In practice, the number of samples that require redilution will be dependent on the number of samples from patients with monoclonal gammopathy. When the proportion of samples with monoclonal sFLCs increases, the frequency of samples with high results, and hence the number of redilutions will increase. Caillon et al. assessed the number of redilutions required to achieve a final result in a cohort of 113 LCMM patients. At baseline, only 11% and 5% of samples gave final results at the standard dilution for κ and λ, respectively. However, following 3 cycles of induction therapy, final results were generated at the standard dilution in 54% and 63% of κ and λ cases, respectively. Overall, the average number of redilutions required to give a final result per patient was 1.9. The authors comment that “laboratories should be reassured by the reduction in the need for redilutions in individual multiple myeloma patients after initiating treatment”.
In summary, >80% of routine samples give a final result at the initial dilution on the Optilite or SPAPLUS. sFLC measurements on other platforms, such as the BN™II, may require additional dilutions as they do not include inbuilt antigen excess parameters (Section 7.5) and have narrow measuring ranges (Section 6.1).