Empirically derived subgroups in rheumatoid arthritis: association with single-nucleotide polymorphisms on chromosome 6

Table 1 Cluster characteristics and differences between clusters

Trait	Cluster 2	Cluster 3	Cluster 4	Cluster 5
Rheumatoid arthritis (% affected)	44.4	99.1	99.8	100
Anti-CCP	*^a	52.3	124.8³	127.8³
Rheumatoid factor	*	33	111^2,3	138^2,3
Joint alignment and motion score	*	5	21.5³	65^2,3,4
Age at onset (median)	36	42^2,5	40^2,5	32
Female (%)	69.1	74.7	74.1	84.5
BMI (median)	24.0	26.6⁵	25.1	24.8
Subcutaneous nodules (%)	16.3	22.4	54.4	68.0
R/L hand erosions (%)	*	73.5	100	100
Severity R/L hand (5-point scales)	*	2	3³	5^2,3,4
Tender joint count	*	4	6³	6³
Swollen joint count	*	5	8³	8³

Superscripts indicate clusters compared to which the column cluster is significantly higher. For example, the JAM score for Cluster 5 is significantly higher than Clusters 2, 3, and 4.
*^a, Data are missing for the majority of this cluster.

ISSN: 1753-6561