[zephyrus]

blood and urine tests seem contradictory

by zephyrus on Sun Sep 15, 2013 4:01 pm

My wife has light chain myeloma. 1 year after stem cell transplant, serum free light chain (SFLC) had normal kappa, lambda and ratio values. Kidney function was normal. 24 hour urine immunofixation (IFE) test showed evidence of kappa Bence-Jones protein. IFE is supposed to be about 15 times less sensitive than SFLC, so why does it see paraproteins in urine? And why just kappa light chains when there are almost as many lambda light chains in the blood? Isn’t the SFLC test the most sensitive one?

[Dr. Jason Valent]

Re: blood and urine tests seem contradictory

by Dr. Jason Valent on Mon Sep 16, 2013 10:55 am

Good question.

The serum free light chain test is very good at measuring disease response and monitoring control. The 24 hour urine is also a good test to monitor for small amounts of disease. Random urine IFE is not as sensitive as the 24 hour collection.

I think what you are seeing in your wife is just a very low (probably clinically insignificant) level of detectable disease in the urine. Something to be monitored but it is probably not necessary to change/restart treatment.

I hope this helps.