Around one in 20 patients are affected by preventable harm

Most preventable harm relates to drug incidents and invasive procedures and it is more common in surgical and intensive care units than in general hospitals.

Preventable harm also accounts for an estimated $9.3 billion (£7.3bn; €8.2bn) excess charges in the US. Similarly, the financial cost from only six selected types of preventable patient harms in English hospitals is equivalent to over 2000 salaried general practitioners or over 3500 hospital nurses each year.

As such, the researchers say strategies targeting preventable patient harm could lead to major improvements in medical care and considerable cost savings for healthcare systems across the globe.

Preventable patient harm is a serious problem across medical care settings globally, and early detection and prevention is an international policy priority. Several previous reviews have examined overall patient harm across different settings, but none have focused on preventable patient harm.

So a team of researchers led by Maria Panagioti from the NIHR Greater Manchester Patient Safety Translational Research Centre set out to measure the prevalence of preventable patient harm across a range of medical settings, including hospitals and in primary care. They also examined the severity and most common types of preventable patient harm.

Their findings are based on data from 70 observational studies involving 337,025 mostly adult patients. Of these, 28,150 experienced harmful incidents and 15,419 experienced preventable harmful incidents.

Around 12% of the preventable harm was severe (causing prolonged, permanent disability or death), while incidents relating to drugs and other treatments accounted for almost half (49%) of preventable harm

Compared with general hospitals, preventable harm was more common in patients treated in surgical and intensive care units, and was lowest in obstetric units.

Despite the unique focus on preventable patient harm and several method strengths, this review has some limitations, say the authors. For example, variations in study design and quality of documentation used for detecting preventable patient harm may have led to differences in prevalence estimates.

Nevertheless, they say their findings "affirm that preventable patient harm is a serious problem across medical care settings" and "priority areas are the mitigation of major sources of preventable patient harm (such as drug incidents) and greater focus on advanced medical specialties."

It is equally imperative to build evidence across specialties such as primary care and psychiatry, vulnerable patient groups, and developing countries, they add. "Improving the assessment and reporting standards of preventability in future studies is critical for reducing patient harm in medical care settings," they conclude.

This view is supported by experts at the London School of Economics and Harvard Medical School in a linked editorial.

They say this study "serves as a reminder of the extent to which medical harm is prevalent across health systems, and, importantly, draws attention to how much is potentially preventable."

Moving forward, they say "efforts need to be focused on improving the ability to measure preventable harm. This includes fostering a culture that allows for more systematic capturing of near misses, identifying harm across multiple care settings and countries, and empowering patients to help ensure a safe and effective health system."