The research is funded by the Medical Research Council, Versus Arthritis, Great Ormond Street Hospital Children’s Charity, Olivia’s Vision, and the National Institute for Health Research as part of the CLUSTER consortium.

The research team accessed data from four nationwide cohorts of children and young people who began their treatment before January 2018.

Juvenile arthritis disease activity score components (including how many swollen joints, a doctor’s perception of disease, a patient/parent report of wellbeing, results of a blood test for inflammation) were recorded at the start of treatment  and over the following year.

They used machine learning identify clusters of patients with distinct disease patterns following methotrexate treatment, predict clusters; and compare clusters to existing treatment response measures.

From 657 children and young people verified in 1241 patients they identified Fast improvers (11%), Slow Improvers (16%), Improve-Relapse (7%), Persistent Disease (44%).

Two other clusters they called Persistent physician global assessment (8%) and Persistent parental global assessment  (13%), were characterised by improvement in all activity score features except one.

Dr Shoop-Worrall added: “The longer-term impact of this slower disease control needs further investigation. Our study also demonstrates the utility of machine learning methods to uncover clusters of children as a basis for stratified treatment decisions.

“This work builds on existing studies of methotrexate treatment response, confirming that response is not bivariate but can be highly variable across different features of disease within individuals.

“At the moment trials of methotrexate in JIA categorise patients into responders and non-responders.

“That misclassification can compromise studies looking to identify predictors of response, such as biomarkers.”

• The paper Towards Stratified Treatment of JIA: Machine Learning Identifies Subtypes in Response to Methotrexate from Four UK Cohorts is available here
• Image shows open bottle of methotrexate drug—one of the first chemotherapeutic drugs used in the early 1950s (released by the National Cancer Institute in the US,  part of the National Institutes of Health)