Change in serum free light chain testing

As of the 1st September 2020, Pathlab will be changing the instrumentation in which kappa and lambda serum free light chains are performed. Historically these tests have been performed using the SPA Plus and analysed using freelite reagent, both supplied by The Binding Site.

The Binding Site has recently released an upgraded instrument, the Optilite. This instrument uses the same freelite reagent to quantify kappa and lambda free light chains in human serum.

The reference intervals for both Kappa and Lambda will not change, however there may be an adjustment period in which patients may exhibit a change in value for kappa and lambda and the corresponding K/L ratio. As a result of this, patients who are being monitored monthly for disease and/or treatment response will have two reported results; one using the SPA Plus and one result from the Optilite. These patients will have two months of dual reporting in order to re-establish Kappa and Lambda values on the new Optilite instrumentation.

This will only include patients who are under the care of a Haematologist for myeloma or amyloid conditions. One off GP or sporadic requests for serum free light chains will only have one result reported from the Optilite.

Please see the reference intervals for both kappa and lambda free light chains and the expected ratio below.

Free kappa 3.3-19.4 mg/L
Free lambda 5.71-26.3 mg/L
K/L Ratio 0.26-1.65