Table 1

Prognostic factors of death, disability, muscle strength and persistent immunosuppressive treatment

		Full model		Final model
	n	Predictor	HR/OR (95% CI)	Predictor	HR/OR (95% CI)	ROC area (95% CI)	HR/OR after bootstrapping
CTD, connective tissue disorder; DM, dermatomyositis; final model, multivariate analysis with p<0.05; full model, multivariate analysis with p<0.25; MRC, Medical Research Council; PM, polymyositis (defined by endomysial cell infiltrates); ROC, receiver operating characteristic; Unsp myositis, unspecified myositis (clinical PM, with perimysial and perivascular cell infiltrates).
*In 8 of the 161 patients, the cause of death was unknown and in 5 patients, information on disease duration before was missing; these patients were excluded from the analysis.
†Two missing values.
‡Twelve missing values.
Disease-related mortality	148^*	Malignancy	7.4 (1.4 to 38.1)	Malignancy	7.8 (1.5 to 40.4)	—	6.0
		Interval from clinical manifestation to treatment <6 months	7.6 (1.0 to 57.3)	Interval from clinical manifestation to treatment <6 months	7.7 (1.0 to 58.0)		5.9
		Age >60 years	2.7 (1.0 to 7.3)	Age >60 years	2.7 (1.0 to 7.5)		2.4
		Unsp myositis and CTD	0.4 (0.06 to 3.2)
Disability (Rankin score ⩾3)	108†	Male sex	3.2 (1.1 to 9.1)	Male sex	3.1 (1.2 to 7.9)	0.6 (0.5 to 0.7)	2.0
		Age >60 years	2.1 (0.6 to 7.0)
		Interval from clinical manifestation to treatment >6 months	2.6 (0.9 to 7.3)
		DM	0.5 (0.1 to 1.6)
		Unsp myositis	2.4 (0.7 to 8.1)
		Duration of follow-up (years)	0.9 (0.8 to 1.0)
Muscle strength	110	Male sex	2.6 (0.9 to 7.0)			0.6 (0.5 to 0.7)
(MRC <128)		Age >60 years	3.4 (1.1 to 10.3)	Age >60 years	3.6 (1.3 to 10.3)		2.3
		Unsp myositis and CTD	0.3 (0.03 to 2.1)
		PM	2.5 (0.4 to 14.0)
Persistent treatment	98‡	Jo-I	4.1 (1.2 to 14.1)	Jo-I	4.4 (1.3 to 15.0)	0.7 (0.6 to 0.8)	3.1
		PM	0.3 (0.04 to 3.1)	Duration of follow-up (years)	0.9 (0.8 to 1.0)		0.9
		Duration of follow-up (years)	0.9 (0.8 to 1.0)