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Professor Mark Drayson’s review of Seralite® – FLC

In this series of videos below, Professor Mark Drayson, Director at the University of Birmingham’s Clinical Immunology Service, discusses  Seralite®– FLC, a rapid lateral flow test for the quantification of kappa (K) and lambda (λ) immunoglobulin free light chains (FLCs) in serum.  Professor Drayson will cover the technical and clinical validation of Seralite®-FLC as well as some of the differences observed between different FLC methods.

Part 1: The identification and extensive validation of Seralite®– FLC monoclonal antibodies


More videos below

The transcript of ‘Part 1: Prof. Mark Drayson discusses Seralite® – FLC’

“Seralite is part of a second-generation of improved free light chain tests and they’re based on monoclonal antibodies that we developed here at the University of Birmingham. So within that stable, we’ve got Seralite, which is based on a lateral flow format. So it will simultaneously quantitate kappa and lambda free light chains levels with the same, or better, precision and accuracy as the conventional laboratory assays. And it’s not hindered by the problem that some of those lab assays have which is in antigen excess.”

“We’ve made many monoclonal antibodies that are specific for free light chains. But, quite a lot of them won’t identify all patients. So, we had to go through our whole bank of monoclonal antibodies against either free kappa or free lambda, and not only validate that they detected free light chains and didn’t detect light chains bound to whole immunoglobulin. We also had to test those monoclonals against a few thousand myeloma patients to be sure that picked up all of them. And so in our routine clinical practice, we’ve used these monoclonals, actually for detecting free light chains in urine over several years, during which time we’ve showed by the comparison with the gold standard  immunofixation of light chains in urine we showed that the monoclonals didn’t miss any of 6,500 patients.”

Part 2: The clinical validation of the monoclonal antibodies used in Seralite®-FLC


The transcript of ‘Part 2: Prof. Mark Drayson discusses Seralite® – FLC’

“To validate Seralite in Free Light Chain only patients and in Non Secretory patients, we took really an unprecedented number of patients, we had 576 Light Chain only patients. Then on top of that, we had a further 60 patients who were Non Secretory as defined by immunofix negative in serum and urine. So, when we look at can Seralite make the diagnosis in these patients? It had 100% sensitivity. So, the next question is, how does Seralite perform in assessing response to anti-myeloma therapy? and then how does it perform in assessing and monitoring patients during remission to see if they are relapsing?”

“We had 100% sensitivity and specificity on those questions looking at Seralite in, I suppose, at least a third of those 576 plus 60 patients. So, it measured response in Light Chain only patients with very good correlation with clinical findings and other laboratories findings and similarly identified relapse, again correlating very well with clinical and other laboratory features.”

Part 3: The differences observed between different Free Light Chain methods

The transcript of ‘Part 3: Prof. Mark Drayson discusses Seralite® – FLC’

“Yes, there are differences between free light chain assays, and I think most clinical chemists would expect that assays on different platforms in different laboratories to give slightly different results. The important thing is to fully assess what the differences are and what the clinical significance of the differences. The free light chain assays we have available across the world at the moment, generally speaking, will give very good agreement on the milligrams per litre of kappa or lambda in normal healthy people. They’ll be subtle differences in reference ranges for the kappa and lambda mgs per litre and the kappa/lambda ratio, but there won’t be big differences and generally, there will be a very good agreement.”

“I would say in general Freelite tends to give you a much higher milligrams per litre result than Seralite would. The important thing is can you detect the patient with sensitivity and specificity? And, can you then detect changes in disease activity by a percentage decrease or a percentage increase in the free light chain difference? And that works very well between the assays.”

“When it comes to myeloma and other plasma cell dyscrasia patients it is important to apply the results to the reference ranges for that assay and it is also important to know what the cut points for that particular assay are.”

Part 4: How to switch between different Free Light Chain methods

The transcript of ‘Part 4: Prof. Mark Drayson discusses Seralite® – FLC’

“Well, the differences are small. I think the first thing is to check, if you are going to change from one assay to another, you have to check the literature and you also have to assess what the reference ranges are and the cut points for the different disease events should be for the assay that you’re changing to.”

“For new patients, it’s not a problem because we’ve fully validated the validity of Seralite and its sensitivity and specificity for diagnosing a new patient, and similarly for measuring response to therapy and for detecting relapse from remission.”

“But, if you’ve been using one assay method for monitoring patients for a long time, then you are going to convert to a new assay, you know the new assay is going to give slightly different results. So, you have to do one of two things; when a new sample comes in for that patient, you either have to measure it on your old assay method and your new assay method together so that you can show the change in the baseline as you carry on monitoring that patient. Or you, as we would do, because we’ve got stored samples from the last sample, in fact, we don’t throw away samples for many years, we go back to the last sample and we measure it with the new sample with our new Seralite assay”