Table 2

Population of the area of residence and the presence of CADM or anti-MDA-5 antibodies

CADM

α-MDA-5-positive

Population of area of residence (×1,000)

Total number of DM patients (M:F)

Mean age at onset (range)

Number (%) of patients (M:F)

P value*

Mean age at onset (range)

Number (%) of patients (M:F)

P value**

Mean age at onset (range)

T1 (0.5 to 108)

31 (4:27)

49.0 (4 to 70)

16 (51.6%) (1:15)

P for difference = 0.096

47.3 (4 to 69)

14 (45.2%) (1:13)

P for difference = 0.012

48.8 (20 to 66)

T2 (130 to 826)

26 (7:19)

44.0 (9 to 80)

10 (38.5%) (3:7)

P for trend = 0.031

40.0 (9 to 59)

7 (26.9%) (3:4)

P for trend = 0.003

39.9 (11 to 59)

T3 (2,200)

38 (17:21)

47.3 (1 to 79)

10 (26.3%) (4:6)

45.9 (1 to 73)

5 (13.2%) (1:4)

51.0 (39 to 63)

CADM, clinically amyopathic dermatomyositis; DM, dermatomyositis; M:F, male:female; MDA-5, melanoma differentiation-associated gene 5. *Prevalence of CADM in total DM. **Prevalence of anti-MDA-5 in total DM.

Muro et al. Arthritis Research & Therapy 2011 13:R214   doi:10.1186/ar3547