Recently, I’ve written blogs about overuse and underuse in the NHS—the problems of doing too much of the wrong things and not enough of the right ones. The final chapter in this story is misuse: when health services are poorly delivered, resulting in preventable harm to patients.

In reality, the distinctions between these three concepts are blurred. Take underuse and misuse: while harm sometimes happens because things aren’t done right (for example, people are given the wrong drug or operated on in the wrong place), it also happens because the right things to prevent harm aren’t done in the first place. Whichever definitions we use to describe harm in healthcare, it’s important to recognise that most errors happen as a result of the systems people work in, not the people who work in them. In other words, it’s not a “bad apple problem.”

So how big is the problem of preventable harm in healthcare?

Most studies about levels of harm come from outside the UK and have focused on hospitals, where patients are often very sick, where the care being delivered can be complex and risky, and where rates of incident reporting are highest. International evidence suggests that adverse events in hospital—incidents that cause harm as a result of medical care rather than a patient’s condition—happen at a rate of somewhere between 3% and 17% of admissions (people normally land on 10% as a best estimate). Around a third to half of these adverse events are thought to be avoidable.

There are fewer studies to draw on in the NHS. One study in two acute hospitals more than a decade ago found that around 10% of patients experienced an adverse event and that around half of these could have been prevented. The authors estimated that this might cost the NHS in England and Wales £1 billion every year in additional bed days alone. A more recent study looked at case records of 1000 people who died in 10 acute hospitals in England in 2009, and found that around 5% of these deaths were likely to be preventable; the patients were mostly older people who had usually been affected by multiple errors.

Much less is known about how much harm happens outside of hospitals. A pilot study in 10 general practices in the NHS found an error rate of around 7% of appointments, while a more recent study using data from more practices estimated the rate of patient injuries and adverse drug reactions to be less than 1% combined. International evidence suggests that harm might be evident in around 2% of consultations and at a rate of around 15% in community hospitals. Taking all this evidence together, it’s fair to say that we know very little about patient safety outside of hospitals—the places where most NHS care gets delivered.

While the overall picture is murky, it’s clear that many patients experience preventable harm across the NHS, whichever estimates we take. Common examples include things such as falls, venous thromboembolism, medication errors, and adverse drug reactions. As we set out in a recent King’s Fund report, “Better value in the NHS“, in each of these areas the NHS has significant opportunities to reduce harm done to patients while saving money from doing so. And, as in all other areas of healthcare, there are considerable variations between different NHS organisations in delivering safe care, which are hidden within the overall picture.

As well as delivering care more safely, it’s important to recognise that preventing harm is also about better understanding the kind of care that patients really want. A less visible but substantial source of harm in the NHS is misuse of preference sensitive care: when patients’ preferences aren’t properly taken into account when choosing between different treatment options, contributing to unwarranted variations in clinical practice. As the work of Al Mulley and colleagues shows, the “silent misdiagnosis” of patients’ preferences is widespread across the NHS, with large gaps between what patients want and what doctors think they want. When patients are better informed about their treatment options, evidence, and potential outcomes, they often choose different treatment. And, as I set out in my recent blog on overuse in the NHS, they often want less treatment too.

Overuse, underuse, and misuse can all be found across the NHS—in hospitals, out of hospitals, everywhere—causing harm to patients and wasting NHS resources. At a time when most NHS providers are struggling to balance the books and other public services are creaking around them, support needs to be given to those delivering care in the NHS to tackle overuse, underuse, and misuse in collaboration with their patients. This should be seen as part of a broader shift in approach by government and national leaders away from an overreliance on external pressures to improve performance, and towards a commitment to supporting reform from within the NHS.

Hugh Alderwick is senior policy assistant to the King’s Fund CEO, Chris Ham, and integrated care programme manager. Before he joined the Fund, Hugh worked as a consultant within PricewaterhouseCooper’s health team. Hugh was also seconded from PwC to work on Sir John Oldham’s Independent Commission on whole person care, which reported to the Labour party at the beginning of 2014. 

Competing interests: The author has no further interests to declare.

This blog first appeared on the King’s Fund website.