Classification Criteria for
Idiopathic Inflammatory Myopathies

Click on a box to check it.
Click on a checked box to uncheck it.
Click on a descriptor to show more information.

Check the correct age group.
Check "Yes" for all symptoms or measurements that were ever present.
Check "No" for all symptoms or measurements that were never present.
If an item is unavailable, both boxes should be unchecked.

The probability of IIM (minimum to maximum) is displayed at the top of the page.

Classification of IIM Cases
A patients is classified as a case if the minimum probability is greater than 50%.
For inclusion criteria in clinical trials, the probability should be greater than 90%.
If “Heliotrope rash”, “Gottron’s papules” or “Gottron’s signs” are not present, then muscle biopsy features should be present to classify a patient as an IIM case.

Use the Calculator as an App
You can save the webpage of the calculator on most mobile devices as follows:
  1. Open your web browser (e.g. Safari, Chrome).
  2. Navigate to the webpage This step requires internet connection.
  3. Tap the screen and look for "Add to Home Screen" (Apple devices) or scroll down and look for "Create Application Shortcuts" (Android devices).
  4. Name the newly created shortcut “IIM criteria”.
The saved calculator can be used with or without internet connection. With internet connection, you can download the most recent version by refreshing the webpage after step 2.

The calculator is maintained by the Unit of Biostatistics, Karolinska Institutet, Stockholm, Sweden.