The physician global disease activity (MDGA) and patient global disease activity (PDGA) are both required components of the IMACS core outcome set for inflammatory myopathy. Each is a 0–10 visual analogue scale (or numerical rating scale). Both are used in the 2016 ACR/EULAR myositis response criteria alongside MMT-8, HAQ-DI, muscle enzymes, and extramuscular disease activity.
Both the MDGA and PDGA are 0–10 visual analogue or numerical rating scales that capture the global disease activity of inflammatory myositis from different perspectives. They are both required components of the IMACS core outcome set and are used in the calculation of the 2016 ACR/EULAR myositis response criteria (minimal, moderate, and major improvement).
In the IMACS response criteria, improvement in MDGA counts as one of the six core outcome measures, and the PDGA counts as another. For minimal improvement, at least 3 of 6 measures must improve by 20% or more, with no more than 2 measures worsening by more than 25%.
The physician and patient global assessments often diverge - particularly in patients with muscle damage (atrophy, contractures) or those with fatigue-dominant presentations where subjective burden exceeds objective findings. This discordance is clinically important and should prompt further evaluation.
The global disease activity VAS assessments were established as part of the IMACS core outcome set by Miller, Rider, and colleagues, published in Rheumatology in 2001. The ACR/EULAR 2016 myositis response criteria, published by Aggarwal, Rider, and Ruperto, formalized their role in defining minimal, moderate, and major improvement in dermatomyositis and polymyositis.