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Abstract Hemodilution of bone marrow (BM) aspirates is a limitation of multiparameter flow cytometry (MFC) in plasma cell disorders. There is a need for a validated approach for assessing sample quality and the distribution of non-plasma cell BM populations by MFC could provide a solution. We evaluated BM-associated cell populations, assessed by next-generation flow cytometry (NGF) and white blood cell (WBC) count in 351 BM aspirated samples from 219 participants with plasma cell disorders in the Iceland Screens, Treats, or Prevents MM study (iStopMM), as markers of hemodilution by their discriminatory ability between first and (generally more hemodiluted) second pull BM aspirated samples. The most discriminating markers were used to derive a novel BM quality index (BMQI). Nucleated red blood cells and myeloid precursors provided the greatest discriminatory ability between first vs second pull samples (area under the curve (AUC): 0.87 and 0.85, respectively), significantly better than B cell precursors (AUC = 0.64; p

Abstract Serum free light chain (FLC) concentration is greatly affected by kidney function. Using a large prospective population-based cohort, we aimed to establish a reference interval for FLCs in persons with chronic kidney disease (CKD). A total of 75422 participants of the iStopMM study were screened with serum FLC, serum protein electrophoresis and immunofixation. Estimated glomerular filtration rate (eGFR) was calculated from serum creatinine. Central 99% reference intervals were determined, and 95% confidence intervals calculated. Included were 6461 (12%) participants with measured FLCs, eGFR

Abstract Multiple myeloma (MM) patients have increased risk of severe coronavirus disease 2019 (COVID-19) when infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Monoclonal gammopathy of undetermined significance (MGUS), the precursor of MM has been associated with immune dysfunction which may lead to severe COVID-19. No systematic data have been published on COVID-19 in individuals with MGUS. We conducted a large population-based cohort study evaluating the risk of SARS-CoV-2 infection and severe COVID-19 among individuals with MGUS. We included 75,422 Icelanders born before 1976, who had been screened for MGUS in the Iceland Screens Treats or Prevents Multiple Myeloma study (iStopMM). Data on SARS-CoV-2 testing and COVID-19 severity were acquired from the Icelandic COVID-19 Study Group. Using a test-negative study design, we included 32,047 iStopMM participants who had been tested for SARS-CoV-2, of whom 1754 had MGUS. Among these participants, 1100 participants, tested positive, 65 of whom had MGUS. Severe COVID-19 developed in 230 participants, including 16 with MGUS. MGUS was not associated with SARS-CoV-2 infection (Odds ratio (OR): 1.05; 95% confidence interval (CI): 0.81–1.36; p = 0.72) or severe COVID-19 (OR: 0.99; 95%CI: 0.52–1.91; p = 0.99). These findings indicate that MGUS does not affect the susceptibility to SARS-CoV-2 or the severity of COVID-19.

Abstract Monoclonal gammopathy of undetermined significance (MGUS) precedes multiple myeloma (MM). Population-based screening for MGUS could identify candidates for early treatment in MM. Here we describe the Iceland Screens, Treats, or Prevents Multiple Myeloma study (iStopMM), the first population-based screening study for MGUS including a randomized trial of follow-up strategies. Icelandic residents born before 1976 were offered participation. Blood samples are collected alongside blood sampling in the Icelandic healthcare system. Participants with MGUS are randomized to three study arms. Arm 1 is not contacted, arm 2 follows current guidelines, and arm 3 follows a more intensive strategy. Participants who progress are offered early treatment. Samples are collected longitudinally from arms 2 and 3 for the study biobank. All participants repeatedly answer questionnaires on various exposures and outcomes including quality of life and psychiatric health. National registries on health are cross-linked to all participants. Of the 148,704 individuals in the target population, 80 759 (54.3%) provided informed consent for participation. With a very high participation rate, the data from the iStopMM study will answer important questions on MGUS, including potentials harms and benefits of screening. The study can lead to a paradigm shift in MM therapy towards screening and early therapy.