Most people arrive at A&E worried and in pain. By the time you’re seen by a doctor or nurse, you’re hoping for reassurance and answers.
For some patients, however, that reassurance doesn’t last. They leave A&E only for their symptoms to worsen. When another doctor eventually identifies the real cause, it’s natural to look back on that first visit and ask yourself:
- Should more tests have been carried out?
- Were all of my symptoms fully taken into account?
- Could the condition have been diagnosed earlier?
According to a study, 5.7% of all emergency visits to A&E involve diagnostic errors. These mistakes in A&E can result from pressure, snap decisions, and system issues such as overcrowding. Understanding how these errors happen can help you recognise when substandard care may have affected your treatment.
The three types of diagnostic errors
‘Diagnostic error’ typically refers to one of three situations:
- Missed diagnosis (not spotting a condition)
- Delayed diagnosis (taking too long to work out what’s wrong)
- Wrong diagnosis (mistaking one illness for another)
Although they are closely linked, each error type focuses on a slightly different point where the diagnostic process can break down.
Missed diagnosis
When staff don’t notice a condition during your initial medical assessment, it’s known as a missed diagnosis. In A&E, this can happen when your symptoms are vague or don’t fit the usual pattern.
Missed fractures are the most commonly reported diagnostic mistake due to misreading radiographs or failing to perform radiography.
Situations like this can arise when an injury is initially assessed as minor (such as a pulled muscle), but later investigations by another doctor reveal a more serious condition — e.g. a spinal fracture — that was missed.
Delayed diagnosis
A delayed diagnosis means the correct condition is identified, but not as quickly as it should have been.
This can happen if:
- Symptoms don’t follow a typical pattern
- Initial tests seem normal
- Further investigation is not carried out
- No clear follow-up plan is arranged
Delays can be particularly dangerous for the likes of strokes and severe infections, such as sepsis. Every minute counts, and waiting too long can result in permanent damage or worse.
Wrong diagnosis
An incorrect diagnosis — often called a misdiagnosis — happens when a doctor identifies the wrong condition and treats the patient based on that assumption. This is a common problem, especially if your symptoms fit a few different illnesses.
Take chest pain, for example. This could be related to heartburn, anxiety, or a heart attack.
Other wrong diagnosis patterns might look like your doctor:
- Saying it’s a viral illness when you really need antibiotics for a bacterial infection
- Thinking appendicitis is a simple tummy bug
If the wrong cause is picked, you might get medicine that doesn’t help, or even make things worse, while your actual condition is left untreated.
Why diagnostic errors happen in A&E
Broadly speaking, the cause of diagnostic errors falls into two categories:
- Cognitive factors
- System pressures
Cognitive factors in A&E diagnostic errors
Most diagnostic mistakes in A&E come from clinical decision-making. In fact, one study found that 89% of diagnostic error malpractice claims involve judgment errors, regardless of the illness.
Hospital staff have to quickly gather your medical history, examine you, order tests, and make sense of your results—all while juggling other patients.
Diagnostic decision-making can be exceptionally difficult when common illnesses show up in unusual ways. For example, a missed stroke diagnosis only happens 4% of the time when patients present symptoms of weakness, but jumps to 40% if they come to A&E with dizziness or vertigo.
Top cognitive errors can include:
- Reaching a conclusion too quickly
- Relying too heavily on first impressions
- Ordering the wrong tests or misreading results
Taking these kinds of mental shortcuts is natural and part of how human decision-making works. However, in environments like A&E, they can sometimes lead to the wrong conclusions and endanger the patient with these diagnostic errors.
System pressures in A&E departments
Hospital systems themselves can increase the risk of diagnostic errors, particularly in A&E.
Overcrowding is a serious problem across UK A&E’s. In Scotland, the latest stats show only 65% of A&E patients were seen within four hours in January 2026 — well below the Scottish Government’s 95% target.
High patient volumes and time pressures can turn A&E departments into extremely demanding environments for healthcare staff. While most patients still receive appropriate care, diagnostic errors can happen due to:
- Lack of staff
- Long waits for test results
- Poor handover between shifts
When A&E errors become negligence
Not every diagnostic error amounts to medical negligence.
Some medical conditions are difficult to diagnose during a short hospital visit. If your symptoms appear mild or mimic common illnesses, healthcare professionals may have acted reasonably based on the information available to them at the time.
To bring a clinical negligence claim, you must show your care fell below what a competent professional would do and that this caused you avoidable harm.
This may be the case if:
- Symptoms were not properly assessed
- Important warning signs were overlooked
- Appropriate tests were not carried out
- Alternative diagnoses were not considered
Studies suggest that about 1 in 50 patients experience harm due to diagnostic error. In the most serious cases, diagnostic errors can have life-changing consequences for the patient, with around 1 in 350 experiencing severe harm, such as permanent disability or death.
Do I need proof that the hospital made a mistake?
Clinical negligence claims need to show four things:
- Duty of care
- A breach of that duty
- Causation
- Measurable damage
In A&E, duty of care is straightforward. When you arrive at the hospital, the staff have a legal duty to treat you to a reasonable standard.
Breach of duty is showing that the care you received was worse than what a typical doctor or nurse would provide in the same situation. This could be your medical professional failing to get a senior opinion or sending you home without clear advice.
Causation is about proving the breach of duty directly led to your harm. You need to show that an earlier diagnosis or proper treatment would have made a substantial difference to your outcome.
You also need to show you suffered harm — whether that’s physical injury, worsening illness, financial losses, or more treatment. Medical records, test results, and staff notes are key to building your case.
Specialist medical negligence solicitor for A&E diagnostic errors
If you think a mistake in your A&E diagnosis has left you worse off, it’s worth talking to a specialist clinical negligence solicitor.
Our experts at Friends Legal can determine whether the treatment you received at A&E fell below the standard expected of medical professionals. Get in touch today for friendly legal advice. We’re here to listen and help you understand your options.
