Figure 4 Plots of the predicted probabilities as a function of rheumatoid factor (RF) titres in patients with at least one swollen joint at baseline. In this figure, we evaluated the effect of the baseline presence of at least one swollen joint on the interpretation of RF results. (A) We evaluated single continuous RF testing in patients with at least one swollen joint compared with the model from fig 3 (grey). (B) We evaluated a model of combined RF–anti‐citrullinated protein/peptide antibody testing calculated in the global population (grey, fig 3) compared with a model calculated in the subgroup of patients with at least one swollen joint at baseline (black). PepA, citrullinated peptide A; RA, rheumatoid arthritis.