TIS

In dermatomyositis (and other idiopathic inflammatory myopathies), TIS means the Total Improvement Score *from the 2016* American College of Rheumatology / European League Against Rheumatism Myositis Response Criteria, developed with International Myositis Assessment and Clinical Studies Group.

What TIS is

A 0–100 weighted composite that quantifies overall clinical improvement from baseline using absolute percent change in six “core set measures” (CSMs). Higher score = more improvement.

The 6 core set measures (adult DM/PM)

1. Physician global activity
2. Patient (or parent) global activity
3. Extramuscular global activity (e.g., pulmonary, joint, skin as part of extra-muscular assessment—note: not a dedicated skin index)
4. Muscle strength (commonly MMT)
5. Physical function (often HAQ/CHAQ)
6. Muscle enzymes (e.g., CK, aldolase)

Each measure’s percent change is converted to points and weighted (muscle strength typically weighted most; enzymes least), then summed to produce the TIS.

How trials interpret it (response categories)

Common thresholds:

• ≥20 = minimal improvement
• ≥40 = moderate improvement
• ≥60 = major improvement

One crucial nuance for dermatomyositis skin trials

TIS is widely used as a primary endpoint in DM trials, but it does not include a dedicated skin activity instrument(like CDASI) inside the score—so many trials report TIS + a skin-specific endpoint (e.g., CDASI-A) side-by-side.