Discriminant validity, responsiveness and reliability of the rheumatoid arthritis-specific Work Productivity Survey (WPS-RA)

Table 3 WPS-RA baseline responses by HAQ-DI and SF-36: work productivity of employed subjects in the modified intent-to-treat population

Instrument^a	Number of days of work missed over the previous month, mean (SD)		Number of days with productivity ≤ 50% at work over the previous month, mean (SD)		Rate of arthritis interference with WP^b over the previous month, mean (SD)
	Worst	Best	Worst	Best	Worst	Best
HAQ-DI (cutoff 0.5 and 1.5)	3.0 (7.19)	1.1^c (3.45)	6.8 (8.96)	3.4^c (6.88)	4.8 (2.77)	4.4^d (2.67)
	n = 46	n = 35	n = 46	n = 35	n = 46	n = 35
SF-36 PCS (cutoff 21.76 and 35.26)	2.9 (6.96)	1.3^e (4.50)	8.7 (10.02)	2.2^c (4.60)	6.0 (2.13)	3.5^c (2.16)
	n = 21	n = 20	n = 21	n = 20	n = 21	n = 20
SF-36 MCS (cutoff 38.36 and 54.67)	4.1 (8.07)	0.7^c (1.59)	10.6 (11.07)	4.0^c (7.83)	5.2 (2.89)	4.1^c (2.47)
	n = 20	n = 21	n = 20	n = 21	n = 20	n = 21

^aCutoff points represent first and third quartiles of baseline scores; 'worst' group (HAQ-DI score ≥ third quartile; SF-36 score ≤ first quartile) and 'best' group (HAQ-DI score ≤ first quartile, SF-36 ≥ third quartile). ^bScore on a scale of 0 to 10 points (0 = no interference and 10 = complete interference). WPS-RA recall period is 1 month. ^cP value ≤ 0.001, ^dP value < 0.01, ^eP value ≤ 0.05 best versus worst; P values were obtained using the non-parametric bootstrap-t method. HAQ-DI, Health Assessment Questionnaire – Disability Index; SD, standard deviation; SF-36, Short Form-36 health survey; SF-36 MCS, Short Form-36 health survey – Mental Component Summary; SF-36 PCS, Short Form-36 health survey – Physical Component Summary; WP, work productivity; WPS-RA, Work Productivity Survey – Rheumatoid Arthritis.

ISSN: 1478-6362