What is an SAP scan?
SAP (Serum amyloid P component) is a protein found in the blood that binds to amyloid deposits. Normally only small amounts of SAP are present in the blood but in patients with systemic amyloidosis large quantities can be found on amyloid deposits. During an SAP scan, a small amount of SAP from a healthy blood donor is tagged with a radioactive tracer (a radioisotope called Iodine-123), and injected into the patient. The tagged SAP then reveals the location of the amyloid deposits as it binds to them.
SAP scanning is most useful as a monitoring tool in AA amyloidosis, where it can track whether deposits are growing or regressing in response to treatment, and in AL amyloidosis where it maps organ involvement. Diagnostic sensitivity is around 90% for both types. SAP scanning tends to be considerably less effective for hereditary ATTR amyloidosis where sensitivity drops to only around 48% and is therefore not the primary monitoring tool for that type of amyloidosis.
SAP scans are currently only offered in London at the National Amyloidosis Centre (NAC) and in the Netherlands at the University Medical Centre Groningen (UMCG).
Why are SAP scans unavailable in the UK right now?
As some of our community are already aware, SAP scans have been unavailable at the NAC since at least early 2025. This is an ongoing issue that has been raised to us by numerous patients and carers, understandably.
The unavailability of the SAP scans comes down to a global shortage of medical radioactive isotopes caused largely by aging reactors—those that provide 95% of the world’s supply—beginning to fail. A proposal is in place to build a small nuclear facility to manufacture these radioisotopes within the UK rather than relying on imports, but that would not be online until 2030 at the earliest.
In August 2025, the NAC informed us there would be no SAP scans taking place there until February or March 2026 at the earliest. As of today the situation remains unchanged, even though the supply issue has been debated in Parliament. Since these radioisotopes are used not only in the SAP scan but also in all kinds of cancer screening and other diagnostic processes, the issue is considered critical.
How important are SAP scans to amyloidosis patients?
We consulted with our clinical expert to clarify just how crucial the SAP scans are specifically for amyloidosis care and diagnosis. She pointed out a few key facts that we want to make our community aware of as the subject is more nuanced than it may appear.
Although SAP scans are highly useful for monitoring people’s responses to treatments over time, the same can also be achieved through blood tests. In other words, SAP scans aren’t a dealbreaker for patients and don’t significantly impact care—they’re more of an advanced tool to provide higher fidelity monitoring.
Also, people are still able to get their amyloidosis diagnoses regardless of the scans. The real danger is that some physicians may question the point of sending their patients to the NAC if the SAP scans aren’t available. Because the NAC offers a lot more than SAP scans in terms of care and monitoring, that would be a most unfortunate result for those patients so we want to prevent that from happening.
What can you do?
We share people’s frustration with the situation and the wider impacts on other conditions that rely on medical radioisotopes to a greater extent. What we do know for certain is that this is beyond the NAC or the NHS, it is a larger matter for the government to resolve. Still, if you are passionate about making sure this situation improves as soon as possible, then it certainly would help to write to both your MP and the health minister. Each letter sent to an MP is often considered to represent the views of thousands who are less inclined to write so it will have an impact.
