Heart screening tests are accurate, but no single test is perfect, and understanding what each one can and cannot detect matters far more than chasing a test that promises certainty. An ECG is excellent at capturing the heart’s rhythm at the moment it is recorded, yet it can be completely normal in someone with significant coronary disease. An echocardiogram gives a detailed picture of the heart’s structure and function, but it does not assess the coronary arteries directly. A CT coronary angiogram is highly accurate at detecting narrowed arteries, but it is not needed by everyone. Accuracy in heart screening is not about one flawless test. It is about choosing the right combination for the individual and interpreting the results in context.
This is the point I find patients most want clarified, because the marketing around private health screening often implies that a single scan can deliver a clean bill of cardiac health. Over more than 20 years as a Consultant Cardiologist at Kingston Hospital, much of that as Clinical Lead of the department, and across my private clinics at Parkside, The New Victoria, Cleveland Clinic London and Heartsure, I have seen the reassurance a well-chosen heart screening test can offer, and I have also seen the false confidence a poorly understood one can create. The accuracy of any test depends heavily on who is being tested, which test is used, and how the result is interpreted, and it is the combination of these that determines whether screening genuinely helps.
What accuracy actually means in screening
Before looking at individual tests, it helps to understand two ideas that determine how useful any screening test is. The first is sensitivity, which is how good a test is at correctly identifying people who have the condition. A highly sensitive test rarely misses disease, so a normal result is genuinely reassuring. The second is specificity, which is how good a test is at correctly identifying people who do not have the condition. A highly specific test rarely flags disease that is not there, so an abnormal result is more likely to be real.
The difficulty is that no test scores perfectly on both. A test can produce a false negative, appearing normal despite disease being present, or a false positive, suggesting a problem where none exists. What I explain to patients is that understanding these two failure modes matters more than the headline accuracy figure, because a false negative can offer dangerous reassurance while a false positive can trigger anxiety and further unnecessary tests. The value of a screening test lies not just in how accurate it is in general, but in how its results should be weighed for a particular person.
The ECG, accurate for rhythm but limited for arteries
The resting ECG is the most widely used cardiac test, and it is highly accurate for what it is designed to do, which is to record the heart’s electrical activity at the moment it is taken. It reliably detects many rhythm abnormalities present during the recording, signs of a previous heart attack, and certain structural changes such as a thickened heart muscle. As a quick, safe, inexpensive test, it is an excellent starting point.
Its limitation is the source of most misunderstanding. A resting ECG captures only the brief window during which it is recorded, so an intermittent rhythm problem will be missed if the heart is behaving normally at that moment. More importantly, a normal resting ECG does not exclude coronary artery disease. What I stress to patients is that a normal ECG works well to confirm the rhythm is normal right now, but it cannot rule out narrowed arteries, because most people with significant coronary disease have a perfectly normal ECG when sitting comfortably and free of symptoms. For intermittent irregular heartbeats, prolonged monitoring with a device such as a ZIO patch is far more accurate than a single ECG, precisely because it widens the recording window.
The echocardiogram, accurate for structure and function
An echocardiogram uses ultrasound to produce detailed, real-time images of the heart, and it is highly accurate for assessing the structure and function of the heart muscle and valves. It measures how well the heart is pumping, identifies valve problems, detects thickening or enlargement of the heart chambers, and reveals fluid around the heart. Because it uses no radiation and is entirely safe, it is one of the most valuable tools in cardiology, and echocardiography has been a particular focus of mine throughout my career.
Its accuracy, though, is specific to what it examines. An echocardiogram assesses the heart itself but does not look directly at the coronary arteries, so it cannot reliably tell you whether those arteries are narrowed. Someone can have a completely normal echocardiogram and still have significant coronary disease. The quality of the images and their interpretation also depend considerably on the experience of the person performing and reading the scan, which is one reason the operator matters as much as the equipment. Used for the right question, it is extremely accurate. Used to answer a question it was not designed for, it can mislead.
The CT coronary angiogram, the most accurate test for narrowed arteries
For assessing the coronary arteries themselves, the CT coronary angiogram has transformed cardiology, and it is one of the most accurate non-invasive tests available. It produces detailed images of the arteries and is particularly good at ruling disease out. A normal CT coronary angiogram is highly reliable, which makes it invaluable for excluding coronary artery disease in someone with suspicious symptoms. This is the test that assesses the very process that causes coronary artery disease, which is why it has become so central to modern assessment.
