Heat map of the cluster analysis of 318 anti-CCP-negative RA patients. Heat map representing the presence or absence of disease characteristics in individual patients. To make variables comparable, all values were transformed into binary values. For those variables on a continuous scale, the following cut-offs were made: Morning Stiffness, ≤60 minutes; Fatigue, fatigue rated more than mean (45.1) on Visual Analogue Scale; symptom duration more than or ≤12 weeks age at inclusion, age greater than mean age (59.2 years); swollen joint count, more than four swollen joints; CRP, CRP greater than reference value (10 mg/L). The dendrograms depict the relative strength of correlations between the variables and the patients, respectively. CCP, citrullinated peptide antibody; CRP, C-reactive protein; RA, rheumatoid arthritis; SJC, swollen joint count; VAS, visual analogue scale.