There is a “clear and urgent” need to improve NHS screening to work out who may benefit from new Alzheimer’s drugs, according to a study.

Experts found that just 14% of people screened in specialist clinics may end up benefiting from the drugs, but the tests needed to confirm diagnosis of Alzheimer’s – such as fluid biomarker tests or PET scans – are not easily available on the NHS.

A new crop of drugs, lecanemab and donanemab, slow down early stages of the disease and are currently being assessed for approval in the UK by medicine regulators.

They mark a step-change in treatment because they target one of the known causes of Alzheimer’s, rather than just helping to relieve symptoms.

A new study in the Journal of Neurology, Neurosurgery and Psychiatry has analysed who may actually benefit from the drugs, and how this compares to screening.

Researchers including from University College London (UCL) and several NHS trusts examined clinical notes from 1,017 patients in five areas of London, including 517 patients assessed in memory services and 500 in a specialist cognitive service.

The data showed that 32% (163) of patients in memory services were likely to be referred for potential suitability for the drugs.

Of these, 161 patients had undergone neuroimaging, but fluid biomarker tests were carried out in only two patients.

The researchers said: “A secure diagnosis of Alzheimer’s disease with beta-amyloid accumulation is only possible with fluid biomarkers or PET imaging, which are currently not usually available to memory services within the UK; a clear and urgent area for improvement.”

Elsewhere, in the specialist clinics where more tests are available, most people (492) had been given scans to diagnose Alzheimer’s.

Fluid biomarker tests were also performed in nearly two thirds (62%) of those with Alzheimer’s disease.

After excluding people due to frailty and other issues that made them not suitable for treatment, some 40% of Alzheimer’s patients were potentially eligible for treatment with the new drugs.

The researchers said this is equivalent to just 14% of all the cases reviewed at the specialist cognitive clinics.

They said NHS systems “need to be set up to deal with this potential large mismatch between referral and ultimate eligibility in order to avoid overwhelming services”.

They added a “significant issue is that due to the lack of biomarker testing in community memory clinics, the clinical suspicion of Alzheimer’s is likely to be incorrect in at least 30% of cases”.

David Thomas, head of policy and public affairs at Alzheimer’s Research UK, said: “New Alzheimer’s drugs are finally on the horizon, but for their full potential to be realised, health systems need to be able to offer people with symptoms of dementia an accurate and early diagnosis to find out whether these treatments could benefit them.

“As this research demonstrates, the NHS is a long way from being able to do this testing routinely.

“Whoever forms the next government must invest in the NHS urgently, to ensure we have the right diagnostics and workforce in place to help identify people who could benefit from new treatments should they be deemed safe and effective by the regulators.

“A key part of the solution is cheaper, more scalable diagnostics, such as blood tests, for use in clinical care.”

Dr Alex Osborne, policy manager at the Alzheimer’s Society, said: “These drugs are only available to people in the early stages of Alzheimer’s disease – and more than a third of the 982,000 people living with dementia in the UK don’t have a diagnosis at all.

“That’s why Alzheimer’s Society is calling on the NHS to publish plans on how it will deliver groundbreaking new treatments to the people who need them, with a specific focus on diagnosis and investment in the tools and workforce needed to identify eligible patients.”

A report published earlier this year by NHS England said “timely diagnosis of dementia is vital”.

It put the costs of implementing the new drugs – if they are approved – at an estimated £500 million and £1 billion per year.

However, actual costs will depend on the drugs prices agreed for England.

The document said: “To be eligible for treatment, patients will need to have a baseline MRI scan and then either a PET-CT scan or lumbar puncture that confirms the presence of beta-amyloid proteins in the brain, which are associated with the Alzheimer’s disease process.”

It said new biomarker-based blood tests may be available in the future to screen patients and “this means we should be cautious about driving a massive expansion, for example in amyloid PET-CT capacity, when this could become redundant in the longer-term.”

The document said the estimated number of patients who might be deemed eligible for the drugs ranges from 50,000 to 280,000.