Table 1.

Ordinal logistic regression assessing the factors associated with pain threshold. Crude and adjusted models are shown. For the adjusted OR we excluded EMS, HADS anxiety, ethnicity, swollen joint count, and sex as they showed no significant relationship with pain thresholds at the 0.05 level. HADS depression, tender joint count, patient global assessment, fatigue VAS, FACIT-F, and HAQ were all significantly correlated with pain threshold. However, many were also highly correlated with each other (e.g., tender point counts and tender joint counts; r = 0.71). We therefore excluded variables that showed strong collinearity with each other. Where strong collinearity existed we used both statistical and clinical assessments to decide which variables to include (for example, we chose tender point counts over tender joint counts).

FactorCrude OR (95% CI)pAdjusted OR (95% CI)p
Age0.97 (0.94, 0.99)0.0150.97 (0.94, 1.01)0.16
Disease duration0.97 (0.94, 1.00)0.0370.95 (0.91, 1.00)0.04
Pain (VAS)0.98 (0.97, 0.99)0.0020.99 (0.97, 1.01)0.38
No. tender points0.78 (0.71, 0.86)< 0.0010.75 (0.65, 0.86)< 0.001
Fatigue (VAS)0.97 (0.96, 0.99)< 0.0010.98 (0.96, 1.00)0.15
Health Assessment Questionnaire0.39 (0.23, 0.69)0.0011.19 (0.56, 2.56)0.64
ESR0.98 (0.96, 1.00)0.0351.00 (0.98, 1.03)0.83
FACIT-F1.04 (1.01, 1.08)0.011
Tender joint count0.88 (0.82, 0.93)< 0.001
Patient global assessment (VAS)0.98 (0.96, 0.99)0.003
HADS depression0.89 (0.81, 0.99)0.028
HADS anxiety0.92 (0.83, 1.01)0.064
Duration of morning stiffness, min1.00 (0.99, 1.00)0.076
White vs other ethnic groups1.52 (0.62, 3.74)0.360
Swollen joint count0.96 (0.86, 1.07)0.428
Male vs female0.67 (0.28, 1.61)0.373
  • EMS: early morning stiffness; HADS: Hospital Anxiety and Depression Scale; VAS: visual analog scale; ESR: erythrocyte sedimentation rate; FACIT-F: Functional Assessment of Chronic Illness Therapy-Fatigue scale; HAQ: Health Assessment Questionnaire.