Levels of anti-citrullinated protein antibodies and IgM rheumatoid factor are not associated with outcome in early arthritis patients: a cohort study

Table 2 The relation between IgM-RF status and levels and outcome variables

	Correlation of IgM-RF levels at baseline^#	P ¹	IgM-RF positive at baseline (n = 255)^$	IgM-RF negative at baseline (n = 280)^$	P ²
IgM-RF level at baseline (IU/ml), median (IQR)	x		100 (60-200)	10 (6-14)
IgM-RF level at 1 year (IU/ml), median (IQR)	x		51 (23-97)	9 (5-10)
DAS28 at baseline	0.11	0.01	4.88 (1.19)	1.66 (1.29)	0.01
HAQ at baseline	0.01	0.79	1 (0.5-1)	0.94 (0.5-1.5)	0.49
SHS at baseline	0.11	0.02	0 (0-1)	0 (0-0)	0.00
DAS28 at 2-year follow-up	0.17	0.69	2.92 (1.30)^&	2.84 (1.23)^&	0.58
HAQ at 2-year follow-up	0.04	0.41	0.5 (0-0.88)	0.38 (0-0.88)	0.43
SHS at 2-year follow-up	0.22	0.00	2 (0-9)	0 (0-4)	0.00

^#Spearman correlation ^$Median with IQR unless stated otherwise^&Mean with SD P-value of correlation² P-value IgM-RF positive versus IgM-RF negative.
DAS = disease activity score; HAQ = Health Assessment Questionnaire; Ig = immunoglobulin; IQR = interquartile range; RF = rheumatoid factor; SD = standard deviation; SHS = Sharp-van der Heijde score.

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