Dear Myeloma Community, Great day, I am 70 years old, diagnosed with Myeloma since almost two years. I am now on Lenalidomide 10mg maintenance dose. I am monitoring the Kappa Light Chains, being my type of disease, as an important marker for progression. I have no m-spike. The outcomes are different from Lab to Lab. Such as I got 129 from one lab and 89 from the other with 1 day difference between giving the blood samples. My question: did anybody come across the question of the accuracy/ tolerance of this test? Is it plus or minus 5%, 10% or? I am not able to judge or find an answer. My doctor says I don't need further tests like a Biopsy or PET, but we need to monitor my condition monthly. Please let me know if you have a similar situation or can help somehow with an advice. Rgds to all