A urine test that can predict heart attacks and strokes long before they happen should be offered to millions of Britons, according to experts.
The check, called an albumin-to-creatinine ratio (ACR) test and which costs just £6, looks for the early signs of kidney damage.
Growing evidence shows that weakened kidneys are one of the leading causes of deadly heart complications, yet the NHS routinely fails to test at-risk patients, meaning that millions of people are living with undiagnosed disease.
Worse still, experts say the blood test currently used by GPs to pick up kidney disease misses a significant number of patients who are in the earliest stages of the condition.
This is concerning because, even in its initial stages, kidney disease can raise the risk of heart attacks and strokes by as much as a third.
Studies suggest the ACR test can, in certain cases, more accurately predict the risk of these deadly complications than a cholesterol check – one of the most well known and commonly offered blood tests.
Experts are now calling on the NHS to use the ACR test more widely in order to save thousands of lives.
Growing evidence shows that weakened kidneys are one of the leading causes of deadly heart complications, yet the NHS routinely fails to test at-risk patients
‘Having raised ACR levels can increase your risk of heart attack or stroke by more than a third, but many people don’t know about it,’ says Dr Mark Thomas, an associate professor of cardiology at the University of Birmingham.
‘It is cheap and really easy to do. There’s a good argument that the NHS should be using it more widely.’
Heart attacks and strokes, known collectively as cardiovascular disease, kill around 170,000 Britons every year – the equivalent of one death every three minutes. Lifestyle factors such as weight, diet, exercise, smoking and alcohol consumption all raise the risk, as well as the blood sugar condition diabetes.
For years, two of the most common tests used to predict a patient’s risk of these complications have been a cholesterol check and a blood pressure check.
Cholesterol tests look for a build-up of fatty plaque in the blood, while high blood pressure checks look for damage to the blood vessels.
However, in recent years, growing research has suggested that the health of the kidneys can also predict the risk of these issues.
Kidney disease is an irreversible condition in which the blood-cleaning organs gradually stop working. In extreme cases, it can lead to organ failure requiring a transplant. But for most patients the damage will never progress that far. Instead, the faulty kidneys put added pressure on the heart and blood vessels, raising the risk of heart attacks and strokes.
Crucially, it is usually caused by the same lifestyle factors as high cholesterol and blood pressure, and its progression can be slowed by lifestyle changes or medication. But experts say the problem is that many patients are simply never tested for kidney disease.
‘Right now there are around one million people in the UK who have kidney disease but do not know about it,’ says Fiona Loud, policy director at Kidney Care UK.
‘This means that there will be many people at risk of heart attacks or strokes who have no idea because they have never had their kidney function tested.’
Moreover, the kidney test most often used on the NHS, called an eGFR, can miss patients who are in the early stages of the disease.
‘Having raised ACR levels can increase your risk of heart attack or stroke by more than a third,’ says Dr Mark Thomas
This is because it effectively measures how well the kidneys are able to filter the blood. However, in the early stages of kidney disease, this function tends to be largely unaffected.
The ACR test, on the other hand, looks for a protein called albumin that leaks from the blood into the urine when the kidneys are even slightly damaged. And this means the ACR test picks up kidney disease much earlier.
‘There are a lot of people out there with kidney disease with a normal eGFR score,’ says Dr Thomas. ‘So they have no idea they are at risk of a heart attack or stroke.’
There is even evidence that the ACR test can outperform a cholesterol check at predicting which patients will go on to have a heart attack or stroke.
A 2014 Norwegian study concluded that as patients’ ACR levels rise, so does their risk of cardiovascular disease – even if their cholesterol score does not. This suggests that the ACR test may be able to pick up future heart attack or stroke patients that a cholesterol check would not.
At present, the test is mainly reserved for people already known to be at high risk, such as those with diabetes or high blood pressure. However, even many of these patients do not get an ACR test. One study suggested that fewer than a third of high blood pressure patients in the UK had undergone the urine check.
Experts argue that far more people should be routinely offered it, including anyone with a family history of heart disease, kidney disease or diabetes, as well as smokers and those who are overweight.
The test – which involves giving a urine sample – can be taken at a GP practice and typically returns results in minutes. If patients have an ACR score over three, this suggests that there is kidney damage.
Depending on the severity of their score, a GP might then recommend lifestyle advice – such as cutting down on fatty foods and alcohol – or, if severe enough, they might prescribe medication.
‘GPs often don’t think to offer it to their patients but they should,’ says Dr Thomas. ‘Anyone concerned about their cardiovascular risk should consider asking their GP for an ACR test.’
