ISS I was defined as serum β2-microglobulin level <3.5mg/L and serum albumin level ≥3.5g/dL; ISS II included all patients with neither stage I or III; ISS III was defined as serum β2-microglobulin level ≥5.5mg/L, irrespective of serum albumin level.2 (link)Bone marrow plasma cells (BMPC) for iFISH analyses were enriched using anti-CD138-coated magnetic MicroBeads and AutoMACS Pro Separator (Miltenyi Biotech) following manufacturer’s instructions. BMPC were then fixed in Carnoy’s solution and stored at −20°C. Slides for iFISH were prepared using probes purchased from Cytocell, Kreatech and Vysis, according to manufacturer’s instructions. The routine panel included baseline evaluation of deletion(13), deletion(17p) and IgH translocations. Nuclei were analyzed using a fluorescent light microscope. 100–200 BMPC nuclei from each sample were scored. Deletion(17p) and/or translocation t(4;14) and/or translocation t(14;16) detected by iFISH were considered high-risk CA. Patients were considered positive for a given chromosomal abnormality when it was present in a percentage higher than the cut-off threshold, defined by each local laboratory. Details of inter-laboratory variability were reported in the Supplementary Methods.
Serum LDH level was recorded at baseline and classified as normal or high according to the local laboratory definition of normal range. High LDH was defined as serum level above the upper limit of normal range; normal LDH as serum level below the upper limit of normal (Table 1).