Heterogeneity of autoantibodies in 100 patients with autoimmune myositis: insights into clinical features and outcomes

Table 4 Demographics, associated autoantibodies, and distribution of 100 patients with autoimmune myositis according to the modified Peter and Bohan classification at diagnosis

	PM (n = 14)	DM (n = 23)	OM (n = 60)	CAM (n = 3)	P ^a
Age at diagnosis (years; mean ± SD)	52.7 ± 16.8	45.4 ± 16.7	45.6 ± 13.5	56.3 ± 11	0.303
Mean follow-up period (years; mean ± SD)	8.15 ± 4.8	12.52 ± 9.2	8.05 ± 6.1	7.64 ± 2.7	0.013
Associated autoantibodies
Anti-Ro (n = 31)	4 (28.6)	5 (21.7)	22 (36.7)	0	0.185
Anti-Ku (n = 23)	3 (21.4)	5 (21.7)	15 (25)	0	0.633
Anti-synthetases (n = 22)	3 (21.4)	4 (17.4)	15 (25)	0	0.463
Anti-U1RNP (n = 15)	0	2 (8.7)	13(21.7)	0	0.024^b
Anti-fibrillarin (n = 14)	0	1 (4.3)	13 (21.7)	0	0.007^c
Anti-La (n = 14)	1 (7.1)	3 (13)	10 (16.7)	0	0.394
SSc autoantibodies (n = 9)	0	1 (4.3)	8 (13.3)	0	0.081
Anti-PM-Scl (n = 9)	0	3 (13)	6 (10)	0	0.737
Anti-Mi-2-IPP (n = 3)	0	2 (8.7)	0	1 (33)^d	-
Anti-Mi-2-LIA (n = 3)	0	0	3 (5)	0	-
Anti-NUP (n = 3)	1 (7.1)	0	2 (3.3)	0	1
Anti-SRP (n = 2)	0	0	2 (3.3)	0	0.515
None (n = 20)	5(35.7)	6 (26.1)	7(11.7)	2 (66)	0.02^e

Unless otherwise specified, values are expressed as number (%). Anti-Ro was detected using addressable laser bead immunoassay; for anti-Mi-2-IPP and anti-Mi-2-LIA, autoantibody was present only by immunoprecipitation or line immunoassay. ^aFor Associated autoantibodies: to avoid more than 20% of values being <5, comparisons were made by Fisher's exact test between OM and all others. ^bOdds ratio 5.2, 95% confidence interval 1.1 to 24.7. ^cOdds ratio 10.8, 95% confidence interval 1.35 to 86. ^dThe patient also had a DM rash. ^eOdds ratio 0.27, 95% confidence interval 0.1 to 0.77. CAM, cancer-associated myositis; DM, pure dermatomyositis; OM, overlap myositis; PM, pure polymyositis; SD, standard deviation.

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