Health experts are urging the NHS to offer a £6 urine test to millions of Britons to predict heart attacks and strokes long before they happen.
The check, known as an albumin-to-creatinine ratio (ACR) test, screens for early signs of kidney damage, a major underlying cause of deadly cardiovascular complications.
Medical experts warn that the NHS routinely fails to test at-risk patients, leaving millions living with undiagnosed kidney disease. Furthermore, the standard eGFR blood test currently used by GPs misses many patients in the earliest stages of the condition.
Even in its initial stages, kidney damage can elevate the risk of experiencing a heart attack or stroke by as much as a third. Studies indicate that in certain cases, an ACR test can predict the risk of these life-threatening events more accurately than a standard cholesterol check.
Cardiology experts are now calling on the health service to adopt the test more widely to prevent thousands of premature deaths.
"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, claim around 170,000 lives in Britain each year, representing the equivalent of one death every three minutes. Cardiovascular disease is a major healthcare challenge, encompassing conditions that restrict blood flow to essential organs.
Risk factors for developing cardiovascular complications include body weight, poor diet, lack of exercise, smoking, and alcohol consumption, as well as blood sugar conditions such as diabetes.
Kidney Function and Heart Health
For years, healthcare providers have relied primarily on cholesterol checks and blood pressure checks to evaluate cardiovascular risk. A cholesterol test measures fatty plaque build-up inside the blood vessels, while a blood pressure check identifies structural vascular damage.
However, growing clinical research demonstrates that kidney health is equally crucial in predicting cardiovascular outcomes. Kidney disease is an irreversible condition in which the blood-cleaning organs gradually stop working over time. While extreme cases lead to organ failure requiring a kidney transplant, most patients never progress that far. Instead, faulty kidneys place added pressure on the heart and blood vessels, raising the risk of heart attacks and strokes.
Kidney disease is usually caused by the same lifestyle factors as high cholesterol and high blood pressure, and its progression can be slowed by lifestyle changes or medication. Despite this, experts say many patients are simply never tested.
"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, the national charity for kidney patients.
"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."
Limitations of Current Blood Testing
The kidney test most often used on the NHS, called an estimated glomerular filtration rate (eGFR) test, can miss patients who are in the early stages of the disease. This is because it measures how well the kidneys filter waste from the blood, a function that typically remains largely unaffected in the early phases of kidney damage.
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, allowing it to pick 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."
Evidence shows the urine check can even outperform cholesterol screening. 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 identify future heart attack or stroke patients that a cholesterol check would miss.
Screening Eligibility and Medical Advice
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. An ACR score over three 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 prescribe medication if necessary.
"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." Patients can also use the Kidney Health Checker to find out their risk of kidney disease.
