Table 2.

Correlation among instruments in a cross-sectional setting.

	N of RAPID3 / instrument	RAPID3	PSAID12	SF-12 PCS	SF-12 MCS	BASDAI	FACIT-F	WLQ	Phys Global	Phys Arth	Swollen Joints	Tender Joints	Pain
PSAID12	207	0.90*
PSAID9	207	0.90*	1.00*
SF-12 PCS	270	−0.67*	−0.73*
SF-12 MCS	270	−0.41*	−0.48*	0.11
BASDAI	205	0.88*	0.87*	−0.68*	−0.42*
FACIT-F	188	−0.77*	−0.84*	0.71*	0.54*	−0.78*
WLQ**	141	0.67*	0.72*	−0.63*	−0.50*	0.68*	−0.76*
Phys Global	304	0.63*	0.63*	−0.50*	−0.26*	0.56*	−0.48*	0.45*
Phys Arth	306	0.60*	0.56*	−0.45*	−0.22*	0.49*	−0.42*	0.38*	0.84*
SwollenJoints	231	0.39*	0.39*	−0.28*	−0.17*	0.34*	−0.26*	0.25*	0.54*	0.68*
TenderJoints	231	0.42*	0.37*	−0.33*	−0.15*	0.35*	−0.28*	0.29*	0.55*	0.63*	0.77*
Pain	344	0.94 *	0.89*	−0.63*	−0.34*	0.85	−0.72	0.62	0.64	0.61	0.39	0.41
Global	343	0.93 *	0.83*	−0.62*	−0.42*	0.81	−0.72	0.64	0.56	0.55	0.35	0.38	0.83*

Spearman’s correlation coefficients are shown in this table. Yellow indicates a strong correlation (rho 0.8-1.0) and blue a moderate correlation (0.6-0.79).

^*p-value <0.05

^**The productivity score of the Work Limitations Questionnaire is shown here. The WLQ index had nearly identical coefficients.

In Italics: Note that pain and global assessment are part of the RAPID3 so the correlation is expected to be high.

Note that the additional columns with the other outcomes were not part of the original hypotheses.

Additional Abbreviations: RAPID3=Routine Assessment of Patient Index Data 3 ;PSAID12=Psoriatic Arthritis Impact of Disease 12-question version; PSAID9=Psoriatic Arthritis Impact of Disease 9-question version; SF-12 PCS = Short Form 12 Physical Component Score; SF-12 MCS = Short Form 12 Mental Component Score; BASDAI = Bath Ankylosing Spondylitis Disease Activity Index; Phys global and Phys arth refer to the physician global assessments for overall health and arthritis respectively.