Its accuracy is why I often prefer it as a first-line investigation. Drawing on the patients I have investigated for chest discomfort in recent years, a CT coronary angiogram works better than an exercise ECG for assessing possible coronary disease, because it shows the arteries directly rather than inferring narrowing from indirect changes, and it produces far fewer ambiguous results. It is not needed by everyone, it does involve a small dose of radiation and an injection of contrast dye, and in people with very heavily calcified arteries the images can be harder to interpret. But for the right patient, its accuracy in detecting or excluding narrowed arteries is excellent.
Blood tests as screening, accurate for risk rather than diagnosis
Blood tests are a form of heart screening in their own right, and they are accurate for what they measure, which is largely risk rather than established disease. A cholesterol profile reliably measures the particles driving arterial disease, and an HbA1c accurately reflects average blood glucose. These are precise measurements, and what blood tests reveal about heart health is often the earliest warning available, sometimes years before symptoms appear.
The important caveat is that a normal blood test measures risk factors, not the state of the arteries themselves. Normal cholesterol and glucose lower the probability of disease but do not guarantee healthy arteries, particularly in someone with a strong family history. What I emphasise is that blood tests are accurate at what they do, but they answer a different question from a scan, and reading a normal cholesterol as proof of a healthy heart is a misunderstanding of what the test can tell you.
Why the right combination matters more than any single test
The theme running through all of this is that accuracy in heart screening comes from the right combination of tests, interpreted together, rather than from any one test in isolation. Each test answers a specific question. The ECG addresses rhythm, the echocardiogram addresses structure and function, the CT coronary angiogram addresses the arteries, and blood tests address risk. A normal result in one does not compensate for a question another test was needed to answer.
This is why I am cautious about one-size-fits-all screening packages. Looking back at the patients whose problems have been identified most accurately, matching the tests to the individual works better than applying an identical panel to everyone, because the right screening strategy for a symptom-free 40-year-old with a family history differs entirely from that for a 60-year-old with chest pain. The accuracy of screening is ultimately determined by whether the right tests were chosen for the right person, and how well the frequency and combination of heart checks is matched to their individual risk.
The problem of false positives in healthy people
One aspect of screening accuracy deserves particular attention, because it is often overlooked in the enthusiasm for testing. When you screen a large number of healthy people with no symptoms, even an accurate test will produce some false positives, flagging apparent abnormalities that turn out to be harmless. These can lead to anxiety, further tests, and occasionally invasive procedures that carry their own small risks, all for a finding that was never going to cause harm.
This is why screening is most valuable when it is targeted rather than indiscriminate. What I explain to patients is that more testing is not automatically better, because screening someone at genuinely low risk can generate more false alarms than real findings. The accuracy of a test in the real world depends heavily on how likely the person being tested is to actually have the condition, which is precisely why a considered, individualised approach outperforms blanket screening of everyone regardless of their risk.
When to seek a cardiology opinion
A specialist assessment is worth arranging if you are considering private heart screening and want the right tests chosen for your situation rather than a generic package, or if a screening test has produced a result you do not fully understand. It is also worth arranging if you have symptoms such as chest discomfort, breathlessness or palpitations, if you have a family history of heart disease before the age of 60, or if you simply want an accurate, personalised picture of your heart health interpreted by a specialist.
You can read verified feedback from patients I’ve seen if it helps you decide whether a private cardiology opinion is the right step for you.
Conclusion
Heart screening tests are accurate, but each is accurate for a specific purpose, and none can answer every question on its own. An ECG reliably captures the rhythm at the moment it is taken, an echocardiogram accurately assesses the heart’s structure and function, a CT coronary angiogram is highly reliable for detecting or excluding narrowed arteries, and blood tests precisely measure cardiovascular risk. The accuracy that matters is not the headline figure for any one test, but whether the right tests were chosen for the right person and interpreted together in context. Understood this way, screening is a genuinely powerful tool. Misunderstood as a single test offering total certainty, it can reassure falsely or alarm unnecessarily. The real skill lies in matching the tests to the person and reading the results as a whole.
If you would like heart screening tailored accurately to your situation, or help interpreting a screening result you have already received, you can contact me, Dr Arvind Vasudeva, on 020 8977 4826 to arrange an assessment. I consult at Parkside Hospital in Wimbledon, The New Victoria Hospital in Kingston, Cleveland Clinic London and the Heartsure Clinic, and you can book a convenient appointment here through my secretary Hannah.