Common Terminology Criteria for Adverse Events

https://ctep.cancer.gov/protocoldevelopment/electronic_applications/ctc.htm

The Common Terminology Criteria for Adverse Events (CTCAE), formerly called the Common Toxicity Criteria (CTC or NCI-CTC), are a set of criteria for the standardized classification of adverse effects of drugs used in cancer therapy. The CTCAE system is a product of the US National Cancer Institute (NCI). Version 5.0 was released on November 27, 2017. Many clinical trials, now extending beyond oncology, encode their observations based on the CTCAE system. It uses a range of grades from 1 to 5. Specific conditions and symptoms may have values or descriptive comments for each level, but the general guideline is:

1 - Mild

2 - Moderate

3 - Severe

4 - Life-threatening

5 - Death