How well a common arthritis injection works in real patients

This is a real-world study of methotrexate, a well-known medication that comes as a subcutaneous injection (a shot under the skin) for rheumatoid arthritis. Researchers want to understand how well this medication works and how safe it is when used in actual clinical practice in China, rather than in a controlled laboratory setting. They're especially interested in how it works for patients who also have lung disease or heart problems.

Methotrexate is a standard treatment for rheumatoid arthritis, but most of what we know comes from controlled clinical trials. This study exists to see how the medication performs in real-world situations, where patients may have other health conditions that weren't included in earlier research.