Improved responsiveness and reduced sample size requirements of PROMIS physical function scales with item response theory

Table 1 Physical function instruments, baseline, 12-month, and change scores

					Change Scores (12 months - Baseline)
	Items (n)	Response options (n)	Baseline mean ± SD¹	12-Months Mean ± SD	Mean	SD (95% CL² for SD)	P-value ³
Legacy PF-10	10	3	47.2 ± 29	49.0 ± 29	1.8	18.4 (16.5, 20.2)	0.04
Legacy HAQ	20	4	29.2 ± 23	30.7 ± 24	1.5	10.6 (9.4, 11.8)	0.002
Item-Improved PF-10	10	5	41.5 ± 26	43.0 ± 27	1.5	16.3 (13.9, 18.6)	0.05
Item-Improved HAQ	20	5	21.0 ± 21	22.1 ± 21	1.1	8.6 (7.7, 9.6)	0.01
PROMIS PF 10	10	5	33.9 ± 22	35.2 ± 23	1.3	11.1 (10.0, 12.2)	0.01
PROMIS PF 20	20	5	30.6 ± 21	31.8 ± 22	1.2	9.4 (8.4, 10.1)	0.01

¹ Standard Deviation, ² Confidence Limits, ³ Pair-wise t-test.
HAQ, health assessment questionnaire; Item-Improved, Changes to items intended to improve their performance by altering parameters such as time frame and response options while retaining the same item stem; PF, physical function; PROMIS, Patient-Reported Outcomes Measurement Information System.

ISSN: 1478-6362