
B1^a	B		4.53	38.0	43.0	48.4	53.1		45.6	0.1133	5.93 (T = 49)	132.9	10.0/42.7
C1	C		4.01	37.7	42.0	46.3	52.7	59.8	47.7	0.0358	4.88 (T = 42)	140.3	10.2/19.6
A2^a	A	Do yard work	4.09	36.3	40.1	44.3	50.7		42.9	0.1473	5.10 (T = 40)	111.1	6.6/57.3
B2	B		4.79	35.7	40.8	46.1	50.6		43.3	0.0751	6.58 (T = 47)	144.0	6.7/52.7
C2	C		4.53	34.3	39.1	43.1	49.3	56.0	44.4	0.0300	6.10 (T = 40)	167.5	5.3/32.1
A3	A	Climb several flights of stairs	3.78	35.2	40.3	45.2	52.0		43.2	0.1722	4.28 (T = 41)	107.0	5.8/51.5
B3^a	B		4.20	34.2	40.8	46.7	51.3		43.3	0.8460	5.16 (T = 48)	126.0	5.1/51.3
C3	C		3.78	33.3	39.8	44.0	51.0	57.1	45.0	0.1174	4.31 (T = 42)	135.0	6.3/25.4
A4^a	A	Go for a walk of at least 15 minutes	3.78	33.2	36.4	40.2	45.5		38.8	0.2497	4.45 (T = 37)	91.3	3.7/73.5
B4	B		4.03	32.1	37.2	42.0	45.8		39.3	0.3555	4.93 (T = 43)	107.0	3.4/71.6
C4	C		3.99	30.3	35.6	39.5	44.9	50.8	40.2	0.0033	4.85 (T = 37)	134.7	3.6/47.5
A5^a	A	Open previously opened jars	1.91	18.8	28.4	37.9			28.4	0.2434	1.10 (T = 28)	36.5	0.9/85.8
B5	B		1.90	12.9	22.8	32.3	39.6		26.9	0.5429	1.10 (T = 33)	39.9	0.3/81.9
C5	C		1.57	5.0	15.5	23.4	34.0	45.4	24.7	0.1877	0.77 (T = 20)	33.6	0.3/62.4

^aItem is part of the final Patient Reported Outcomes Measurement Information System Physical Function (PROMIS PF) item bank version 1.0. ^bFormat A: “Are you able to …” (five-category response scale from “Without any difficulty” to “Unable to do”); format B: “Does your health now limit you in …” (five-category response scale from “Not at all” to “Cannot do”); format C: “How difficult is it for you to …” (six-category response scale from “Very easy” to “Impossible”). ^cThresholds are transformed to a T-score of 50 ± 10, where 50 = mean and 10 = standard deviation of the analytic sample; slopes are reported unchanged. ^d X ² statistics (S-X ²) were evaluated after adjusting for multiple testing (p < 0.0033). ^eI_max (at T-score) depicts the maximum of item information (upper number) of a given item at the corresponding point on the T-score continuum. ^fTotal area under the item information curve (IIC) on the empirically observed T-score range in the calibration sample (T-score = 11.1–73.6). ^gPercentage of participants who answered the item with the lowest (floor) or highest (ceiling) possible response category

ISSN: 1478-6362