Hereditary aceruloplasminemia (HA), related to mutations in the ceruloplasmin (Cp) gene, leads to iron accumulation. Ceruloplasmin ferroxidase activity being considered essential for macrophage iron release, macrophage iron overload is expected, but it is not found in hepatic and splenic macrophages in humans. Our objective was to get a better understanding of the mechanisms leading to iron excess in HA. A clustered regularly interspaced short palindromic repeats (CRISPR)/ CRISPR associated protein 9 (Cas9) knockout of the Cp gene was performed on Sprague-Dawley rats. We evaluated the iron status in plasma, the expression of iron metabolism genes, and the status of other metals whose interactions with iron are increasingly recognized. In Cp 2/2 rats, plasma ceruloplasmin and ferroxidase activity were absent, together with decreased iron concentration and transferrin saturation. Similarly as in humans, the hepatocytes were iron overloaded conversely to hepatic and splenic macrophages. Despite a relative hepcidin deficiency in Cp 2/2 rats and the loss of ferroxidase activity, potentially expected to limit the interaction of iron with transferrin, no increase of plasma non-transferrin-bound iron level was found. Copper was decreased in the spleen, whereas manganese was increased in the plasma. These data suggest that the reported role of ceruloplasmin cannot fully explain the iron hepatosplenic phenotype in HA, encouraging the search for additional mechanisms.-

Despite adjusted reference ranges for Freelite FLC ratio, there are approximately 12.5% discrepancies in interpretation of FLC ratio between the 2 available assays. They are not linked to renal failure stage and neither of the assays performed better than the other: results must be interpreted taking into account clinical data and the same assay must be used for patient follow-up.

Background Smoldering multiple myeloma (SMM) is an asymptomatic plasma cell disorder with a high risk of progression to symptomatic multiple myeloma (MM). The serum free light chain (sFLC) ratio is a powerful prognostic factor for SMM: an sFLC ratio ≥8 has been reported to be associated with a high risk of progression to MM, and an sFLC ratio ≥100 has been described as a criterion for ultra-high-risk SMM, and has been integrated into the definition criteria for MM since 2014. However, all recommendations were based on sFLC measured using the first commercialized assay, Freelite™, while other assays are now available. We aimed to evaluate the safety and accuracy of N-Latex sFLC to identify high-risk and ultra-high-risk SMM. Methods The sFLC ratio was measured at diagnosis with both Freelite and N-Latex assays in a cohort of 176 SMM patients on a BN Prospec nephelometer. Demographic, clinical, therapeutic and laboratory data were collected at the time of diagnosis and at follow-up. Results Sixty-two patients (35.2%) progressed to MM within 2 years. Compared to Freelite™ sFLC, N Latex sFLC ratios ≥8 and ≥100 provided similar performances for the identification of high-risk and ultra-high risk SMM patients. Conclusions Our results evidenced that the N-Latex assay could be used for SMM monitoring, like Freelite. However, an N-Latex sFLC ratio ≥70 appears to provide similar performances to a Freelite sFLC ratio ≥100, with a slightly better positive predictive value. Both assays provided accurate identification of high-risk and ultra-high risk SMM patients. These results should be confirmed in an independent study.

