I visit my oncologist once a quarter and have my FLC done there. In the interim months, I have the test done at another lab.
The lambda numbers run consistent, but I just noticed the kappa numbers do not. When tested at the oncologist visits, the numbers run in the 6-10 mg/L range (normal 3.3 to 19.4 mg/L), whereas at the other lab they are in the 2-3 range. This discrepancy has been consistent for about a year.
My problem is with the lambda numbers, but it does cause havoc with the ratios. Does anyone know if there is some subjectivity in scoring the results?
Thanks,
Forums
5 posts
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bgmiller80 - Name: Bob
- Who do you know with myeloma?: self
- When were you/they diagnosed?: 2010
- Age at diagnosis: 58
Re: Inconsistent FLC results between labs
Hi!
Rather than subjectivity in the interpretation of results, I suspect that differences from lab to lab occur because different free light chain "kits" are used to measure the FLC. In addition, different instruments may be used to run the FLC kits on. Also, having different technologists running the tests introduces another possible element of variability.
Variation in results from laboratory to laboratory is not a surprise and essentially a predictable finding. I see this almost every day in my practice. Ideally all results are run at the same expert laboratory.
Rather than subjectivity in the interpretation of results, I suspect that differences from lab to lab occur because different free light chain "kits" are used to measure the FLC. In addition, different instruments may be used to run the FLC kits on. Also, having different technologists running the tests introduces another possible element of variability.
Variation in results from laboratory to laboratory is not a surprise and essentially a predictable finding. I see this almost every day in my practice. Ideally all results are run at the same expert laboratory.
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Dr. Edward Libby - Name: Edward Libby, M.D.
Beacon Medical Advisor
Re: Inconsistent FLC results between labs
Bob,
To Dr. Libby's points, my onc is fine with me using any lab I want to have all my tests done, as long as I consistently use the same lab for my tests over time.
If you really want to get into the nits of things that can cause variation with the Freelite assay results, see:
J Tate et al, "Quantitative Serum Free Light Chain Assay – Analytical Issues," Clinical Biochemist Reviews, Aug 2009 (full text at Pubmed)
Abstract:
Serum free light chain (FLC) assay is an important advance in the diagnosis and monitoring of monoclonal light chain diseases and a complementary test to serum protein electrophoresis and immunofixation. Immunoturbidimetric and immunonephelometric assays for serum FLC are available on routine chemistry analysers and can detect FLC down to ~1 mg/L. These assays use polyclonal anti-human FLC antisera and require acceptable imprecision, specificity, accuracy, and reproducibility between reagent batches to prevent under- or over-estimation of FLC concentration.
Assay imprecision determined between reagent lots has a variation of 8–45% for FLC concentrations and 17–32% for the calculated κ/λ FLC ratio. Dilution studies indicate some over-recovery of FLC, which may depend upon the dilution matrix. However, greater discrepancies are underestimation from nonlinear reactions and overestimation possibly from interferences or multi-reactivity to polymeric FLC. Nonlinear monoclonal FLC give concentrations which are 2- to 6-fold increased at higher sample dilution and FLC measured on different platforms may not give the same results.
Laboratory staff and clinicians should be aware of the analytical limitations of the FLC assay. Assay imprecision, especially with different lots of FLC reagent, may have a significant effect on changes in the FLC concentration and κ/λ FLC ratio. Sample dilution anomalies have the potential to confound result interpretation for patients with monoclonal light chain disease. These issues, if not adequately appreciated, have the potential to mislead clinical diagnosis and assessment of response to therapy.
To Dr. Libby's points, my onc is fine with me using any lab I want to have all my tests done, as long as I consistently use the same lab for my tests over time.
If you really want to get into the nits of things that can cause variation with the Freelite assay results, see:
J Tate et al, "Quantitative Serum Free Light Chain Assay – Analytical Issues," Clinical Biochemist Reviews, Aug 2009 (full text at Pubmed)
Abstract:
Serum free light chain (FLC) assay is an important advance in the diagnosis and monitoring of monoclonal light chain diseases and a complementary test to serum protein electrophoresis and immunofixation. Immunoturbidimetric and immunonephelometric assays for serum FLC are available on routine chemistry analysers and can detect FLC down to ~1 mg/L. These assays use polyclonal anti-human FLC antisera and require acceptable imprecision, specificity, accuracy, and reproducibility between reagent batches to prevent under- or over-estimation of FLC concentration.
Assay imprecision determined between reagent lots has a variation of 8–45% for FLC concentrations and 17–32% for the calculated κ/λ FLC ratio. Dilution studies indicate some over-recovery of FLC, which may depend upon the dilution matrix. However, greater discrepancies are underestimation from nonlinear reactions and overestimation possibly from interferences or multi-reactivity to polymeric FLC. Nonlinear monoclonal FLC give concentrations which are 2- to 6-fold increased at higher sample dilution and FLC measured on different platforms may not give the same results.
Laboratory staff and clinicians should be aware of the analytical limitations of the FLC assay. Assay imprecision, especially with different lots of FLC reagent, may have a significant effect on changes in the FLC concentration and κ/λ FLC ratio. Sample dilution anomalies have the potential to confound result interpretation for patients with monoclonal light chain disease. These issues, if not adequately appreciated, have the potential to mislead clinical diagnosis and assessment of response to therapy.
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Multibilly - Name: Multibilly
- Who do you know with myeloma?: Me
- When were you/they diagnosed?: Smoldering, Nov, 2012
Re: Inconsistent FLC results between labs
Thanks for the insight. For the time being, I think I will go with the oncologist labs results. I will sleep a little bit better.
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bgmiller80 - Name: Bob
- Who do you know with myeloma?: self
- When were you/they diagnosed?: 2010
- Age at diagnosis: 58
Re: Inconsistent FLC results between labs
Hello bigmiller80.
I think it is important to always use the same lab when evaluating our myeloma numbers. I use a local oncology group to administer my treatment. However, I make the two hour drive every 90 days to have my myeloma labs done at the same lab used by my myeloma specialist. Since my local oncologist does not dictate my treatment plan, it serves no purpose to have her run anything other than a CBC and liver panel to monitor my tolerance to treatment.
It's always best to compare "apples to apples" and remove the doubt and worry associated with differences in lab results. I find it gives me peace of mind and confidence.
I think it is important to always use the same lab when evaluating our myeloma numbers. I use a local oncology group to administer my treatment. However, I make the two hour drive every 90 days to have my myeloma labs done at the same lab used by my myeloma specialist. Since my local oncologist does not dictate my treatment plan, it serves no purpose to have her run anything other than a CBC and liver panel to monitor my tolerance to treatment.
It's always best to compare "apples to apples" and remove the doubt and worry associated with differences in lab results. I find it gives me peace of mind and confidence.
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Dano - Who do you know with myeloma?: Me
- When were you/they diagnosed?: Jan 2014
- Age at diagnosis: 65
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