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
| Oedema | Atrophy | Fatty replacement | Fascial 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) | ||||
| Black | 8.41 (−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 races | 6.18 (−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.