Background Smoldering multiple myeloma (SMM) is a precursor disease of multiple myeloma (MM). According to 2003 classification, the IMWG (International Myeloma Working Group) recommended only to treat patients with end organ damage - often referred as CRAB criteria (hypercalcemia, renal failure, anemia and radiological bone lesions). The standard of care for SMM was to postpone treatment until progression to symptomatic disease occurred. The average annual risk of progression of SMM to MM was 10%/year. In 2014 IMWG proposed a revised classification including 3 new criteria that enable early diagnosis of MM before organ damage. The new criteria of MM needs the presence of more than 10% clonal bone marrow plasma cells combined with either the presence of end organ damage (CRAB criteria) or one of following new biomarkers of malignancy: bone marrow plasma cells ≥60%, serum free light chains (FLC) ratio ≥100 and ≥2 focal lesions on MRI. The FLC criteria were established with Freelite™ assay (The Binding Site Company) and have not been validated with other available assays. Freelite™ assay which used polyclonal antibodies was available since 2001. More recently N Latex assay (Siemens Healthyneers) using monoclonal antibodies has been commercialized in Europe. It is now well know that there is a good correlation between the 2 assays even though results in absolute values are not numerically identical. In this context, the aim of this study was to evaluate the concordance between the two assays to identify high risk SMM, when considering the biomarker of malignancy FLC ratio ≥100. Methods This is a retrospective study including 185 patients with SMM according to 2003 IMWG criteria. FLC concentration and ratio were evaluated in frozen sera with both assays in a BN Prospec and evolution status was collected. Results The average age was 62.5 (± 10.2) years old. Results revealed poor correlation between the 2 assays with a Slope Passing-Bablok value of 0.63 (0.57-0.67) for the FLC κ and of 0.44 (0.35-0.62) for the κ/ λ ratio ≥ 100, and concordance in determining the level of FLC λ with a Slope Passing-Bablok 1.16 (0.99-1.40). A Freelite™ratio ≥ 100 was found in 27 patients (14.3%), and a N Latex ratio ≥ 100 was found in 10 patients (5.3%). All but one patients with an N Latex ratio ≥ 100 had also a Freelite™ ratio ≥ 100. Mean of follow up was 2.4 years. A progression toward MM was observed in 77 (40.7%) patients. Among the 27 patients with Freelite™ ratio ≥ 100, 14 patients (55.5%) have evolved toward MM (figure 1A). Specificity and sensitivity for a Freelite™ ratio ≥ 100 were respectively 88.7% (95% CI 81.8 to 94.0%) and 20.3% (95% CI 11.8 to 31.2%). With the N Latex Assay, only 10 patients had a FLC ratio ≥ 100, in which 7 patients have evolved towards MM. Specificity and sensitivity for a N-Latex ratio ≥ 100 were respectively be 67.0% (95% CI 57.4 to 75.6%) and 53.2% (95% CI 41.5 to 64.7%). Given the poor predictive performance of a N-Latex ratio ≥ 100 we determined that a N-Latex ratio ≥ 70 have adequate specificity of 95.5% (95% CI 89.9 to 98.5%) and a sensitivity of 13.0% (95% CI 6.4 to 22.6%) (figure 1B). 15 patients (8.1%) patients had a N-Latex ratio ≥ 70. Among these, 10 patients (66.6%) have evolved toward MM. Conclusion Our study shows poor correlation between the two FLC assays in SMM patients. A Freelite™ ratio ≥ 100 had a lesser specificity than previously described (specificity 95% in Larsen study [1]). The 100 cut-off value was not performant enough for N-Latex assay. A new ratio is thus needed and was found to be 70 to have sufficient specificity and sensitivity. This result need to be validated in an independent cohort. However, with a Freelite™ ratio ≥ 100 or an N Latex ratio ≥ 70, a significant number of patients would have been overtreated. Physicians should be aware of the limits of both assays. 1.Larsen JT, Kumar SK, Dispenzieri A, Kyle RA, Katzmann JA, Rajkumar SV. Serum free light chain ratio as a biomarker for high-risk smoldering multiple myeloma. Leukemia. 2013;27:941-6. Figure 1 probability of progression to overt multiple myeloma (A) according to Freelite™ ratio (cut-off 100) (B) according to N-Latex ratio (cut-off 70) Figure 1. probability of progression to overt multiple myeloma (A) according to Freelite™ ratio (cut-off 100) (B) according to N-Latex ratio (cut-off 70) Disclosures Moreau: The Binding Site: Other: supply of free light chain assays ; SIEMENS: Other: supply of free light chain assays , Research Funding. Decaux:The Binding Site: Other: supply of free light chain assays , Research Funding; SIEMENS: Honoraria, Other: supply of free light chain assays , Research Funding.