Arginine vasopressin (AVP) mediates water transport in the renal collecting ducts by forming water channels of aquaporin-2 (AQP2) in the apical plasma membrane. AQP2 is excreted in human urine. We wanted to test the hypothesis that urinary excretion of AQP2 (u-AQP2) reflects the effect of AVP on the renal collecting ducts during water deprivation and hypertonic saline infusion in healthy subjects. Fifteen healthy subjects underwent a 24-h period of fluid restriction. Urine and blood samples were collected at timed intervals. Fifteen healthy subjects were given 7 ml/kg 3% hypertonic saline infusion for 30 min. Urine and blood samples were collected at timed intervals. During fluid restriction, the u-AQP2 rate increased from 3.9 (25th percentile: 3.1; 75th percentile: 5.2) to 7.6 (5.9-9.1; P < 0.001) ng/min, and the plasma AVP (p-AVP) level increased from 0.5 (0.4-0.6) to 3 (1.7-3.3) pmol/l. There was a positive correlation between the maximum change in u-AQP2 rate and the maximum change in p-AVP (r = 0.57, P < 0.03). During the infusion study, u-AQP2 rate was at maximum 90 min after the infusion [baseline: 4.5 ng/min (3.5-4.8); 90 min: 5 ng/min (4.5-6.0) P < 0.02]. p-AVP increased from 1.0 (0.9-1.1) to 1.5 (1.2-1.8; P < 0.002) pmol/l. There was a positive correlation between the maximum change in u-AQP2 rate and the maximum change in p-AVP (r = 0.83; P < 0.0001). It can be concluded that p-AVP and u-AQP2 are increased during thirst and hypertonic saline infusion and that u-AQP2 reflects the action of AVP on the collecting ducts.

The results of our prospective study have revealed great diversity in the treatment regimens used to manage MM in real-life practice. This diversity was linked to factors such as novel agent accessibility and evolving treatment recommendations. Our results provide insight into associated clinical benefits.

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Several risk scores for disease progression in patients with smoldering multiple myeloma (SMM) have been proposed; however, all have been developed using single-center registries. To examine risk factors for time to progression (TTP) to multiple myeloma (MM) for SMM, we analyzed a nationwide population-based cohort of 321 patients with newly diagnosed SMM registered within the Danish Multiple Myeloma Registry between 2005 and 2014. Significant univariable risk factors for TTP were selected for multivariable Cox regression analyses. We found that both an M-protein ≥30 g/L and immunoparesis significantly influenced TTP (HR 2.7, 95%CI (1.5;4.7), P = 0.001, and HR 3.3, 95%CI (1.4;7.8), P = 0.002, respectively). High free light chain (FLC) ratio did not significantly influence TTP in our cohort. Therefore, our data do not support recent IMWG proposal of identifying patients with FLC ratio above 100 as having ultra high-risk of transformation to MM. Using only immunoparesis and M-protein ≥30 g/L, we created a scoring system to identify low-, intermediate-, and high-risk SMM. This first population-based study of patients with SMM confirms that an M-protein ≥30 g/L and immunoparesis remain important risk factors for progression to MM.

Immunoparesis (hypogammaglobulinemia) is associated to an unfavorable prognosis in newly diagnosed Multiple myeloma (MM) patients. However, this finding has not been validated in an unselected population-based cohort. We analyzed 2558 newly diagnosed MM patients in the Danish Multiple Myeloma Registry representing the entire MM population in Denmark from 2005–2013. Two-thousand two hundred and fifty three patients (90%) presented with reduction below lower normal levels of at least one uninvolved immunoglobulin. Using multivariable Cox regression we found that high age, high ISS score, high LDH and IgA MM were associated to both shorter overall survival and progression free survival. Furthermore, bone marrow plasma cell % was associated to short progression free survival. Immunoparesis had no independent significant effect on OS (HR 0.9 (95%CI: 0.7;1.0; p = 0.12)). Likewise, the number of suppressed immunoglobulins or the relative degree of suppressed uninvolved immunoglobulins from lower normal level (quantitative immunoparesis) was not associated to OS in the multivariable analysis. However, quantitative immunoparesis with at least 25% reduction (from lower normal level) of uninvolved immunoglobulins was associated to shorter PFS for the entire population. The impact of quantitative immunoparesis on PFS was present irrespective of calendar periods 2005–2008 and 2009–2013. Our population-based study does not confirm that immunoparesis at diagnosis is an independent prognostic factor regarding OS. However, quantitative immunoparesis is associated to a shorter PFS.