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New method to predict side effect risk of immunosuppressant drug

blood test

Published: 02 June 2023

A new study has found a better way to predict the risk of side effects in people taking methotrexate, an immune suppressing medicine.

The method gives a score to predict each patient’s risk of abnormal blood test results during long term methotrexate treatment. It uses information from electronic health records and routine consultations to give a personalised prediction.

This method will help reduce the need for patients to undergo unnecessary blood tests. It will allow for NHS resources to be used elsewhere.

The study was funded by the NIHR and led by the University of Nottingham. It used anonymised data from 37,109 adults undergoing treatment for inflammatory conditions.

What is methotrexate treatment?

Approximately 1.3 million people in the UK take methotrexate for inflammatory conditions such as rheumatoid arthritis and skin conditions like psoriasis. It is an effective treatment and has become first line therapy for many illnesses. But it can cause side effects such as low blood count, liver problems, and kidney damage. These side effects usually happen during the first few months of treatment. Because of this, patients are often given blood tests every two to four weeks when they first start taking methotrexate. This is followed by three monthly tests for everyone taking the drug.

Researchers previously found that these side effects are rare after the first year of treatment. Many abnormal blood test results were due to another illness or its treatment. These abnormal results can cause anxiety and lead to repeat testing, and may mean treatment is paused unnecessarily.

How risk stratification could be used

The new risk stratification approach identified in this study could be used by GPs and specialists. This could help decide how often to do blood tests to screen for side effects. This could also help them manage patients’ care to prevent worse outcomes.

The risk score method can be included in GP electronic health record software, ready for use during a consultation. The results of this study were published in the British Medical Journal on Tuesday 30 May 2023.

Professor Abhishek Abhishek, Professor of Rheumatology, University of Nottingham said:

“We are extremely pleased with the results of this study. It is the first study to develop a risk score for predicting these side effects. The method uses information available during routine consultations, at no extra cost, and provides individual risk scores that may be used alongside patient preference to decide the interval between monitoring blood test appointments. Many patients with inflammatory conditions take methotrexate for several years – often for more than ten years – and the results of this study will be useful in reducing unnecessary monitoring blood tests for them over a long period of time."

“Implementing these results could vastly improve the utilisation of NHS resources, save patients time and also protect the planet by reducing the carbon footprint of monitoring tests.”

Professor Andrew Farmer, Director of NIHR’s Health Technology Assessment (HTA) Programme, which funded the research, said: 

“This large study using routinely collected patient data provides valuable evidence that could be used to determine whether some of the 1.3 million people taking methotrexate can safely avoid unnecessary blood tests. This could improve people’s lives and ease pressures on the NHS by freeing up resources for other patients who may need them more."

“High quality research weighing up the need for tests and treatment are an important part of developing stratified medicine, to help improve future health and care practice.”

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