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Table 5 Cluster analysis variables compared across clusters in the validation sample a

From: OMERACT-based fibromyalgia symptom subgroups: an exploratory cluster analysis

Measure Cluster 1b(n = 116) Cluster 2c(n = 154) Cluster 3d(n = 100) Cluster 4e(n = 108) P-valuef
MFI physical fatigue 13.0 (3.9) 17.5 (2.3) 16.4 (2.7) 18.9 (1.8) <0.0001
MOS-Sleep problems Index II 46.1 (15.9) 52.9 (16.3) 68.5 (14.8) 74.1 (12.3) <0.0001
FIQ pain 4.8 (1.5) 7.1 (1.3) 6.7 (1.2) 8.5 (0.9) <0.0001
MASQ 82.7 (18.1) 91.3 (21.3) 107.0 (17.1) 112.8 (19.5) <0.0001
FIQ function 7.0 (4.8) 17.4 (5.2) 14.0 (5.2) 22.6 (3.5) <0.0001
FIQ stiffness 5.4 (2.2) 7.5 (1.8) 6.7 (2.2) 8.9 (1.0) <0.0001
GAD-7 5.0 (4.1) 5.0 (3.7) 14.2 (4.0) 13.0 (4.7) <0.0001
PHQ-9 8.6 (4.1) 9.5 (3.2) 17.1 (4.5) 17.4 (4.3) <0.0001
  1. aN = 478 total validation sample. Data are n (%). FIQ, Revised Fibromyalgia Impact Questionnaire; GAD-7, Generalized Anxiety Disorder 7-item scale; MASQ, Multiple Ability Self-report Questionnaire; MFI, Multidimensional Fatigue Inventory; MOS-Sleep Problems Index II, Medical Outcomes Study Sleep Scale; PHQ-9, Patient Health Questionnaire. bLow symptom intensity. cModerate symptoms, low negative mood. dModerate symptoms, higher negative mood and dyscognition. eHigh symptom intensity. fP-values are from the omnibus analysis of variance test across the four clusters. Pairwise comparisons between clusters also showed significant differences in all cases, except for the following: cluster 1 versus cluster 2 in regard to GAD-7 (P = 0.96) and PHQ-9 (P = 0.07) and cluster 3 versus cluster 4 with respect to PHQ-9 (P = 0.53).