Table 2.

Principal component analysis; component matrix

	C1	C 2	C3	C 4
PDQ	0.703	0.422	− 0.572	0.001
NP	0.881	− 0.411	0.045	0.229
TBP	0.899	− 0.361	0.070	− 0.236
PP	0.639	0.610	0.468	0.014

Method of extraction: principal component analysis

Four components were extracted

C component, PDQ pain detection questionnaire, NP nocturnal pain, TBP total back pain, PP peripheral pain