Table 4

Multivariate analysis of the extent of the different thigh MRI features (percentage of muscles involved) in patients with anti-HMGCR-associated myositis compared with those with anti-SRP-associated myositis using fractional probit regression

OedemaAtrophyFatty replacementFascial oedema
dy/dx (95% CI)dy/dx (95% CI)dy/dx (95% CI)dy/dx (95% CI)
IMNM autoantibody group (anti-SRP vs anti-HMGCR)6.92 (−9.74 to 23.58)19.18 (6.52 to 31.84)**17.64 (0.59 to 34.70)*6.59 (−1.38 to 14.56)
Age at onset (10 years)−2.04 (−7.33 to 3.25)0.28 (−4.69 to 5.25)0.06 (−5.53 to 5.65)1.35 (−1.85 to 4.56)
Time from onset to MRI (logarithm of months)−21.98 (−35.02 to −8.93)***11.21 (−2.96 to 25.38)20.50 (6.34 to 34.66)**−2.32 (−9.08 to 4.45)
Sex (female)−10.63 (−26.29 to 5.04)5.06 (−8.39 to 18.50)−2.68 (−17.65 to 12.30)−6.19 (−13.14 to 0.76)
Race (referenced to white patients)
 Black8.41 (−8.93 to 25.75)4.42 (−8.56 to 17.40)11.98 (−4.41 to 28.37)−4.47 (−10.05 to 1.10)
 Other races6.18 (−16.62 to 28.97)16.62 (−11.24 to 44.48)−24.72 (−48.05 to −1.39)*−3.18 (−9.81 to 3.45)
  • dy/dx, marginal effect (% change of the dependent variable for each one point of the predictor variables).

  • Multivariate analysis adjusted for treatment (administration of corticosteroid, intravenous immunoglobulins, rituximab, mycophenolate, methotrexate or azathioprine).

  • *<0.05; **<0.01; ***<0.001.

  • HMGCR, HMG-CoA reductase; IMNM, immune-mediated necrotising myopathy; SRP, signal recognition particle.