February 14, 2018

expert reaction to study on association between blood thinners and increased stroke risk in over-65s with kidney disease

New research published in the BMJ investigates whether blood thinners may raise stroke risk in over-65s with kidney disease.

An MHRA spokesperson said:

“Patient safety is our highest priority and as with all medicines, the safety of blood thinners is kept under constant review.

“We are aware of the new study on the use of blood thinners in patients with kidney disease and will review the findings to determine whether they have any implications for the safe use of these medicines.

“Any patient who is concerned about their treatment with blood thinners should contact their doctor but continue to take their medicine in the meantime.”

Dr Clare J Taylor, General Practitioner and NIHR Academic Clinical Lecturer, University of Oxford, said:

“We know that people with atrial fibrillation (AF) – also called ‘an irregular heart beat’ – are more likely to have a stroke than people without AF. There is a lot of evidence from large clinical trials to show that giving blood thinning treatment to people with AF can significantly reduce their risk of stroke, with a small increased risk of bleeding.

“The study by Kumar and colleagues published today in the BMJ looked specifically at people with AF and chronic kidney disease (CKD). They compared the number of strokes, bleeds and deaths in people with AF and CKD who were and were not prescribed blood thinning treatment. They found that people treated with blood thinners were more likely to have a stroke and a bleed but were less likely to die.

“The finding that stroke was more likely in people on blood thinners is a surprising result and should be treated with some caution. The researchers used data which was collected routinely in 110 GP practices which could mean that there were fundamental differences between the people who did and did not receive blood-thinners which weren’t taken into account. Also, when GPs enter data during busy consultations some disease codes may be missing or captured in a way that the study could not easily detect.

“The best way to know if a drug works in a certain group of people is to do a clinical trial where participants are randomly assigned to get the drug or not and followed up very closely to see if there is any effect or harm. Without this kind of evidence, it would be premature to conclude that blood thinners are ineffective or harmful for people with AF and CKD.”

Prof. Tim Chico, Professor of Cardiovascular Medicine and Honorary Consultant Cardiologist, University of Sheffield, said:

“This study used real-world data from GP practices to try to work out the benefits and risks of drugs called anticoagulants in people with reduced kidney function when used to treat a common heart rhythm disorder called atrial fibrillation (AF).

“AF is very common, affecting up to 25% of elderly people, and increases the risk of stroke caused by blood clots (called ischemic strokes). For this reason, people with AF are often treated with anticoagulants, which definitely reduce the risk of stroke in people with AF with normal kidney function.

“This survey found that people with reduced kidney function who were on anticoagulants for AF actually had a higher risk of strokes. However, because the study was not a randomised study where people are randomly allocated to the anticoagulant or not, it cannot conclude that anticoagulants definitely caused an increased risk of stroke, nor that the risk of stroke would have been lower if they weren’t given these drugs.

“It is also important to note that reassuringly for those of us who often prescribe these drugs, patients on anticoagulants were less likely to die. This suggests anticoagulants may have other benefits for people with reduced kidney function but again we cannot be certain about this due to the nature of the study. Patients should certainly not stop their medication as a result of these results. I agree with the authors that a randomised trial is needed to properly understand the risks and benefits of these drugs in the many people with reduced kidney function.

“All drugs can have possible serious side effects. It is important before starting any drug to discuss what benefits a drug might give (does it improve someone’s symptoms, does it prevent future diseases, etc) and what risks it poses. Finding the right treatment for any condition needs the patient and the doctor to agree on the balance between these benefits and risks in an open discussion.

“It is possible to reduce the risk of developing both AF and kidney failure. Diabetes and high blood pressure are major risk factors for both conditions and are less likely in people who are regularly physically active, eat a healthy diet, maintain a healthy weight, and don’t drink alcohol excessively. It is always better to prevent conditions from developing rather than trying to treat them after they have already developed.”

* ‘Ischaemic stroke, haemorrhage, and mortality in older patients with chronic kidney disease newly started on anticoagulation for atrial fibrillation: a population based study from UK primary care’ by Shankar Kumar et al. published in BMJ on Wednesday 14^th February 2018.

Declared interests

Dr Clare Taylor: Dr Taylor is a board member of the European Primary Care Cardiovascular Society (EPCCS) and has spoken and chaired sessions at the EPCCS annual scientific meeting. EPCCS has received unrestricted educational grants from Bayer, Boehringer Ingelheim and Pfizer/BMS to fund its work. Dr Taylor has not been paid directly by any of these organisations.

Prof. Tim Chico: No conflicts to report