A new study by scientists from UI and Landspítali University Hospital indicates that tens of thousands of people all over the world have probably been wrongly diagnosed with a multiple myeloma precursor condition. New definitions reduce the number of false-positive diagnoses by 80%.
The study, which was published recently in JAMA Oncology, is the largest of its kind in the world. It is based on data from over 75,000 Icelanders who took part in the iStopMM project – one of the largest medical research projects ever conducted in Iceland.
The project, which has twice received major ERC grants, is led by Sigurður Yngvi Kristinsson, professor at the UI Faculty of Medicine. The corresponding author of the paper presenting these fascinating findings is Þórir Einarsson Long, medical doctor and postdoctoral researcher.
False-positive diagnosis causes unnecessary anxiety
The method described in the paper is based on identifying a type of multiple myeloma precursor condition called light chain monoclonal gammopathy of undetermined significance – LC-MGUS. Some people who have this precursor condition go on to develop multiple myeloma, but most do not. However, many of those who are diagnosed with the precursor must undergo lifelong monitoring and in some cases extensive testing.
The problem is that the current reference intervals for so-called free light chains (FLC) in the blood, which are used to diagnose LC-MGUS, are imprecise, leading to widespread false-positive diagnosis. Many people have been informed that they have a precursor to a serious disease, when this is not actually true. Understandably, misdiagnosis of this kind has serious consequences both for individuals and society as a whole. So the revised definitions developed in this new study are a very positive change.
New reference intervals reduce false-positive diagnosis
Þórir Long explains that the team has proposed new definitions for LC-MGUS based on revised reference intervals for FLC, which are used to diagnose precursor conditions and related diseases. The new reference intervals take into account age and kidney function, factors which had not previously been considered.
“The study showed that when these new limits were used, the number of people diagnosed with LC-MGUS fell from 1.54% to 0.27%, which is a reduction of 82%. None of the people who had been misdiagnosed, according to these new reference intervals, later developed multiple myeloma or other related diseases,” says Þórir Long.
Important news for the healthcare system
“These findings indicate that a large group of people – in Iceland and abroad – have been misdiagnosed and monitored for years for no real reason. This has an impact on their quality of life. It causes anxiety, as well as an unnecessary burden on the healthcare system. By using the new limits, we are confident that only people who genuinely need to be monitored will be – and the other people can live their lives in peace,” says Sigurður Yngvi Kristinsson, professor at the UI Faculty of Medicine.
International impact of Icelandic research
This study is an offshoot of the iStopMM project, which is a collaboration between UI, Landspítali University Hospital and the Icelandic Cancer Society. The project has attracted global attention thanks to its findings about screening and prevention for multiple myeloma.
Already, iStopMM has begun to affect clinical guidelines across the world and could save healthcare systems billions in monitoring and testing costs – and above all reduce anxiety and uncertainty for people who have nothing to worry about.